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Sample records for bright radio-quiet quasar

  1. On the peculiar X-ray properties of the bright nearby radio-quiet quasar PDS456

    OpenAIRE

    Vignali, C; Comastri, A.; F. Nicastro; Matt, G.; Fiore, F.; Palumbo, G. G. C.

    2000-01-01

    BeppoSAX and ASCA observations of the nearby (z=0.184), high-luminosity, radio-quiet quasar PDS456 are presented. The X-ray spectrum is characterized by a prominent ionized edge at 8-9 keV (originally discovered by RXTE, Reeves et al. 2000) and by a soft excess below 1.5 keV. The lack of any significant iron K alpha emission line suggests for the edge an origin from line-of-sight material rather than from reflection from a highly ionized accretion disc. The hard X-ray continuum is indeed well...

  2. On the peculiar X-ray properties of the bright nearby radio-quiet quasar PDS456

    CERN Document Server

    Vignali, C; Nicastro, F; Matt, G; Fiore, F; Palumbo, G G C

    2000-01-01

    BeppoSAX and ASCA observations of the nearby (z=0.184), high-luminosity, radio-quiet quasar PDS456 are presented. The X-ray spectrum is characterized by a prominent ionized edge at 8-9 keV (originally discovered by RXTE, Reeves et al. 2000) and by a soft excess below 1.5 keV. The lack of any significant iron K alpha emission line suggests for the edge an origin from line-of-sight material rather than from reflection from a highly ionized accretion disc. The hard X-ray continuum is indeed well modelled by transmission through a highly-ionized medium with a large column density (N_H warm = 4.5 x 10^24 cm^-2) plus an additional cold absorber with a lower column density (N_H cold = 2.7 x 10^22 cm^-2).

  3. Discovery of Universal Elliptical Outflow Structures in Radio-Quiet Quasars

    CERN Document Server

    Lovegrove, Justin; Leiter, Darryl

    2010-01-01

    Fifty-nine quasars in the background of the Magellanic Clouds had brightness records monitored by the MACHO project during the years 1992 - 99. Because the circumpolar fields of these quasars had no seasonal sampling defects, their observation produced data sets well suited to further careful analysis. Following a preliminary report wherein we showed the existence of reverberation in the data for one of the radio-quiet quasars in this group, we now show that similar reverberations have been seen in all of the 55 radio-quiet quasars with adequate data, making possible the determination of the quasar inclination to the observer's line of sight. The reverberation signatures indicate the presence of large-scale elliptical outflow structures similar to that predicted by the Elvis (2000) and "dusty torus" models of quasars, whose characteristic sizes vary within a surprisingly narrow range of scales. More importantly the observed opening angle relative to the polar axis of the universal elliptical outflow structure...

  4. The radio structure of radio-quiet quasars

    CERN Document Server

    Leipski, C; Bennert, N; Hüttemeister, S; Leipski, Christian; Falcke, Heino; Bennert, Nicola; Huettemeister, Susanne

    2006-01-01

    We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies. We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert galaxies. Many of the low redshift radio-quiet quasars show radio structures that can be interpreted as jet-like outflows. However, the detection rate of extended radio structures on arcsecond scales among our sample decreases with increasing redshift and luminosity, most likely due to a lack of resolution. The morphologies of the detected radio emission indicate strong interactions of the jets with the surrounding medium. We also compare the radio data of seven quasars with corresponding HST images of the [OIII] emitting narrow-line region (NLR). We find that the scenario of interaction between the radio jet and the NLR gas is confirmed in two sources by structures in the NLR gas distribution as previously known for Seyfert galaxies. ...

  5. Observations of feedback from radio-quiet quasars - I. Extents and morphologies of ionized gas nebulae

    Science.gov (United States)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.; Nesvadba, Nicole P. H.; Liu, Xin

    2013-04-01

    Black hole feedback - the strong interaction between the energy output of supermassive black holes and their surrounding environments - is routinely invoked to explain the absence of overly luminous galaxies, the black hole versus bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. In this paper, we present Gemini Integral Field Unit observations of the distribution of ionized gas around luminous, obscured, radio-quiet quasars at z ˜ 0.5. We detect extended ionized gas nebulae via [O III] λ5007 Å emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round, with Hβ surface brightness declining ∝R-3.5 ± 1.0. The regular morphologies of nebulae around radio-quiet quasars are in striking contrast with lumpy or elongated [O III] nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and type 2 quasars spanning six orders of magnitude in luminosity and confirm the flat slope of the correlation (R_{[O III]}∝ L_{[O III]}^{0.25± 0.02}). We propose a model of clumpy nebulae in which clouds that produce line emission transition from being ionization-bounded at small distances from the quasar to being matter-bounded in the outer parts of the nebula. The model - which has a declining pressure profile - qualitatively explains line ratio profiles and surface brightness profiles seen in our sample. It is striking that we see such smooth and round large-scale gas nebulosities in this sample, which are inconsistent with illuminated merger debris and which we suggest may be the signature of accretion energy from the nucleus reaching gas at large scales.

  6. Star formation in quasar hosts and the origin of radio emission in radio-quiet quasars

    CERN Document Server

    Zakamska, Nadia L; Petric, Andreea; Dicken, Daniel; Greene, Jenny E; Heckman, Timothy M; Hickox, Ryan C; Ho, Luis C; Krolik, Julian H; Nesvadba, Nicole P H; Strauss, Michael A; Geach, James E; Oguri, Masamune; Strateva, Iskra V

    2015-01-01

    Radio emission from radio-quiet quasars may be due to star formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a wide-angle radiatively-driven outflow. In this paper we examine whether radio emission from radio-quiet quasars is a byproduct of star formation in their hosts. To this end we use infrared spectroscopy and photometry from Spitzer and Herschel to estimate or place upper limits on star formation rates in hosts of ~300 obscured and unobscured quasars at z<1. We find that low-ionization forbidden emission lines such as [NeII] and [NeIII] are likely dominated by quasar ionization and do not provide reliable star formation diagnostics in quasar hosts, while PAH emission features may be suppressed due to the destruction of PAH molecules by the quasar radiation field. While the bolometric luminosities of our sources are dominated by the quasars, the 160 micron fluxes are likely dominated by star formation, but they too should...

  7. Herschel-ATLAS: Far-infrared properties of radio-loud and radio-quiet quasars

    CERN Document Server

    Kalfountzou, E; Jarvis, M J; Hardcastle, M J; Smith, D J B; Bourne, N; Dunne, L; Ibar, E; Eales, S; Ivison, R J; Maddox, S; Smith, M W L; Valiante, E; de Zotti, G

    2014-01-01

    We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Im- ages Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-micron luminosity with respect to radio-quiet quasars with ...

  8. Discovery of universal outflow structures above and below the accretion disc plane in radio-quiet quasars

    Science.gov (United States)

    Lovegrove, Justin; Schild, Rudolph E.; Leiter, Darryl

    2011-04-01

    59 quasars in the background of the Magellanic Clouds had brightness records monitored by the MACHO project during the years 1992-99. Because the circumpolar fields of these quasars had no seasonal sampling defects, their observation produced data sets well suited to further careful analysis. Following a preliminary report wherein we showed the existence of reverberation in the data for one of the radio-quiet quasars in this group, we now show that similar reverberations have been seen in all of the 55 radio-quiet quasars with adequate data, making possible the determination of the quasar inclination to the observer's line of sight. The reverberation signatures indicate the presence of large-scale elliptical outflow structures similar to that predicted by the Elvis and 'dusty torus' models of quasars, whose characteristic sizes vary within a surprisingly narrow range of scales. More importantly, the observed opening angle relative to the polar axis of the universal elliptical outflow structure present was consistently found to be on the order of 78°.

  9. A search for rapid optical variability in radio-quiet quasars

    CERN Document Server

    Rabbette, M; Smith, N; Steel, S

    1998-01-01

    The detection of rapid variability on a time-scale of hours in radio-quiet quasars (RQQSOs) could be a powerful discriminator between starburst, accretion disc and relativistic jet models of these sources. This paper contains an account of a dedicated search for rapid optical variability in RQQSOs. The technique used differential photometry between the RQQSO and stars in the same field of view of the CCD. The 23 RQQSOs that were observed all have high luminosities (-27 1. The total amount of observation time was about 60 hours and these observations are part of an ongoing programme, started in September 1990, to search for rapid variability in RQQSOs. No evidence for short-term variability greater than about 0.1 magnitudes was detected in any of the 23 sources, however long-term variability was recorded for the radio-quiet quasar PG 2112+059. The finding charts are included here because they identify the RQQSO and the reference stars used in the photometry, and hence are available for use by other observers.

  10. Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars-IV

    CERN Document Server

    Kumar, Parveen; Gopal-Krishna,

    2016-01-01

    We report an extension of our program to search for radio-quiet BL Lac candidates using intra-night optical variability (INOV) as a probe. The present INOV observations cover a well-defined representative set of 10 `radio-quiet weak-emission-line quasars' (RQWLQs), selected from a newly published sample of 46 such sources, derived from the Sloan Digital Sky Survey (Data release 7). Intra-night CCD monitoring of the 10 RQWLQs was carried out in 18 sessions lasting at least 3.5 hours. For each session, differential light curves (DLCs) of the target RQWLQ were derived relative to two steady comparison stars monitored simultaneously. Combining these new data with those already published by us for 15 RQWLQs monitored in 30 sessions, we estimate an INOV duty cycle of $\\sim 3\\%$ for the RQWLQs, which appears inconsistent with BL Lacs. However, the observed INOV events (which occurred in just two of the sessions) are strong (with a fractional variability amplitude $\\psi >$ 10\\%), hence blazar-like. We briefly point o...

  11. Intranight optical variability of radio-quiet weak emission line quasars - IV

    Science.gov (United States)

    Kumar, Parveen; Chand, Hum; Gopal-Krishna

    2016-09-01

    We report an extension of our programme to search for radio-quiet BL Lac candidates using intranight optical variability (INOV) as a probe. The present INOV observations cover a well-defined representative set of 10 `radio-quiet weak-emission-line quasars' (RQWLQs), selected from a newly published sample of 46 such sources, derived from the Sloan Digital Sky Survey (Data release 7). Intranight CCD monitoring of the 10 RQWLQs was carried out in 18 sessions lasting at least 3.5 h. For each session, differential light curves of the target RQWLQ were derived relative to two steady comparison stars monitored simultaneously. Combining these new data with those already published by us for 15 RQWLQs monitored in 30 sessions, we estimate an INOV duty cycle of ˜3 per cent for the RQWLQs, which appears inconsistent with BL Lacs. However, the observed INOV events (which occurred in just two of the sessions) are strong (with a fractional variability amplitude ψ > 10 per cent), hence blazar-like. We briefly point out the prospects of an appreciable rise in the estimated INOV duty cycle for RQWLQs with a relatively modest increase in sensitivity for monitoring these rather faint objects.

  12. Observations of Feedback from Radio-Quiet Quasars: I. Extents and Morphologies of Ionized Gas Nebulae

    CERN Document Server

    Liu, Guilin; Greene, Jenny E; Nesvadba, Nicole P H; Liu, Xin

    2013-01-01

    Black hole feedback -- the strong interaction between the energy output of supermassive black holes and their surrounding environments -- is routinely invoked to explain the absence of overly luminous galaxies, the black hole vs. bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. We present Gemini IFU observations of the distribution of ionized gas around luminous, obscured, radio-quiet (RQ) quasars at z~0.5. We detect extended ionized gas nebulae via [O III]5007 emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round. The regular morphologies of nebulae around RQ quasars are in striking contrast with lumpy or elongated nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and type 2 quasars spanning 6 orders of ma...

  13. Observations of Feedback from Radio-Quiet Quasars: II. Kinematics of Ionized Gas Nebulae

    CERN Document Server

    Liu, Guilin; Greene, Jenny E; Nesvadba, Nicole P H; Liu, Xin

    2013-01-01

    The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around eleven luminous, obscured, radio-quiet quasars at z~0.5 out to ~15 kpc from the quasar; specifically, we measure the kinematics and morphology of [O III]5007 emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80% of the emission as high as 1000 km/s combined with relatively small velocity difference across them (from 90 to 520 km/s) point toward wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km/s, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly toward outer parts of the nebulae (by 3% per kpc on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, s...

  14. IFU Observations of Feedback from Radio-Quiet Quasars at 0.5

    Science.gov (United States)

    Liu, Guilin; Zakamska, N. L.; Greene, J. E.; Nesvadba, N.; Liu, X.

    2014-01-01

    Feedback from black holes is now understood to be a key ingredient in galaxy formation modeling, but direct probes of this process in action are scarce and limited to small samples of active nuclei. Meanwhile, theories have long predicted an evolutionary scenario in which galaxy mergers induce both star formation and nuclear activity, triggering a violent transition from an obscured accretion stage to an unobscured phase as a Type 1 quasar, yet direct evidence is lacking. We present Gemini Integral Field Unit (IFU) observations of the distribution of warm ionized gas 104 K) around two luminous radio-quiet quasars: 11 obscured (Type 2) and 12 unobscured (Type 1) quasars with matched [O III]5007 luminosities (L[O III] > 1042.7-43.6 erg/s) and redshifts ( 0.5). For the Type 2 quasar sample, we have found that their gas nebulae are: (1) existent and extended on galactic scales in every case (15-39 kpc across); (2) nearly perfectly round, in striking contrast with lumpy and/or elongated nebulae around radio galaxies; (3) signifying wide-angle quasi-spherical outflows by their roundness and large velocity dispersion (FWHM˜1000 km/s); (4) likely escaping from the host galaxies (the derived median outflow velocity is 760 km/s); (5) showing slightly declining velocity dispersions toward their outer parts (˜3% per kpc); (6) blowing winds with high kinetic energy (1045 erg/s, ˜2% of Lbol) and mass (2×103-4 M⊙/yr) flows. (7) showing a universal radial profile of [O III]/Hβ (8) constructing a size-luminosity relation with a flat slope, implying clumpy nebulae that transition from being ionization-bounded at small radii to being matter-bounded in the outer parts. For the Type 1 quasar sample, we also detect extended nebulae surrounding all quasars with sizes, morphology and gas kinematics surprisingly similar to the Type 2 quasar nebulae. In conclusion, energetic quasi-spherical outflows are ubiquitous in luminous quasars of all types at 0.5. Such striking smooth and

  15. Observations of feedback from radio-quiet quasars - II. Kinematics of ionized gas nebulae

    Science.gov (United States)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.; Nesvadba, Nicole P. H.; Liu, Xin

    2013-12-01

    The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around 11 luminous, obscured, radio-quiet quasars at z ˜ 0.5 out to ˜15 kpc from the quasar; specifically, we measure the kinematics and morphology of [O III] λ5007 Å emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80 per cent of the emission as high as 103 km s-1) combined with relatively small velocity difference across them (from 90 to 520 km s-1) point towards wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km s-1, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly towards outer parts of the nebulae (by 3 per cent kpc-1 on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, signifying gas outflows. For the median outflow velocity, we find dot{E}_kin between 4 × 1044 and 3 × 1045 erg s-1 and dot{M} between 2 × 103 and 2 × 104 M⊙ yr-1. These values are large enough for the observed quasar winds to have a significant impact on their host galaxies. The median rate of converting bolometric luminosity to kinetic energy of ionized gas clouds is ˜2 per cent. We report four new candidates for `superbubbles' - outflows that may have broken out of the denser regions of the host galaxy.

  16. Unveiling the origin of the radio emission in radio-quiet quasars

    CERN Document Server

    Ruiz, Noelia Herrera; Norris, Ray P; Maini, Alessandro

    2016-01-01

    The origin of the radio emission in radio-quiet quasars (RQQs) has been a matter of debate for a long time. It is not well understood whether the emission is caused by star formation in the host galaxy or by black hole activity of the active galactic nuclei (AGN). We shed some light on these questions using the Very Long Baseline Interferometry (VLBI) technique to search for RQQs in the field of the Cosmological Evolution Survey (COSMOS). The extensive multi-wavelength coverage of the field (from radio to X-rays) was used to classify RQQs, and the milli-arcsecond resolution of VLBI provides a direct way to identify AGNs. In a sample of 18 RQQs we detected 3 using the Very Long Baseline Array (VLBA) at 1.4 GHz. In this letter we report for the first time on a sample of RQQs with a measured lower limit on the fraction of radio emission coming from the AGN, thus demonstrating that the radio emission of at least some RQQs is dominated by an AGN.

  17. Exploratory X-ray Monitoring of Luminous Radio-Quiet Quasars at High Redshift: Initial Results

    CERN Document Server

    Shemmer, Ohad; Paolillo, Maurizio; Kaspi, Shai; Vignali, Cristian; Stein, Matthew S; Lira, Paulina; Schneider, Donald P; Gibson, Robert R

    2014-01-01

    We present initial results from an exploratory X-ray monitoring project of two groups of comparably luminous radio-quiet quasars (RQQs). The first consists of four sources at 4.10 <= z <= 4.35, monitored by Chandra, and the second is a comparison sample of three sources at 1.33 <= z <= 2.74, monitored by Swift. Together with archival X-ray data, the total rest-frame temporal baseline spans ~2-4 yr and ~5-13 yr for the first and second group, respectively. Six of these sources show significant X-ray variability over rest-frame timescales of ~10^2 - 10^3 d; three of these also show significant X-ray variability on rest-frame timescales of ~1-10 d. The X-ray variability properties of our variable sources are similar to those exhibited by nearby and far less luminous active galactic nuclei (AGNs). While we do not directly detect a trend of increasing X-ray variability with redshift, we do confirm previous reports of luminous AGNs exhibiting X-ray variability above that expected from their luminosities...

  18. An Investigation into the Effects of Luminosity on the Mid-Infrared Spectral Energy Distributions of Radio-Quiet Quasars

    CERN Document Server

    Gallagher, S C; Lacy, M; Hines, D C; Elitzur, M; Storrie-Lombardi, L J

    2007-01-01

    We present an analysis of the effects of luminosity on the shape of the mid-infrared spectral energy distributions (SEDs) of 234 radio-quiet quasars originally presented by Richards et al. In quasars without evident dust extinction, the spectrally integrated optical and infrared luminosities are linearly correlated over nearly three decades in luminosity. We find a significant (>99.99% confidence) correlation between the 1.8-8.0 micron spectral index and infrared luminosity that indicates an enhancement of the mid-infrared continuum with increasing luminosity. Coupled with strong evidence for spectral curvature in more luminous quasars, we conclude this trend is likely a manifestation of the `near-infrared (3-5 micron) bump' noticed in earlier quasar SED surveys. The strength of this feature is indicative of the contribution of emission from the hottest (>1000 K) dust to the mid-infrared spectrum; higher luminosity quasars tend to show more hot dust emission. Finally, the comparable distribution of bolometric...

  19. 3C 57 as an Atypical Radio-Loud Quasar: Implications for the Radio-Loud/Radio-Quiet Dichotomy

    CERN Document Server

    Sulentic, J W; Marziani, P; del Olmo, A; Stirpe, G M; Zamfir, S; Plauchu-Frayn, I

    2015-01-01

    Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among Type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar "main sequence" with both extreme optical FeII emission (R_{FeII} ~ 1) and a large CIV 1549 profile blueshift (~ -1500 km/s). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year ...

  20. 3C 57 as an atypical radio-loud quasar: implications for the radio-loud/radio-quiet dichotomy

    Science.gov (United States)

    Sulentic, J. W.; Martínez-Carballo, M. A.; Marziani, P.; del Olmo, A.; Stirpe, G. M.; Zamfir, S.; Plauchu-Frayn, I.

    2015-06-01

    Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar `main sequence' with both extreme optical Fe II emission (R_{Fe II} ˜ 1) and a large C IV λ1549 profile blueshift (˜-1500 km s-1). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year time-scale consistent with compact steep-spectrum (or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/LEdd quasars, we suggest that 3C 57 is an evolved RL quasar (i.e. large blackhole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong Fe II emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low-redshift source and resultant unusually high Eddington ratio giving rise to the atypical C IV λ1549.

  1. SDSS J0159+0105: A Radio-Quiet Quasar with a Centi-Parsec Supermassive Black Hole Binary Candidate

    CERN Document Server

    Zheng, Zhen-Ya; Shen, Yue; Jiang, Linhua; Wang, Jun-Xian; Chen, Xian; Cuadra, Jorge

    2015-01-01

    We report a candidate centi-parsec supermassive black hole binary (SMBHB) in the radio-quiet quasar SDSS J0159+0105 at z=0.217. The 8.1-year Catalina V-band light curve for this quasar reveals two significant (at P>99%) periodic signals at ~741 day and ~1500 day. The period ratio, which is close to 1:2, is typical of a black-hole binary system with a mass ratio of 0.05quasars. The UV excess indicates the existence of a mini-disk around each BH of the binary. SDSS J0159+0105 also has two SDSS spectroscopic observations separated by ~10 years. There is a significant change in the broad H-beta profile between the two epochs, which can be explained by a single broad-line region (BLR) around the binary system illuminated by the aforementioned mini-disks, or a stream of gas flowing from the c...

  2. Storm in a "Teacup": a radio-quiet quasar with ~10kpc radio-emitting bubbles and extreme gas kinematics

    CERN Document Server

    Harrison, C M; Alexander, D M; Bauer, F E; Edge, A C; Hogan, M T; Mullaney, J R; Swinbank, A M

    2014-01-01

    We present multi-frequency (1-8 GHz) VLA data, combined with VIMOS IFU data and HST imaging, of a z=0.085 radio-quiet type 2 quasar (with L(1.4GHz)~5e23 W/Hz and L(AGN)~2e45 erg/s). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the Teacup AGN in the literature. We identify "bubbles" of radio emission that are extended ~10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the Teacup AGN hosts a compact radio structure, located ~0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v=-760 km/s. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~10...

  3. The complex optical to soft x-ray spectrum of the low-redshift radio-quiet quasars

    Science.gov (United States)

    Fiore, Fabrizio; Elvis, Martin; Mcdowell, Jonathan C.; Siemiginowska, Aneta; Wilkes, Belinda J.

    1994-01-01

    Eight high signal-to-noise ROSAT Position Sensitive Proportional Counter (PSPC) observations of six low-redshift (o.048 less than z less than 0.155) radio-quiet quasars have been analyzed to study ant soft excess. All the spectra can, at least roughly, be described int eh 0.1-2.5 keV band by simple power laws reduced at low energies by Galactic absorption. The strong oxygen edges seen in the PSPC spectra of several Seyfert galaxies and quasars are not observed in this sample. The limits implied for the abount of absorbing gas intrinsic to the quasars are particularly tight: of the order of approximately 10(exp 20)/sq cm. THe range of energy indices is broad: 1.3 less than alpha(sub E) less than 2.3. The energy indices are systematically steeper than those found in the same sources at higher energies (by DELTA alpha(sub E) approximately 0.5-1 with respect to Ginga or EXOSAT (2-10 keV) measurements, and by DELTA alpha(sub E) approximately 0.5 with respect to IPC (0.2-3.5 keV) measurements). This suggests a break between the hard and soft components in the keV region and, therefore, that the PSPC spectra are strongly dominated by the soft compnents. In fact, a fit tot he composite, high signal-to-noise spectrum reveals a significant excess above approximately 1 keV withrespect to the simple power-law model. No evidence for strong emission lines is found in any of the quasars. This argues against emission from an ionized plasma as the main contributor to the soft X-ray compnentunless there is a distribution of te mperatures. If the soft X-ray spectrum of thee quasars is dominated by radiation reflected by the photoinonized surface of an accretion disk, the absence of strong emissionlines suggests high ionization parameters and therefore high accretion rates. We include in two Appendices a comarison of the two official PSPC resolution matrices, those released on1992 March and on 1993 January, a discussion of the amplitude of the residual systematic uncertainties in 1993

  4. SDSS J0159+0105: A Radio-Quiet Quasar with a Centi-Parsec Supermassive Black Hole Binary Candidate

    Science.gov (United States)

    Zheng, Zhen-Ya; Butler, Nathaniel R.; Shen, Yue; Jiang, Linhua; Wang, Jun-Xian; Chen, Xian; Cuadra, Jorge

    2016-08-01

    We report a candidate centi-parsec supermassive black hole binary (SMBHB) in the radio-quiet quasar SDSS J0159+0105 at z = 0.217. With a modified Lomb–Scargle code (GLSdeDRW) and auto-correlation analysis, we detect two significant (at P > 99%) periodic signals at ˜741 day and ˜1500 day from the 8.1 yr Catalina V-band light curve of this quasar. The period ratio, which is close to 1:2, is typical of a black hole binary system with a mass ratio of 0.05 numerical simulations. SDSS J0159+0105 has two SDSS spectroscopic observations separated by ˜10 yr. There is a significant change in the broad Hβ profile between the two epochs, which can be explained by a single broad-line region (BLR) around the binary system illuminated by the aforementioned mini-disks, or a stream of gas flowing from the circumbinary disk to one of the SMBHs. From the single BLR assumption and the orbital period t orb ˜ 1500 day, we estimate the total virial masses of M SMBHB ˜ 1.3 × 108 M ⊙, the average distances of BLR of ˜0.04 pc (˜50 lt-day, with ±0.3 dex uncertainty), and an SMBHB separation of d = (0.01 pc){M}8,{tot}1/3 (T rest/3.3 yr)2/3 ˜ 0.013 pc (15 lt-day). Based on analytical work, the postulated circumbinary disk has an inner radius of 2d = 0.026 pc (30 lt-day). SDSS J0159+0105 also displays unusual spectral energy distribution. The unique properties of SDSS J0159+0105 are consistent with it being a centi-parsec SMBHB. This paper uses data from the Sloan Digital Sky Survey (SDSS), Catalina Real-time Transient Survey (CRTS), SWIFT, GALEX, 2MASS, and WISE archive.

  5. Storm in a "Teacup": A Radio-quiet Quasar with ≈10 kpc Radio-emitting Bubbles and Extreme Gas Kinematics

    Science.gov (United States)

    Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Bauer, F. E.; Edge, A. C.; Hogan, M. T.; Mullaney, J. R.; Swinbank, A. M.

    2015-02-01

    We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L 1.4 GHz ≈ 5 × 1023 W Hz-1 and L AGN ≈ 2 × 1045 erg s-1). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the "Teacup" active galactic nucleus (AGN) in the literature. We identify "bubbles" of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the "Teacup" AGN hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = -740 km s-1. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~ 10 kpc scales. Our study highlights that even when a quasar is formally "radio-quiet" the radio emission can be extremely effective for observing the effects of AGN feedback.

  6. STORM IN A {sup T}EACUP{sup :} A RADIO-QUIET QUASAR WITH ≈10 kpc RADIO-EMITTING BUBBLES AND EXTREME GAS KINEMATICS

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Edge, A. C.; Hogan, M. T.; Swinbank, A. M. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontifica Universidad Católica de Chile, 306, Santiago 22 (Chile); Mullaney, J. R., E-mail: c.m.harrison@mail.com [Department of Physics and Astronomy, University of Sheffield, Sheffield S7 3RH (United Kingdom)

    2015-02-10

    We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L {sub 1.4} {sub GHz} ≈ 5 × 10{sup 23} W Hz{sup –1} and L {sub AGN} ≈ 2 × 10{sup 45} erg s{sup –1}). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the ''Teacup'' active galactic nucleus (AGN) in the literature. We identify ''bubbles'' of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the ''Teacup'' AGN hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = –740 km s{sup –1}. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on ≳ 10 kpc scales. Our study highlights that even when a quasar is formally ''radio-quiet'' the radio emission can be extremely effective for observing the effects of AGN feedback.

  7. The transition from quasar radio-loud to radio-quiet state in the framework of the black hole scalability hypothesis

    CERN Document Server

    Marecki, Andrzej

    2010-01-01

    There are several lines of evidence that active galactic nuclei (AGN) can be regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary phenomena in these two classes are proportional to the black hole (BH) masses. Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to be followed directly. What could be done, however, is to assign particular types of active galaxies to different evolutionary stages observable in XRBs. We studied such an assignment for three quasars with clear signatures of a recent transition from the radio-loud to the radio-quiet state. The quasars we investigated have large-scale radio lobes that are clearly asymmetric -- one lobe is of Fanaroff-Riley II type, while the other one is a diffuse relic devoid of a hotspot. We suggest that the prime cause of the asymmetry of these radio sources is that the nuclei of their host galaxies currently produce no jets. To prove that, we observed them with milliarcsecond resolution to check if they are simila...

  8. An Accretion Disc-Irradiation Hybrid Model for The Optical/UV Variability in Radio-Quiet Quasars

    CERN Document Server

    Liu, Hui; Gu, Minfeng

    2016-01-01

    The optical/ultraviolet (UV) variability of quasars has been discovered to be correlated with other quasar properties, such as luminosity, black hole mass and rest-frame wavelength. However,the origin of variability has been a puzzle so far. In this work, we upgrade the accretion disc model (Li & Cao 2008), which assumed the variability is caused by the change of global mass accretion rate, by constraining the disc size to match the viscous timescale of accretion disc to the variability timescale observed and by including the irradiation/X-ray reprocessing to make the emitted spectrum become steeper. We find this hybrid model can reproduce the observed bluer-when-brighter trend quite well, which is used to validate the theoretical model by several works recently. The traditional correlation between the variability amplitude and rest-frame wavelength can also be well fitted by our model. In addition, a weak positive correlation between variability amplitude and black hole mass is present, qualitatively con...

  9. An accretion disc-irradiation hybrid model for the optical/UV variability in radio-quiet quasars

    Science.gov (United States)

    Liu, Hui; Li, Shuang-Liang; Gu, Minfeng; Guo, Hengxiao

    2016-10-01

    The optical/ultraviolet (UV) variability of quasars has been discovered to be correlated with other quasar properties, such as luminosity, black hole mass and rest-frame wavelength. However, the origin of variability has been a puzzle so far. In this work, we upgrade the accretion disc model, which assumed the variability is caused by the change of global mass accretion rate, by constraining the disc size to match the viscous time-scale of accretion disc to the variability time-scale observed and by including the irradiation/X-ray reprocessing to make the emitted spectrum become steeper. We find this hybrid model can reproduce the observed bluer-when-brighter trend quite well, which is used to validate the theoretical model by several works recently. The traditional correlation between the variability amplitude and rest-frame wavelength can also be well fitted by our model. In addition, a weak positive correlation between variability amplitude and black hole mass is present, qualitatively consistent with recent observations.

  10. Radio-quiet Fast Coronal Mass Ejections

    Science.gov (United States)

    Gopalswamy, N.; Aguilar-Rodriguez, E.; Kaiser, M. L.; Howard, R. A.

    2004-12-01

    Coronal mass ejections (CMEs) drive shocks in the interplanetary medium that produce type II radio emission. These CMEs are faster and wider on the average, than the general population of CMEs. However, when we start from fast (speed > 900 km/s) and wide (angular width > 60 degrees), more than half of them are not associated with radio bursts. In order to understand why these CMEs are radio quiet, we collected all the fast and wide (FW) CMEs detected by the Solar and Heliospheric Observatory (SOHO) mission's Large Angle and Spectrometric Coronagraph (LASCO) and isolated those without associated type II radio bursts. The radio bursts were identified in the dynamic spectra of the Radio and Plasma Wave (WAVES) Experiment on board the Wind spacecraft. We also checked the list against metric type II radio bursts reported in Solar Geophysical Data and isolated those without any radio emission. This exercise resulted in about 140 radio-quiet FW CMEs. We identified the source regions of these CMEs using the Solar Geophysical Data listings, cross-checked against the eruption regions in the SOHO/EIT movies. We explored a number of possibilities for the radio-quietness: (i) Source region being too far behind the limb, (ii) flare size, (iii) brightness of the CME, and (iv) the density of the ambient medium. We suggest that a combination of CME energy and the Alfven speed profile of the ambient medium is primarily responsible for the radio-quietness of these FW CMEs.

  11. Width of Radio-Loud and Radio-Quiet CMEs

    OpenAIRE

    Michalek, G.; Gopalswamy, N.; Xie, H.

    2007-01-01

    In the present paper we report on the difference in angular sizes between radio-loud and radio-quiet CMEs. For this purpose we compiled these two samples of events using Wind/WAVES and SOHO/LASCO observations obtained during 1996-2005. It is shown that the radio-loud CMEs are almost two times wider than the radio-quiet CMEs (considering expanding parts of CMEs). Furthermore we show that the radio-quiet CMEs have a narrow expanding bright part with a large extended diffusive structure. These r...

  12. THE XMM-NEWTON X-RAY SPECTRA OF THE MOST X-RAY LUMINOUS RADIO-QUIET ROSAT BRIGHT SURVEY-QSOs: A REFERENCE SAMPLE FOR THE INTERPRETATION OF HIGH-REDSHIFT QSO SPECTRA

    International Nuclear Information System (INIS)

    We present the broadband X-ray properties of four of the most X-ray luminous (LX ≥ 1045 erg s-1 in the 0.5-2 keV band) radio-quiet QSOs found in the ROSAT Bright Survey. This uniform sample class, which explores the extreme end of the QSO luminosity function, exhibits surprisingly homogenous X-ray spectral properties: a soft excess with an extremely smooth shape containing no obvious discrete features, a hard power law above 2 keV, and a weak narrow/barely resolved Fe Kα fluorescence line for the three high signal-to-noise ratio (S/N) spectra. The soft excess can be well fitted with only a soft power law. No signatures of warm or cold intrinsic absorbers are found. The Fe Kα centroids and the line widths indicate emission from neutral Fe (E = 6.4 keV) originating from cold material from distances of only a few light days or further out. The well-constrained equivalent widths (EW) of the neutral Fe lines are higher than expected from the X-ray Baldwin effect which has been only poorly constrained at very high luminosities. Taking into account our individual EW measurements, we show that the X-ray Baldwin effect flattens above LX ∼ 1044 erg s-1 (2-10 keV band) where an almost constant (EW) of ∼100 eV is found. We confirm the assumption of having very similar X-ray active galactic nucleus properties when interpreting stacked X-ray spectra. Our stacked spectrum serves as a superb reference for the interpretation of low S/N spectra of radio-quiet QSOs with similar luminosities at higher redshifts routinely detected by XMM-Newton and Chandra surveys.

  13. Radio Loud and Radio Quiet Quasars

    CERN Document Server

    Kellermann, K I; Kimball, A E; Perley, R A; Ivezic, Zeljko

    2016-01-01

    We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low redshift ($0.2 5 \\mathrm{~mJy~beam}^{-1}$ ($log(L) \\gtrsim 24$). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio loud.

  14. Galaxies at Z=2 extensions around radio-quiet QSOs

    CERN Document Server

    Aretxaga, I; Terlevich, R J

    1995-01-01

    We have been conducting an imaging survey to detect host galaxies of radio-quiet QSOs at high redshift (z = 2), in order to compare them with those of radio-loud objects. Six QSOs were observed in the R passband with the auxiliary port of the 4.2m WHT of the {\\it Observatorio de Roque de los Muchachos} indir August 1994. The objects were selected to be bright (M(B) < -28~mag) and have bright stars in the field, which could enable us to define the point spread function (PSF) accurately. The excellent seeing of La Palma (<0.9 arcsec thoughout the run) allowed us to detect extensions to the nuclear PSFs around three (one radio-loud and two radio-quiet) QSOs, out of 4 suitable targets. The extensions are most likely due to the host galaxies of these QSOs, with luminosities of at least 3-7% of the QSO luminosity. The most likely values for the luminosity of the host galaxies lie in the range 6-18% of the QSO luminosity. Our observations show that, if the extensions we have detected are indeed galaxies, extra...

  15. Compact radio cores in radio-quiet AGNs

    CERN Document Server

    Maini, Alessandro; Norris, Ray P; Giovannini, Gabriele; Spitler, Lee R

    2016-01-01

    The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGN) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. We report on a first direct evidence of radio cores in RQ AGNs at cosmological reds...

  16. Are there Radio-quiet Solar Flares?

    CERN Document Server

    Benz, A O; Magdalenic, J; Benz, Arnold O.; Brajsa, Roman; Magdalenic, Jasmina

    2007-01-01

    Some 15% of solar flares having a soft X-ray flux above GOES class C5 are reported to lack coherent radio emission in the 100 - 4000 MHz range (type I - V and decimetric emissions). A detailed study of 29 such events reveals that 22 (76%) of them occurred at a radial distance of more than 800'' from the disk center, indicating that radio waves from the limb may be completely absorbed in some flares. The remaining seven events have statistically significant trends to be weak in GOES class and to have a softer non-thermal X-ray spectrum. All of the non-limb flares that were radio-quiet > 100 MHz were accompanied by metric type III emission below 100 MHz. Out of 201 hard X-ray flares, there was no flare except near the limb (R>800'') without coherent radio emission in the entire meter and decimeter range. We suggest that flares above GOES class C5 generally emit coherent radio waves when observed radially above the source.

  17. Intranight optical variability of radio-quiet BL Lacertae objects

    CERN Document Server

    Liu, Yuan; Zhang, Shuang Nan

    2015-01-01

    Aims: The intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight variation is helpful in distinguishing the mechanism of the continuum of radio-quiet BL Lac objects. Methods: We conducted a photometric monitoring of 8 radio-quiet BL Lac objects by Xinglong 2.16m and Lijiang 2.4m telescopes. The differential light curves are calculated between each target and two comparison stars. To qualify the variation, the significance of variation is examined by scaled $F$-test. Results: No significant variation is found in the 11 sessions of light curves of 8 radio-quiet BL Lac objects (one galactic source is excluded). The lack of microvariation in radio-quiet BL Lac objects is consistent with the detection rate of microvariation in normal radio-quiet AGNs, but much lower than that of radio-loud AGNs. This result indicates that the continua of t...

  18. Spectroscopy of bright quasars: emission lines and internal extinction

    CERN Document Server

    Bachev, R; Semkov, E; Mihov, B

    2008-01-01

    The main purpose of this work is to improve the existing knowledge about the most powerful engines in the Universe - quasars. Although a lot is already known, we still have only a vague idea how these engines work exactly, why they behave as they do, and what the relation is between their evolution and the evolution of their harboring galaxy. Methods we used are based on optical spectroscopy of visually bright quasars, many of which have recently been discovered as X-ray sources, but eventually missed in color-selected surveys. The spectra typically cover the 4200-7000 AA region, allowing measurements of the characteristics of the hydrogen lines, the FeII contribution, and other lines of interest. We present accurate redshift estimates and Seyfert type classification of the objects. We also show that the contribution of the host galaxy to the optical continuum is non-negligible in many cases, as is the intrinsic AGN absorption. Consequences of not correcting for those factors when estimating different quasar ...

  19. Seoul National University Bright Quasar Survey in Optical (SNUQSO) I: First Phase Observations and Results

    CERN Document Server

    Lee, Induk; Kim, Minjin; Kang, Eugene; Shim, Hyunjin; Richards, Gordon T; Edge, Alastair C; Lee, Myung Gyoon; Park, Changbom; Park, Myeong-Gu

    2008-01-01

    We present results from the first phase of the Seoul National University Bright Quasar Survey in Optical (SNUQSO) as well as its basic observational setup. Previous and current large-area surveys have been successful in identifying many quasars, but they could have missed bright quasars due to their survey design. In order to help complete the census of bright quasars, we have performed spectroscopic observations of new bright quasar candidates selected from various methods based on optical colors, near-infrared colors, radio, and X-ray data. In 2005/2006, we observed 55 bright quasar candidates using the Bohyunsan Optical Echelle Spectrograph (BOES) on the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory in Korea. We identify 14 quasars/Seyferts from our observation, including an optically bright quasar with i=14.98 mag at z=0.092 (SDSS J003236.59-091026.2). Non-quasar/Seyfert objects are found to be mostly stars, among which there are five M-type stars and one cataclysmic variable. Our result ...

  20. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    Science.gov (United States)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  1. Discovery of the optically bright, wide separation double quasar SDSS J1442+4055

    CERN Document Server

    Sergeyev, Alexey V; Shalyapin, Vyacheslav N; Goicoechea, Luis J

    2015-01-01

    Optically bright, wide separation double (gravitationally lensed) quasars can be easily monitored, leading to light curves of great importance in determining the Hubble constant and other cosmological parameters, as well as the structure of active nuclei and halos of galaxies. Searching for new double quasars in the SDSS-III database, we discovered SDSS J1442+4055. This consists of two bright images (18-19 magnitudes in the r band) of the same distant quasar at redshift z = 2.575. The two quasar images are separated by about 2.1 arcsec, show significant parallel flux variations and can be monitored from late 2015. We also found other two double quasar candidates, SDSS J1617+3827 (z = 2.079) and SDSS J1642+3200 (z = 2.264), displaying evidence for the presence of a lensing object and parallel flux variations, but requiring further spectroscopic observations to be confirmed as lensed quasars.

  2. Mass Functions of the Active Black Holes in Distant Quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the Color-Selected Sample of the SDSS Fall Equatorial Stripe

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Osmer, Patrick S.

    2009-01-01

    We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey, the Bright Quasar Survey, and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts (0...... functions at similar redshifts based on the SDSS Data Release 3 quasar catalog presented by Vestergaard et al. We see clear evidence of cosmic downsizing in the comoving space density distribution of active black holes in the LBQS sample alone. In forthcoming papers, further analysis, comparison......, and discussion of these mass functions will be made with other existing black hole mass functions, notably that based on the SDSS DR3 quasar catalog. We present the relationships used to estimate the black hole mass based on the MgII emission line; the relations are calibrated to the Hbeta and CIV relations...

  3. Radio Quiet Protection at the Australian Square Kilometre array site

    Science.gov (United States)

    Harvey-Smith, Lisa

    2015-08-01

    Radio astronomy relies on the detection of very faint signals from the universe. Many radio telescopes are now detrimentally affected by radio frequency interference (RFI), which results from a wide range of active spectrum users such as communications, aviation and satellites. This is why many new radio observatories are being sited at increasingly remote locations.The site for the Square Kilometre Array and its pathfinders in Australia is the Murchison Radio-Astronomy Observatory (MRO). The MRO is located more than 350km from the nearest population centre and has a large radio-quiet zone that is managed under a range of legislative agreements.In this talk I will describe the radio quiet zone, what protection it gives, how it works and how astronomers interact with the spectrum management authorities.

  4. The SDSS view of the Palomar-Green bright quasar survey

    Energy Technology Data Exchange (ETDEWEB)

    Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Vanden Berk, Daniel E.; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Smith, J.Allyn; Tucker, Douglas, L.; Yanny, Brian; /Fermilab /Penn State U., Astron. Astrophys. /Princeton U.

    2005-02-01

    The author investigates the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, they define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B < -0.71, implying a color-related incompleteness. As the color distribution of bright quasars peaks near U-B = -0.7 and the 2-{sigma} error in U-B is comparable to the full width of the color distribution of quasars, the color incompleteness of the BQS is approximately 50% and essentially random with respect to U-B color for z < 0.5. There is however, a bias against bright quasars at 0.5 < z < 1, which is induced by the color-redshift relation of quasars (although quasars at z > 0.5 are inherently rare in bright surveys in any case). They find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects which are blue in g-i, in particular compared to the full range of g-i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.

  5. Long-term Optical Variability of Radio-Selected Quasars from the FIRST Survey

    CERN Document Server

    Helfand, D J; Willman, B; White, R L; Becker, R H; Price, T; Gregg, M D; McMahon, R G; Helfand, David J.; Stone, Remington P.S.; Willman, Beth; White, Richard L.; Becker, Robert H.; Price, Trevor; Gregg, Michael D.; Mahon, Richard G. Mc

    2001-01-01

    We have obtained single-epoch optical photometry for 201 quasars, taken from the FIRST Bright Quasar Survey, which span a wide range in radio loudness. Comparison with the magnitudes of these objects on the POSS-I plates provides by far the largest sample of long-term variability amplitudes for radio-selected quasars yet produced. We find the quasars to be more variable in the blue than in the red band, consistent with work on optically selected samples. The previously noted trend of decreasing variability with increasing optical luminosity applies only to radio-quiet objects. Furthermore, we do not confirm a rise in variability amplitude with redshift, nor do we see any dependence on radio flux or luminosity. The variability over a radio-optical flux ratio range spanning a factor of 60,000 from radio-quiet to extreme radio-loud objects is largely constant, although there is a suggestion of greater variability in the extreme radio-loud objects. We demonstrate the importance of Malmquist bias in variability st...

  6. The SDSS View of the Palomar-Green Bright Quasar Survey

    CERN Document Server

    Jester, S; Richards, G T; Green, R F; Schmidt, M; Hall, P B; Strauss, M A; Vanden Berk, Daniel E; Stoughton, C; Gunn, J E; Brinkmann, J; Kent, S M; Smith, J A; Tucker, D L; Yanny, B; Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Berk, Daniel E. Vanden; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Tucker, Douglas L.; Yanny, Brian

    2005-01-01

    We investigate the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, we define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B 0.5 are inherently rare in bright surveys in any case). We find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects w...

  7. X-Ray and Multiwavelength Insights into the Nature of Weak Emission-line Quasars at Low Redshift

    Science.gov (United States)

    Wu, Jianfeng; Brandt, W. N.; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Hall, Patrick B.; Plotkin, Richard M.; Schneider, Donald P.; Shemmer, Ohad

    2012-03-01

    We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of >~ 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization "shielding gas" covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our X

  8. Radio Quiet Zones (RQZ) - Working with national communication administrations

    Science.gov (United States)

    Tzioumis, Anastasios

    Radio Astronomy detects extremely faint radio signals from space, and hence is very susceptible to Radio Frequency Interference (RFI) from other radio communication services. Although radio astronomy has been allocated some radio bands by the International Telecommunications Union (ITU), cosmic radio emissions occur over the whole of the electromagnetic spectrum. Thus, there is a need for radio telescopes to operate over very wide radio bands and avoid RFI. Radio Quiet Zones (RQZ) in various forms have been implemented around many radio astronomy observatories, to minimise the impact of RFI on radio astronomy observations by coordinating with nearby radiocommunication services. The history and characteristics of such RQZ around the world will be reviewed, with emphasis on recent experience. For the next generation radio astronomy telescopes such as the Square Kilometre Array (SKA), it will be of critical importance to minimise RFI over the whole operating frequency range 200 MHz - 25 GHz. Progress towards establishing strict RQZ for the SKA will be reviewed. The main experience and lesson learned is that it is critical to work closely with national communication administrations. Work on RQZ in international bodies and the implications for radio sciences will also be discussed.

  9. Local area networking in a radio quiet environment

    Science.gov (United States)

    Childers, Edwin L.; Hunt, Gareth; Brandt, Joseph J.

    2002-11-01

    The Green Bank facility of the National Radio Astronomy Observatory is spread out over 2,700 acres in the Allegheny Mountains of West Virginia. Good communication has always been needed between the radio telescopes and the control buildings. The National Radio Quiet Zone helps protect the Green Bank site from radio transmissions that interfere with the astronomical signals. Due to stringent Radio Frequency Interference (RFI) requirements, a fiber optic communication system was used for Ethernet transmissions on the site and coaxial cable within the buildings. With the need for higher speed communications, the entire network has been upgraded to use optical fiber with modern Ethernet switches. As with most modern equipment, the implementation of the control of the newly deployed Green Bank Telescope (GBT) depends heavily on TCP/IP. In order to protect the GBT from the commodity Internet, the GBT uses a non-routable network. Communication between the control building Local Area Network (LAN) and the GBT is implemented using a Virtual LAN (VLAN). This configuration will be extended to achieve isolation between trusted local user systems, the GBT, and other Internet users. Legitimate access to the site, for example by remote observers, is likely to be implemented using a virtual private network (VPN).

  10. Intra-night Optical Variability of Luminous Radio Quiet QSOs

    CERN Document Server

    Gupta, A C

    2005-01-01

    In the present paper we report the detection of intra-night variability in some of the RQQSOs and one LDQ. To study intra-night variability, we carried out photometric monitoring of seven RQQSOs and one LDQ in Johnson V-passband using 1.2 meter optical/IR telescope at Gurushikhar, Mount Abu, India. Observations were made in nine nights during the first half of the year 2000; seven RQQSOs: 0748+291, 0945+438, 1017+280, 1029+329, 1101+319, 1225+317, 1252+020 and one LDQ: 1103-006 were observed. RQQSOs 0748+291, 1225+317 and LDQ 1103-006 have shown existence of intra-night variations. In the case of 1017+280 (RQQSO) there is indication of intra-night variation in one night where as the observations in another night do not show convincingly the existence of intra-night variability. RQQSOs 0945+438, 1029+329, 1101+319 and 1252+020 have not shown any intra-night variations. We compiled intra-night variability data for radio-loud and radio-quiet AGNs from the literature for statistical analysis. It is found that a g...

  11. Isotropic AGN Heating with Small Radio Quiet Bubbles in the NGC 5044 Group

    CERN Document Server

    David, L; Giacintucci, S; Forman, W; Nulsen, P; Vrtilek, J; O'Sullivan, E; Raychaudhuri, S

    2009-01-01

    (Abridged) A Chandra observation of the X-ray bright group NGC 5044 shows that the X-ray emitting gas has been strongly perturbed by recent outbursts from the central AGN and also from motion of the central dominant galaxy relative to the group gas. The NGC 5044 group hosts many small radio quiet cavities with a nearly isotropic distribution, cool filaments, a semi-circular cold front and a two-armed spiral shaped feature of cool gas. A GMRT observation of NGC 5044 at 610 MHz shows the presence of extended radio emission with a "torus-shaped" morphology. The largest X-ray filament appears to thread the radio torus, suggesting that the lower entropy gas within the filament is material being uplifted from the center of the group. The radio emission at 235 MHz is much more extended than the emission at 610 MHz, with little overlap between the two frequencies. One component of the 235 MHz emission passes through the largest X-ray cavity and is then deflected just behind the cold front. A second detatched radio lo...

  12. The New Generation Atlas of Quasar Spectral Energy Distributions from Radio to X-rays

    CERN Document Server

    Shang, Zhaohui; Wills, Beverley J; Wills, Derek; Cales, Sabrina; Dale, Daniel A; Green, Richard F; Runnoe, Jessie; Nemmen, Rodrigo S; Gallagher, Sarah; Ganguly, Rajib; Hines, Dean C; Kelly, Benjamin; Kriss, Gerard A; Li, Jun; Tang, Baitian; Xie, Yanxia

    2011-01-01

    We have produced the next generation of quasar spectral energy distributions (SEDs), essentially updating the work of Elvis et al. (1994) by using high-quality data obtained with several space and ground-based telescopes, including NASA's Great Observatories. We present an atlas of SEDs of 85 optically bright, non-blazar quasars over the electromagnetic spectrum from radio to X-rays. The heterogeneous sample includes 27 radio-quiet and 58 radio-loud quasars. Most objects have quasi-simultaneous ultraviolet-optical spectroscopic data, supplemented with some far-ultraviolet spectra, and more than half also have Spitzer mid-infrared IRS spectra. The X-ray spectral parameters are collected from the literature where available. The radio, far-infrared, and near-infrared photometric data are also obtained from either the literature or new observations. We construct composite spectral energy distributions for radio-loud and radio-quiet objects and compare these to those of Elvis et al., finding that ours have similar...

  13. QUASARS PROBING QUASARS. IV. JOINT CONSTRAINTS ON THE CIRCUMGALACTIC MEDIUM FROM ABSORPTION AND EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Hennawi, Joseph F.; Prochaska, J. Xavier, E-mail: xavier@ucolick.org [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

    2013-03-20

    We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantly radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar-powered fluorescence

  14. RADIOASTRON OBSERVATIONS OF THE QUASAR 3C273: A CHALLENGE TO THE BRIGHTNESS TEMPERATURE LIMIT

    Energy Technology Data Exchange (ETDEWEB)

    Kovalev, Y. Y.; Kardashev, N. S.; Voitsik, P. A.; Kovalev, Yu. A.; Lisakov, M. M.; Sokolovsky, K. V. [Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation); Kellermann, K. I. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Lobanov, A. P.; Zensus, J. A.; Anderson, J. M.; Bach, U.; Kraus, A. [Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 (Germany); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gurvits, L. I. [Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Jauncey, D. L. [CSIRO Astronomy and Space Sciences, Epping, NSW 1710 (Australia); Ghigo, F. [National Radio Astronomy Observatory, Rt. 28/92, Green Bank, WV 24944-0002 (United States); Ghosh, T.; Salter, C. J. [Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo, Puerto Rico, PR 00612 (United States); Petrov, L. Yu. [Astrogeo Center, 7312 Sportsman Drive, Falls Church, VA 22043 (United States); Romney, J. D. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States)

    2016-03-20

    Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of 10{sup 11.5} K. Relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 10{sup 13} K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as small as 26 μas (2.7 light months) and brightness temperature in excess of 10{sup 13} K. These measurements challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive black holes and require a much higher Doppler factor than what is determined from jet apparent kinematics.

  15. A survey of luminous high-redshift quasars with SDSS and WISE II. the bright end of the quasar luminosity function at z ~ 5

    CERN Document Server

    Yang, Jinyi; Wu, Xue-Bing; Fan, Xiaohui; McGreer, Ian D; Bian, Fuyan; Yi, Weimin; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Green, Richard; Jiang, Linhua; Wang, Shu; Wang, Ran; Yue, Minghao

    2016-01-01

    This is the second paper in a series on a new luminous z ~ 5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z ~ 5. Combined our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z ~ 5 quasar sample to date, with 99 quasars in the range 4.7 <= z < 5.4 and -29 < M1450 <= -26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/Va method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as alpha = -2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope beta = -3.58+/-0.24 and a fainter break magnitude M*1450 = -26.98+/-0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a lum...

  16. Combined X-Ray and mm-Wave Observations of Radio Quiet Active Galaxies

    Science.gov (United States)

    Behar, E.

    2016-06-01

    A connection between the X-ray and radio sources in radio quiet active galaxies (AGNs) will be demonstrated. High radio frequency, i.e., mm-wave observations are promising probes of the X-ray emitting inner regions of the accretion disks in radio quiet AGNs. An argument for simultaneous observations in X-rays and in mm waves will be made, in order to promote these as one of the future science goals of X-ray and AGN astronomy in the next decade. Preliminary results from an exploratory campaign with several space and ground based telescopes will be presented.

  17. An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?

    CERN Document Server

    Xie, Xiaoyi; Shao, Zhengyi; Yin, Jun

    2015-01-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., $\\alpha_{\

  18. The apparently normal galaxy hosts for two luminous quasars

    CERN Document Server

    Bahcall, J N; Bahcall, John N; Schneider, Donald P

    1995-01-01

    HST images (with WFPC2) of PHL~909\\ (z = 0.171) and PG~0052+251\\ (z = 0.155) show that these luminous radio-quiet quasars each occur in an apparently normal host galaxy. The host galaxy of PHL~909 is an elliptical galaxy (\\sim E4) and the host of PG~0052+251 is a spiral (\\sim~Sb). Both host galaxies are several tenths of a magnitude brighter than L^*, the characteristic Schechter luminosity of field galaxies. The images of PHL~909 and PG~0052+251, when compared with HST images of other objects in our sample of 20 luminous, small-redshift (z \\leq 0.30) quasars, show that luminous quasars occur in a variety of environments. The local environments of the luminous quasars range from luminous ellipticals, to apparently normal host galaxies, to complex systems of interacting components, to faint (and as yet undetected) hosts. The bright HII regions of the host galaxy of PG~0052+251 provide an opportunity to measure directly the metallicity of the host of a luminous quasar, to establish an upper limit to the mass of...

  19. Subaru high-$z$ exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at $5.7 < z < 6.9$

    CERN Document Server

    Matsuoka, Yoshiki; Kashikawa, Nobunari; Iwasawa, Kazushi; Strauss, Michael A; Nagao, Tohru; Imanishi, Masatoshi; Niida, Mana; Toba, Yoshiki; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Foucaud, Sébastien; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E; Harikane, Yuichi; Ikeda, Hiroyuki; Kawaguchi, Toshihiro; Kikuta, Satoshi; Komiyama, Yutaka; Lupton, Robert H; Minezaki, Takeo; Miyazaki, Satoshi; Morokuma, Tomoki; Murayama, Hitoshi; Nishizawa, Atsushi J; Ono, Yoshiaki; Ouchi, Masami; Price, Paul A; Sameshima, Hiroaki; Silverman, John D; Sugiyama, Naoshi; Tait, Philip J; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Tang, Ji-Jia; Utsumi, Yousuke

    2016-01-01

    We report the discovery of 15 quasars and bright galaxies at $5.7 < z < 6.9$. This is the initial result from the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the exquisite multi-band imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg$^2$ of the survey footprint. The success rate of our photometric selection is quite high, approaching 100 % at the brighter magnitudes ($z_{\\rm AB} < 23.5$ mag). Our selection also recovered all the known high-$z$ quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-br...

  20. The XMM-Newton Bright Survey sample of absorbed quasars: X-ray and accretion properties

    CERN Document Server

    Ballo, L; Della Ceca, R; Caccianiga, A; Vignali, C; Carrera, F J; Corral, A; Mateos, S

    2014-01-01

    Although absorbed quasars are extremely important for our understanding of the energetics of the Universe, the main physical parameters of their central engines are still poorly known. In this work we present and study a complete sample of 14 quasars (QSOs) that are absorbed in the X-rays (column density NH>4x10^21 cm-2 and X-ray luminosity L(2-10 keV)>10^44 ergs/s; XQSO2) belonging to the XMM-Newton Bright Serendipitous Survey (XBS). From the analysis of their ultraviolet-to-mid-infrared spectral energy distribution we can separate the nuclear emission from the host galaxy contribution, obtaining a measurement of the fundamental nuclear parameters, like the mass of the central supermassive black hole and the value of Eddington ratio, lambda_Edd. Comparing the properties of XQSO2s with those previously obtained for the X-ray unabsorbed QSOs in the XBS, we do not find any evidence that the two samples are drawn from different populations. In particular, the two samples span the same range in Eddington ratios, ...

  1. Rapid infrared and optical variability in the bright quasar 3C273

    Energy Technology Data Exchange (ETDEWEB)

    Courvoisier, T.J.-L.; Robson, E.I.; Hughes, D.H.; Blecha, A.; Bouchet, P.; Schwarz, H.E.; Krisciunas, K.

    1988-09-22

    We have observed variations by a factor of two in the infrared flux from the bright quasar 3C273 on a timescale as short as one day. In February 1988, the behaviour of the source changed from having a stable infrared flux and slow optical variations to a state characterized by recurrent infrared and optical flaring. The optical variations were of several per cent per day, changing from increase to decrease approximately every week. The amplitude of the repeated optical flares was 30-40%. The data are consistent with re-injection/acceleration of electrons followed by rapid cooling. The inferred magnetic field is 0.7 gauss and the data are marginally consistent with no relativistic beaming.

  2. The very first Pop III stars and their relation to bright z~6 quasars

    CERN Document Server

    Trenti, M

    2007-01-01

    We discuss the link between dark matter halos hosting the first PopIII stars formed at redshift z > 40 and the rare, massive, halos that are generally considered to host bright z~6 quasars. We show that within the typical volume occupied by one bright high-z QSO the remnants of the first several thousands PopIII stars formed do not end up in the most massive halos at z~6, but rather live in a large variety of environments. The black hole seeds planted by these very first PopIII stars can easily grow to M > 10^{9.5} Msun by z=6 assuming Eddington accretion with radiative efficiency epsilon~0.1. Therefore quenching of the accretion is crucial to avoid an overabundance of supermassive black holes. We implement a simple feedback model for the growth of the seeds planted by PopIII stars and obtain a z~6 BH mass function consistent with the observed QSO luminosity function.

  3. Ubiquitous Giant Lyα Nebulae around the Brightest Quasars at z ∼ 3.5 Revealed with MUSE

    Science.gov (United States)

    Borisova, Elena; Cantalupo, Sebastiano; Lilly, Simon J.; Marino, Raffaella A.; Gallego, Sofia G.; Bacon, Roland; Blaizot, Jeremy; Bouché, Nicolas; Brinchmann, Jarle; Carollo, C. Marcella; Caruana, Joseph; Finley, Hayley; Herenz, Edmund C.; Richard, Johan; Schaye, Joop; Straka, Lorrie A.; Turner, Monica L.; Urrutia, Tanya; Verhamme, Anne; Wisotzki, Lutz

    2016-11-01

    Direct Lyα imaging of intergalactic gas at z∼ 2 has recently revealed giant cosmological structures around quasars, e.g., the Slug Nebula. Despite their high luminosity, the detection rate of such systems in narrow-band and spectroscopic surveys is less than 10%, possibly encoding crucial information on the distribution of gas around quasars and the quasar emission properties. In this study, we use the MUSE integral-field instrument to perform a blind survey for giant {Ly}α nebulae around 17 bright radio-quiet quasars at 3\\lt z\\lt 4 that does not suffer from most of the limitations of previous surveys. After data reduction and analysis performed with specifically developed tools, we found that each quasar is surrounded by giant {Ly}α nebulae with projected sizes larger than 100 physical kiloparsecs and, in some cases, extending up to 320 kpc. The circularly averaged surface brightness profiles of the nebulae appear to be very similar to each other despite their different morphologies and are consistent with power laws with slopes ≈ -1.8. The similarity between the properties of all these nebulae and the Slug Nebula suggests a similar origin for all systems and that a large fraction of gas around bright quasars could be in a relatively “cold” (T ∼ 104 K) and dense phase. In addition, our results imply that such gas is ubiquitous within at least 50 kpc from bright quasars at 3\\lt z\\lt 4 independently of the quasar emission opening angle, or extending up to 200 kpc for quasar isotropic emission. Based on observations made with ESO Telescopes at the Paranal Observatory under programs 094.A-0396, 095.A-0708, 096.A-0345, 094.A-0131, 095.A-0200, and 096.A-0222.

  4. Using radioactivities to improve the search for nearby radio-quiet neutron stars

    CERN Document Server

    Hohle, Markus M; Tetzlaff, Nina

    2008-01-01

    Neutron stars (NS) and black holes (BH) are sources of gravitational waves (GW) and the investigation of young isolated radio-quiet NS can in principle lead to constraints of the equation of state (EoS). The GW signal of merging NSs critically depends on the EoS. However, unlike radio pulsars young isolated radio-quiet neutron stars are hard to detect and only seven of them are known so far. Furthermore, for GW projects it is necessary to confine regions in the sky where and of which quantity sources of GW can be expected. We suggest strategies for the search for young isolated radio-quiet NSs. One of the strategies is to look for radioactivities which are formed during a supernova (SN) event and are detectable due to their decay. Radioactivities with half lives of ~1 Myr can indicate such an event while other remnants like nebulae only remain observable for a few kyrs. Here we give a brief overview of our strategies and discuss advantages and disadvantages

  5. The optical-UV emissivity of quasars: dependence on black hole mass and radio loudness

    CERN Document Server

    Shankar, Francesco; Knigge, Christian; Matthews, James; Buckland, Rachel; Hryniewicz, Krzysztof; Sivakoff, Gregory; Dai, Xinyu; Richardson, Kayleigh; Riley, Jack; Gray, James; La Franca, Fabio; Altamirano, Diego; Croston, Judith; Gandhi, Poshak; Hoenig, Sebastian F; McHardy, Ian; Middleton, Matthew

    2016-01-01

    We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 < z < 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) alpha_3000 continuum slopes (L_\

  6. BeppoSAX observations of quasars

    Energy Technology Data Exchange (ETDEWEB)

    Fiore, F.; Mineo, T.; Laor, A.; Giallongo, E

    1999-01-01

    We present results from recent BeppoSAX observations of low redshift (z<0.4, PG sample) and high redshift (2radio-quiet and radio-loud quasars. Significant curvature has been detected in the spectra of the observed PGs: the spectrum flattens by 0.5 above 2 keV. The possible presence of narrow features in the MECS spectra is discussed. Intrinsic absorption has been measured in the z=3.9 radio-loud quasar 1745+624. The z=2.3 radio-quiet quasar HE1104-1805 has been found at a very low flux level, in comparison with previous ROSAT and ASCA observations, implying large (factor of {approx} 4) variability on years timescales.

  7. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    CERN Document Server

    Nagai, H; Paladino, R; Hull, C L H; Cortes, P; Moellenbrock, G; Fomalont, E; Asada, K; Hada, K

    2016-01-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C~286 made with the ALMA at 1.3~mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south-west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17\\%, this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or EVPA) in the core is $\\sim$\\,$39^{\\circ}$, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report ...

  8. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    Science.gov (United States)

    Nagai, H.; Nakanishi, K.; Paladino, R.; Hull, C. L. H.; Cortes, P.; Moellenbrock, G.; Fomalont, E.; Asada, K.; Hada, K.

    2016-06-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C 286 made with the Atacama Large Millimeter and Submillimeter Array (ALMA) at 1.3 mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south–west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17%; this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or electric vector position angle (EVPA)) in the core is ˜39◦, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report a serendipitous detection of a sub-mJy source in the field of view, which is likely to be a submillimeter galaxy.

  9. Radio Luminosity,Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

    Institute of Scientific and Technical Information of China (English)

    Wei-Hao Bian; Yan-Mei Chen; Chen Hu; Kai Huang; Yan Xu

    2008-01-01

    We investigate the MBH-O'.relation for radio-loud quasars with redshift z<0.83 in Data Release 3 of the Sloan Digital Sky Survey (SDSS).The sample consists of 3772 quasars with better models of the H/~ and [O III] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass (MBH) is calculated from the broad H/line,and the host stellar velocity dispersion (σ*) is traced by the core [O III] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-O".relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ.relation than do the radio-quiet quasars.This deviation is only partly due to a possible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radioluminosity is proportional to M128+0.23-0.16 BH(LBol/LEdd)1.29+0.31-0.24 for radio-quiet quasars and to M3.10+0.6.-0.70(LBol.LEdd)4.18+1.40-1.10 for radio-loud quasars.The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.

  10. Spitzer observations of a gravitationally lensed quasar, QSO 2237+0305

    CERN Document Server

    Agol, Eric; Gorjian, Varoujan; Kimball, Amy; 10.1088/0004-637X/697/2/1010

    2009-01-01

    The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides a test of quasar models. Toward this end, we present Spitzer Space Telescope Infrared Spectrograph and Infrared Array Camera (IRAC) observations of QSO 2237+0305, finding the following. (1) The infrared (IR) spectral energy distribution (SED) is similar to that of other bright radio-quiet quasars, contrary to an earlier claim. (2) A dusty torus model with a small opening angle fits the overall shape of the IR SED well, but the quantitative agreement is poor due to an offset in wavelength of the silicate feature. (3) The flux ratios of the four lensed images can be derived from the IRAC data despite being unresolved. We find that the near-IR fluxes are increasingly affected by microlensing toward shorter wavelengths. (4) The wavelength dependence of the IRAC flux ratios is ...

  11. Cosmic Ray Spallation in Radio-Quiet Active Galactic Nuclei: A Case Study of NGC 4051

    CERN Document Server

    Turner, T J

    2009-01-01

    We investigate conditions for and consequences of spallation in radio-quiet Seyfert galaxies. The work is motivated by the recent discovery of significant line emission at 5.44 keV in Suzaku data from NGC 4051. The energy of the new line suggests an identification as Cr I Ka emission, however the line is much stronger than would be expected from material with cosmic abundances, leading to a suggestion of enhancement owing to nuclear spallation of Fe by low energy cosmic rays from the active nucleus. We find that the highest abundance enhancements are likely to take place in gas out of the plane of the accretion disk and that timescales for spallation could be as short as a few years. The suggestion of a strong nuclear flux of cosmic rays in a radio-quiet Seyfert galaxy is of particular interest in light of the recent suggestion from Pierre Auger Observatory data that ultra-high-energy cosmic rays may originate in such sources.

  12. The Hard X-ray Spectral Slope as an Accretion-Rate Indicator in Radio-Quiet Active Galactic Nuclei

    OpenAIRE

    Shemmer, Ohad; Brandt, W. N.; Netzer, Hagai; Maiolino, Roberto; Kaspi, Shai

    2006-01-01

    We present new XMM-Newton observations of two luminous and high accretion-rate radio-quiet active galactic nuclei (AGNs) at z~2. Together with archival X-ray and rest-frame optical spectra of three sources with similar properties as well as 25 moderate-luminosity radio-quiet AGNs at z~2 keV) X-ray power-law photon index on the broad H_beta emission-line width and on the accretion rate across ~3 orders of magnitude in AGN luminosity. Provided the accretion rates of the five luminous sources ca...

  13. Correlations between Optical Variability and Physical Parameters of Quasars

    Indian Academy of Sciences (India)

    Wenwen Zuo; Xue-Bing Wu; Yi-Qing Liu; Cheng-Liang Jiao

    2014-09-01

    Optical variability is an important feature of quasars. Taking advantage of a larger sample of 7658 quasars from SDSS Stripe 82 and relatively more photometric data points for each quasar, we estimate their variability amplitudes and divide the sample into small bins of various parameters. An anticorrelation between variability amplitude and rest-frame wavelength is found. Variability increases as either luminosity or Eddington ratio decreases. The relationship between variability and black hole mass is uncertain. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. With the Shakura–Sunyaev disk model, we find that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model. The different mechanisms in radio-loud and radio-quiet quasars are discussed.

  14. Blind search for radio-quiet and radio-loud gamma-ray pulsars with Fermi-LAT data

    CERN Document Server

    Rubtsov, G I

    2014-01-01

    The Fermi Large Area Telescope (LAT) has observed more than a hundred of gamma-ray pulsars, about one third of which are radio-quiet, i.e. not detected at radio frequencies. The most of radio-loud pulsars are detected by Fermi LAT by using the radio timing models, while the radio-quiet ones are discovered in a blind search. The difference in the techniques introduces an observational selection bias and, consequently, the direct comparison of populations is complicated. In order to produce an unbiased sample, we perform a blind search of gamma-ray pulsations using Fermi-LAT data alone. No radio data or observations at optical or X-ray frequencies are involved in the search process. We produce a gamma-ray selected catalog of 25 non-recycled gamma-ray pulsars found in a blind search, including 16 radio-quiet and 9 radio-loud pulsars. This results in the direct measurement of the fraction of radio-quiet pulsars $\\varepsilon_{RQ} = 64\\pm 10\\%$, which is in agreement with the existing estimates from the population ...

  15. Weak hard X-ray emission from two broad absorption line quasars observed with NuSTAR: Compton-thick absorption or intrinsic X-ray weakness?

    DEFF Research Database (Denmark)

    Luo, B.; Brandt, W. N.; Alexander, D. M.;

    2013-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus...

  16. The Contribution from Scattered Light to Quasar Galaxy Hosts

    CERN Document Server

    Young, S; Robinson, A; Capetti, A

    2009-01-01

    We present models representing the scattering of quasar radiation off free electrons and dust grains in geometries that approximate the structure of quasar host galaxies. We show that, for reasonable assumptions, scattering alone can easily produce ratios of nuclear (point source) to extended fluxes comparable to those determined in studies of quasar hosts. This result suggests that scattered quasar light, as well as stellar emission from the host galaxy, contributes significantly to the detected extended flux, leading to uncertainty in the inferred properties of quasar host. A significant contribution from scattered quasar light will lead to overestimates of the luminosity and hence mass of the host galaxy, and may also distort its morphology. Scattering of quasar light within the host galaxy may provide alternative explanations for the apparent peak in host luminosity at z = 2-3; possibly the overall average higher luminosity of radio-loud host galaxies relative to those of radio-quiet quasars (RQQs), and t...

  17. NASA gateways at L1 and L2 and the radio-quiet Moon Farside imperative

    Science.gov (United States)

    Maccone, Claudio

    2005-07-01

    NASA is currently studying the possibility of establishing future space bases at either of the libration points (also called Lagrangian points) L1 and L2 of the Earth Moon system. Two more similar points L1 and L2 of the Sun Earth system are also under consideration. Such possible future space bases are called Gateways in the NASA jargon. Each Gateway has its own pros and cons in terms of gravitational pull, distance from the Earth, and targets attainable by future spacecraft departing from the Gateway. A preliminary, concise review of these alternative possibilities is presented in this paper. We claim, however, that an extra factor has to be included in the NASA scenario also. This is the Radio-Quiet Moon Farside Imperative, called simply the Farside Imperative hereafter. This imperative is the need to keep at least the central part of the Farside of the Moon free from Radio Frequency Interference (RFI) coming from the Earth and shielded by the Moon's spherical body. In fact, the Farside of the Moon, and the Quiet Cone that extends into space above it for a few thousands of kilometers, represent a unique outpost for humankind: they are the only place close to the Earth where all radio-garbage produced by modern human civilization cannot reach. Thus, an array of radio antennas located there would sense the rest of the universe to an unprecedented degree of radio cleanliness, and, hence, of radio details. Not only would astrophysics and radio astronomy in general greatly benefit from this radio-quiet environment, but we would possibly achieve there for the first time a neat radio contact with an extraterrestrial civilization harboring somewhere else in the Galaxy (SETI) that could be too noisy to be detected on Earth. It is thus felt that a fair balance has to be reached between the astronautical drive to enlarge the exploration of the solar system and the imperative to keep the Farside of the Moon radio-clean. This paper puts forward a set of constructing

  18. VizieR Online Data Catalog: The UV-bright Quasar Survey (UVQS) DR1 (Monroe+, 2016)

    Science.gov (United States)

    Monroe, T. R.; Prochaska, J. X.; Tejos, N.; Worseck, G.; Hennawi, J. F.; Schmidt, T.; Tumlinson, J.; Shen, Y.

    2016-09-01

    We have performed an all-sky survey for z~1, FUV-bright quasars selected from GALEX and WISE photometry. We generated a list of 1450 primary candidates (Table1). In several of the observing runs, conditions were unexpectedly favorable and we exhausted the primary candidates at certain right ascension ranges. To fill the remaining observing time, we generated a secondary candidate list. This secondary set of candidates is provided in Table2. We proceeded to obtain discovery-quality longslit spectra (i.e., low-dispersion, large wavelength coverage, modest signal-to-noise ratio (S/N) of our UV-bright Quasar Survey (UVQS) candidates in one calendar year. Our principal facilities were: (i) the dual Kast spectrometer on the 3m Shane telescope at the Lick Observatory; (ii) the Boller & Chivens (BCS) spectrometer on the Irenee du Pont 100'' telescope at the Las Campanas Observatory; and (iii) the Calar Alto Faint Object Spectrograph on the CAHA 2.2m telescope at the Calar Alto Observatory (CAHA). We acquired an additional ~20 spectra on larger aperture telescopes (Keck/ESI, MMT/MBC, Magellan/MagE) during twilight or under poor observing conditions. Typical exposure times were limited to <~200s, with adjustments for fainter sources or sub-optimal observing conditions. Table3 provides a list of the observed candidates. There are 93 sources with a good quality spectrum for which we cannot recover a secure redshift. The majority of these have been previously cataloged as blazars (or BL Lac objects). Table6 lists the sample of these unknowns. (6 data files).

  19. XMM-Newton observations of 4 luminous radio-quiet AGN, and the soft X-ray excess problem

    CERN Document Server

    D'Ammando, F; Jimenez-Bailon, E; Matt, G

    2008-01-01

    The nature and origin of the soft X-ray excess in radio quiet AGN is still an open issue. The interpretation in terms of thermal disc emission has been challanged by the discovery of the constancy of the effective temperature despite the wide range of Black Hole masses of the observed sources. Alternative models are reflection from ionized matter and absorption in a relativistically smeared wind. We analyzed XMM-Newton observations of four luminous radio quiet AGN with the aim of characterising their main properties and in particular the soft excess. Different spectral models for the soft excess were tried: thermal disc emission, Comptonization, ionized reflection, relativistically smeared winds. Comptonization of thermal emission and the smeared winds provide the best fits, but the other models also provide acceptable fits. All models, however, return parameters very similar from source to source, despite the large differences in luminosities, Black Hole masses and Eddington ratios. Moreover, the smeared win...

  20. The Braking Index of Radio-quiet Gamma-ray Pulsar

    CERN Document Server

    Clark, C J; Wu, J; Guillemot, L; Camilo, F; Johnson, T J; Kerr, M; Allen, B; Aulbert, C; Beer, C; Bock, O; Cuéllar, A; Eggenstein, H B; Fehrmann, H; Kramer, M; Machenschalk, B; Nieder, L

    2016-01-01

    We report the discovery and timing measurements of PSR J1208-6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home. No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit at 1369 MHz of 30 $\\mu$Jy. By timing this pulsar's gamma-ray pulsations, we measure its braking index over five years of LAT observations to be $n = 2.598 \\pm 0.001 \\pm 0.1$, where the first uncertainty is statistical and the second estimates the bias due to timing noise. Assuming its braking index has been similar since birth, the pulsar has an estimated age of around 2,700 yr, making it the youngest pulsar to be found in a blind search of gamma-ray data and the youngest known radio-quiet gamma-ray pulsar. Despite its you...

  1. Evidence for ultra-fast outflows in radio-quiet AGNs: III - location and energetics

    CERN Document Server

    Tombesi, F; Reeves, J N; Braito, V

    2012-01-01

    Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultra-fast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval ~0.0003-0.03pc (~10^2-10^4 r_s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between ~0.01-1 M_{\\odot} yr^{-1}, corresponding to >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are log\\dot{E}_K~42.6-44.6 erg s^{-1}. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs ...

  2. The average x-ray/$\\gamma$-ray spectrum of radio-quiet Seyfert 1s

    CERN Document Server

    Gondek-Rosinska, D; Johnson, W N; George, I M; McNaron-Brown, K; Magdziarz, P; Smith, D; Gruber, E

    1996-01-01

    We have obtained the average 1--500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO, and GRO/OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well-fitted by a power-law X-ray continuum with an energy spectral index of \\alpha \\simeq 0.9 moderately absorbed by an ionized medium and with a Compton reflection component. A high-energy cutoff (or a break) in the the power-law component at a few hundred keV or more is required by the data. We also show that the corresponding average spectrum from HEAO A1 and A4 is fully compatible with that obtained from EXOSAT, Ginga and OSSE. These results confirm that the apparent discrepancy between the results of Ginga (with \\alpha \\simeq 0.9) and the previous results of EXOSAT and HEAO (with \\alpha \\simeq 0.7) is indeed due to ionized absorption and Compton reflection first taken into account for Ginga but...

  3. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs: III - Location and Energetics

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.

    2012-01-01

    Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval approx.0.0003-0.03pc (approx.10(exp 2)-10(exp 4)tau(sub s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between approx.0.01- 1 Stellar Mass/y, corresponding to approx. or >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are logE(sub K) approx. or = 42.6-44.6 erg/s. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN r.osmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyferts galaxies .

  4. Evidence for ultrafast outflows in radio-quiet AGNs - III. Location and energetics

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.

    2012-05-01

    Using the results of a previous X-ray photoionization modelling of blueshifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this Letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval ˜0.0003-0.03 pc (˜ 102-104rs) from the central black hole, consistent with what is expected for accretion disc winds/outflows. The mass outflow rates are constrained between ˜0.01 and 1 M⊙ yr-1, corresponding to >rsim5-10 per cent of the accretion rates. The average lower/upper limits on the mechanical power are log? 42.6-44.6 erg s-1. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN cosmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyfert galaxies.

  5. An X-Shooter composite of bright 1 < z < 2 quasars from UV to infrared

    Science.gov (United States)

    Selsing, J.; Fynbo, J. P. U.; Christensen, L.; Krogager, J.-K.

    2016-01-01

    Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1 github.com/jselsing/QuasarComposite

  6. Radio-quiet and radio-loud pulsars: similar in Gamma-rays but different in X-rays

    CERN Document Server

    Marelli, M; De Luca, A; Parkinson, P M Saz; Salvetti, D; Hartog, P R Den; Wolff, M T

    2015-01-01

    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet Gamma-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from Gamma-ray pulsar timing. For PSR J2030+4415 we found evidence for an about 10 arcsec-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. 2011 and confirm that, on average, the Gamma-ray--to--X-ray flux ratios (Fgamma/Fx) of radio-quiet pulsars are higher than for the radio-loud ones. Furthermore, while the Fgamma/Fx distribution features a single peak for the radio-quiet pulsars, the distribution is more dispersed for the radio-loud ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  7. Multiwavelength polarization observations of the γ-ray bright quasar PKS 0420-014

    Directory of Open Access Journals (Sweden)

    Troitskiy I.S.

    2013-12-01

    Full Text Available We analyze total and polarized intensity images of the quasar PKS 0420-014 obtained monthly with the VLBA at 43 GHz during 2008–2012 along with γ-ray data provided by the Fermi Large Area Telescope and multi-color photometric and polarimetric measurements collected by different optical telescopes. During this period the quasar underwent a number of optical flares, which were accompanied by rapid rotation of polarization angle, an increase of activity in γ-rays, and the appearance of new superluminal knots in the parsec-scale jet. We investigate the fine structure of the flares at different wavelengths and in polarized light, and determine kinematic parameters of the knots. We compare the rapid evolution of the optical polarization with the polarization of the VLBI core and knots. We interpret the multi-wavelength behavior within a model that places the blazar “dissipation zone” at the millimeter-wave core of the parsec-scale jet.

  8. THE HALO OCCUPATION DISTRIBUTION OF X-RAY-BRIGHT ACTIVE GALACTIC NUCLEI: A COMPARISON WITH LUMINOUS QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, Jonathan [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60605 (United States); Chatterjee, Suchetana; Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82072 (United States); Zheng Zheng [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Hickox, Ryan, E-mail: jonathan.richardson@uchicago.edu, E-mail: schatte1@uwyo.edu [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)

    2013-09-10

    We perform halo occupation distribution (HOD) modeling of the projected two-point correlation function (2PCF) of high-redshift (z {approx} 1.2) X-ray-bright active galactic nuclei (AGNs) in the XMM-COSMOS field measured by Allevato et al. The HOD parameterization is based on low-luminosity AGNs in cosmological simulations. At the median redshift of z {approx} 1.2, we derive a median mass of 1.02{sub -0.23}{sup +0.21} Multiplication-Sign 10{sup 13} h{sup -1} M{sub sun} for halos hosting central AGNs and an upper limit of {approx}10% on the AGN satellite fraction. Our modeling results indicate (at the 2.5{sigma} level) that X-ray AGNs reside in more massive halos compared to more bolometrically luminous, optically selected quasars at similar redshift. The modeling also yields constraints on the duty cycle of the X-ray AGN, and we find that at z {approx} 1.2 the average duration of the X-ray AGN phase is two orders of magnitude longer than that of the quasar phase. Our inferred mean occupation function of X-ray AGNs is similar to recent empirical measurements with a group catalog and suggests that AGN halo occupancy increases with increasing halo mass. We project the XMM-COSMOS 2PCF measurements to forecast the required survey parameters needed in future AGN clustering studies to enable higher precision HOD constraints and determinations of key physical parameters like the satellite fraction and duty cycle. We find that N {sup 2}/A {approx} 5 Multiplication-Sign 10{sup 6} deg{sup -2} (with N the number of AGNs in a survey area of A deg{sup 2}) is sufficient to constrain the HOD parameters at the 10% level, which is easily achievable by upcoming and proposed X-ray surveys.

  9. A proposed space mission around the Moon to measure the Moon Radio-Quiet Zone

    Science.gov (United States)

    Antonietti, N.; Pagana, G.; Pluchino, S.; Maccone, C.

    In a series of papers published since 2000 mainly in Acta Astronautica the senior author Maccone dealt with the advantages of the Farside of the Moon for future utilization Clearly the Moon Farside is free from RFI Radio Frequency Interference produced in larger and larger amounts by the increasing human exploitation of radio technologies That author suggested that crater Daedalus located at the center of the Farside was the best possible location to build up in the future one or more radiotelescopes or phased arrays to achieve the maximum sensitivity in radioastronomical and SETI searches Also a radio-quiet region of space above the Farside of the Moon exists and is called the Quiet Cone The Quiet Cone actual size however is largely unknown since it depends on the orbits of radio-emitting satellites around the Earth that are themselves largely unknown due to the military involvements In addition diffraction of electromagnetic waves grazing the surface of the Moon causes further changes in the geometrical shape of the Quiet Cone This riddle can be solved only by direct measurements of the radio attenuation above the Farside of the Moon performed by satellites orbiting the Moon itself In this paper we propose to let one or more low cost radiometers be put into orbit around the Moon to measure the RFI attenuation at different frequencies and altitudes above the Moon The opportunity of adding more payload s such as an ion detector and or a temperature sensor is evaluated also In this regard we present in this paper the experience gained by

  10. Estimating the size of a radio quiet zone for the radio astronomy service

    Science.gov (United States)

    Peng, Bo; Han, Wenjun

    2009-12-01

    The size of a radio quiet zone (RQZ) is largely determined by transmission losses of interfering signals, which can be divided into free space loss and diffraction loss. The free space loss is dominant. The diffraction loss presented in this paper is described as unified smooth spherical and knife edge diffractions, which is a function of minimum path clearance. We present a complete method to calculate the minimum path clearance. The cumulative distribution of the lapse rate of refractivity ( g n ), between the earth surface and 1 km above, is studied by using Chinese radio climate data. Because the size of an RQZ is proportional to g n , the cumulative distribution of g n can be used as an approximation for the size of the RQZ. When interference originates from mobile communication or television transmissions at a frequency of 408 MHz, and overline {g_n } is 40 N/km, where the refractivity N=left( {n-1} right) × 10^6, the size of the RQZ would be 180 km for a mobile source or 210 km for a television source, with a probability in the range of 15-100% in different months and for different stations. When speaking of the size of an RQZ, the radius in the case of a circular zone is implied. It results that a size of an RQZ is mainly influenced by transmission loss rather than effective radiated power. In the case where the distance between an interfering source and a radio astronomical observatory is about 100 km, at a frequency of 408 MHz, the allowable effective radiated power of the interfering source should be less than -30 dBW with a probability of about 85% for overline {g_n } equals 40 N/km, or -42 dBW with a probability less than 1 % for overline {g_n } equals 80 N/km.

  11. Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

    Science.gov (United States)

    Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; Mcclintock, J. E.

    1980-01-01

    The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

  12. Growing the first bright quasars in cosmological simulations of structure formation

    Science.gov (United States)

    Sijacki, Debora; Springel, Volker; Haehnelt, Martin G.

    2009-11-01

    We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. As a promising host system of a powerful high-redshift quasar, we select the most massive dark matter halo at z = 6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 105Msolar, and that seeding occurs around z ~ 15 in dark matter haloes of mass ~109-1010Msolar, we find that it is possible to build up supermassive BHs (SMBHs) by z = 6 that assemble most of their mass during extended Eddington-limited accretion periods. The properties of the simulated SMBHs are consistent with observations of z = 6 quasars in terms of the estimated BH masses and bolometric luminosities, the amount of star formation occurring within the host halo, and the presence of highly enriched gas in the innermost regions of the host galaxy. After a peak in the BH accretion rate at z = 6, the most massive BH has become sufficiently massive for the growth to enter into a much slower phase of feedback-regulated accretion. We extend our basic BH model by incorporating prescriptions for the BH recoils caused by gravitational wave emission during BH merger events, taking into account the newest numerical relativity simulations of merging BH binaries. In order to explore the full range of expected recoils and radiative efficiencies, we also consider models with spinning BHs. In the most `pessimistic' case where BH spins are initially high, we find that the growth of the SMBHs can be potentially hampered if they grow mostly in isolation and experience only a small number of mergers. On the other hand, whereas BH kicks can expel a substantial fraction of low-mass BHs, they do not significantly affect the build-up of the SMBHs. On the contrary, a

  13. Growing the first bright quasars in cosmological simulations of structure formation

    CERN Document Server

    Sijacki, Debora; Haehnelt, Martin G

    2009-01-01

    We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. We select the most massive dark matter halo at z=6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 10^5 Msun, and that seeding occurs around z~15 in dark matter haloes of mass 10^9-10^10 Msun, we find that it is possible to build up supermassive BHs (SMBHs) by z=6 that assemble most of their mass during extended Eddington-limited accretion periods. The properties of the simulated SMBHs are consistent with observations of z=6 quasars in terms of the estimated BH masses and bolometric luminosities, the amount of star formation occurring within the host halo, and the presence of highly enriched gas in the innermost regions of the host galaxy. After a pea...

  14. Black-hole mass estimates for a homogeneous sample of bright flat-spectrum radio quasars

    CERN Document Server

    Castignani, Gianluca; Lapi, Andrea; De Zotti, Gianfranco; Celotti, Annalisa; Danese, Luigi

    2013-01-01

    We have selected a complete sample of flat-spectrum radio quasars (FSRQs) from the WMAP 7-yr catalog within the SDSS area, all with measured redshift, and have compared the black hole mass estimates based on fitting a standard accretion disk model to the `blue bump' with those obtained from the commonly used single epoch virial method. The sample comprises 79 objects with a flux density limit of 1 Jy at 23 GHz, 54 of which (68%) have a clearly detected `blue bump'. Thirty-four of the latter have, in the literature, black hole mass estimates obtained with the virial method. The mass estimates obtained from the two methods are well correlated. If the calibration factor of the virial relation is set to $f=4.5$, well within the range of recent estimates, the mean logarithmic ratio of the two mass estimates is equal to zero with a dispersion close to the estimated uncertainty of the virial method. The fact that the two independent methods agree so closely in spite of the potentially large uncertainties associated ...

  15. The Large-Scale Structure view on the Galaxy-Quasar-AGN connection

    CERN Document Server

    Magliocchetti, M

    2006-01-01

    Combined investigations of the clustering properties of galaxies of different spectral type and high-redshift quasars strongly suggest local ellipticals to be the parent population of optically bright Active Galactic Nuclei (AGN). However, the picture gets more blurred when one extends the analysis to that class of AGNs which show enhanced radio emission. Objects belonging to this class in fact are found to be associated with structures which are about an order of magnitude more massive than those that host radio-quiet AGNs. Also, masses for the black holes engines of radio-enhanced AGN emission turn out to be systematically higher than those which fuel 'normal' quasars. On the other hand, the level of radio-activity in radio-luminous objects does not seem to be connected with black hole/host galaxy mass, at variance with what found in the optical case. These results, together with evidences for different cosmological evolutions of different types of AGNs pose a serious challenge to all those models aiming at...

  16. Optical spectra and radio properties of quasars

    International Nuclear Information System (INIS)

    Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

  17. Distribution of the very first PopIII stars and their relation to bright z~6 quasars

    CERN Document Server

    Trenti, M

    2007-01-01

    We discuss the link between dark matter halos hosting the first PopIII stars and the rare, massive, halos that are generally considered to host bright quasars at high redshift z~6. The main question that we intend to answer is whether the super-massive black holes powering these QSOs grew out from the seeds planted by the first intermediate massive black holes created in the universe. This question involves a dynamical range of 10^13 in mass and we address it by combining N-body simulations of structure formation to identify the most massive halos at z~6 with a Monte Carlo method based on linear theory to obtain the location and formation times of the first light halos within the whole simulation box. We show that the descendants of the first ~10^6 Msun virialized halos do not, on average, end up in the most massive halos at z~6, but rather live in a large variety of environments. The oldest PopIII progenitors of the most massive halos at z~6, form instead from density peaks that are on average one and a half...

  18. A unique UV flare in the optical light curve of the quasar J004457.9+412344

    Directory of Open Access Journals (Sweden)

    Hatzidimitriou D.

    2012-12-01

    Full Text Available We found that the nova candidate J004457.9+412344 is a radio-quiet quasar at z ∼ 2. Its optical long-term light curve, covering more than half a century, shows quasar typical flux variations superimposed by a spectacular single flare lasting more than one year (observer frame. We could not find comparable light curves among the several thousand catalogued radio-quiet quasars in the stripe 82 of the Sloan Digital Sky Survey. The decreasing part of the flare light curve roughly follows a power law t−5/3. The quasar spectrum, the total energy of the flare, and the decline of the light curve are consistent with the tidal disruption of a ∼10 Mʘ giant star by a supermassive black hole of a few 108 Mʘ. We argue that the alternative explanation by gravitational microlensing is less likely, though it cannot be definitely excluded.

  19. Double Lobed Radio Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    de Vries, W H; Becker, R H; White, R L

    2005-11-10

    We have combined a sample of 44 984 quasars, selected from the Sloan Digital Sky Survey (SDSS) Data Release 3, with the FIRST radio survey. Using a novel technique where the optical quasar position is matched to the complete radio environment within 450'', we are able to characterize the radio morphological make-up of what is essentially an optically selected quasar sample, regardless of whether the quasar (nucleus) itself has been detected in the radio. About 10% of the quasar population have radio cores brighter than 0.75 mJy at 1.4 GHz, and 1.7% have double lobed FR2-like radio morphologies. About 75% of the FR2 sources have a radio core (> 0.75mJy). A significant fraction ({approx}40%) of the FR2 quasars are bent by more than 10 degrees, indicating either interactions of the radio plasma with the ICM or IGM. We found no evidence for correlations with redshift among our FR2 quasars: radio lobe flux densities and radio source diameters of the quasars have similar distributions at low (mean 0.77) and high (mean 2.09) redshifts. Using a smaller high reliability FR2 sample of 422 quasars and two comparison samples of radio-quiet and non-FR2 radio-loud quasars, matched in their redshift distributions, we constructed composite optical spectra from the SDSS spectroscopic data. Based on these spectra we can conclude that the FR2 quasars have stronger high-ionization emission lines compared to both the radio quiet and non-FR2 radio loud sources. This is consistent with the notion that the emission lines are brightened by ongoing shock ionization of ambient gas in the quasar host as the radio source expands.

  20. Super- and Sub-critical Regions in Shocks driven by Radio-Loud and Radio-Quiet CMEs

    CERN Document Server

    Bemporad, Alessandro

    2012-01-01

    White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a "radio-loud" fast CME, while the second one was a "radio quiet" slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfv\\'en Mach numbers for the general case of an oblique shock. It turns out that the "radio-loud" CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the "radio-quiet" CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles.

  1. The Global Implications of the Hard Excess. II. Analysis of the Local Population of Radio-quiet AGNs

    Science.gov (United States)

    Tatum, M. M.; Turner, T. J.; Miller, L.; Reeves, J. N.; DiLiello, J.; Gofford, J.; Patrick, A.; Clayton, M.

    2016-02-01

    Active galactic nuclei (AGNs) show evidence for reprocessing gas, outflowing from the accreting black hole. The combined effects of absorption and scattering from the circumnuclear material likely explain the “hard excess” of X-ray emission above 20 keV, compared with the extrapolation of spectra from lower X-ray energies. In a recent Suzaku study, we established that the ubiquitous hard excess in hard, X-ray-selected, radio-quiet type 1 AGNs is consistent with a reprocessing of the X-ray continuum in an ensemble of clouds, located tens to hundreds of gravitational radii from the nuclear black hole. Here we add hard X-ray-selected, type 2 AGNs to extend our original study and show that the gross X-ray spectral properties of the entire local population of radio-quiet AGNs may be described by a simple unified scheme. We find a broad, continuous distribution of spectral hardness ratio and Fe Kα equivalent width across all AGN types, which can be reproduced by varying the observer's sightline through a single, simple model cloud ensemble, provided that the radiative transfer through the model cloud distribution includes not only photoelectric absorption but also three-dimensional (3D) Compton scattering. Variation in other parameters of the cloud distribution, such as column density or ionization, should be expected between AGNs, but such variation is not required to explain the gross X-ray spectral properties.

  2. The Global Implications of the Hard Excess II: Analysis of the Local population of Radio Quiet AGN

    CERN Document Server

    Tatum, M M; Miller, L; Reeves, J N; DiLiello, J; Gofford, J; Patrick, A; Clayton, M

    2015-01-01

    Active galactic nuclei (AGN) show evidence for reprocessing gas, outflowing from the accreting black hole. The combined effects of absorption and scattering from the circumnuclear material likely explains the `hard excess' of X-ray emission above 20 keV, compared with extrapolation of spectra from lower X-ray energies. In a recent {\\it Suzaku} study, we established the ubiquitous hard excess in hard X-ray-selected, radio-quiet type\\,1 AGNs to be consistent with reprocessing of the X-ray continuum an ensemble of clouds, located tens to hundreds of gravitational radii from the nuclear black hole. Here we add hard X-ray-selected, type\\,2 AGN to extend our original study and show that the gross X-ray spectral properties of the entire local population of radio quiet AGN may be described by a simple unified scheme. We find a broad, continuous distribution of spectral hardness ratio and Fe\\,K$\\alpha$ equivalent width across all AGN types, which can be reproduced by varying the observer's sightline through a single, ...

  3. Bright [CII] and dust emission in three z>6.6 quasar host galaxies observed by ALMA

    CERN Document Server

    Venemans, B P; Zschaechner, L; Decarli, R; De Rosa, G; Findlay, J R; McMahon, R G; Sutherland, W J

    2015-01-01

    We present ALMA detections of the [CII] 158 micron emission line and the underlying far-infrared continuum of three quasars at 6.6~6 quasar hosts correlate with the quasar's bolometric luminosity. In one quasar, the [CII] line is significantly redshifted by ~1700 km/s with respect to the MgII broad emission line. Comparing to values in the literature, we find that, on average, the MgII is blueshifted by 480 km/s (with a standard deviation of 630 km/s) with respect to the host galaxy redshift, i.e. one of our quasars is an extreme outlier. Through modeling we can rule out a flat rotation curve for our brightest [CII] emitter. Finally, we find that the ratio of black hole mass to host galaxy (dynamical) mass is higher by a factor 3-4 (with significant scatter) than local relations.

  4. Kes 73: A Young Supernova Remnant with an X-ray Bright, Radio-quiet Central Source

    OpenAIRE

    Gotthelf, E. V.; Vasisht, G.

    1997-01-01

    We clarify the nature of the small-diameter supernova remnant (SNR) Kes 73 and its central compact source, 1E 1841-045, using X-ray data acquired with the ASCA Observatory. We introduce a spatio-spectral decomposition technique necessary to disentangle the ASCA spectrum of the compact source from the barely resolved shell-type remnant. The source spectrum (1 - 8 keV) is characterized by an absorbed power-law with a photon index ~ 3.4 and N_H ~ 3.0E22 cm^-2, possibly non-thermal in nature. Thi...

  5. The Connection among Gamma-ray Burst Host-Galaxies, BL Lacs and Quasars

    OpenAIRE

    Rej, A.

    1999-01-01

    A possible connection among host-galaxies of gamma-ray bursts, BL Lacs and quasars is analysed. It is believed that the gamma-ray bursts, which do not show radio or infrared emission, occur in faint blue dwarf galaxies, that are seen around radio-quiet quasars, which lie in clusters. The GRB counterparts, which show radio emission, may be associated with more evolved starbursting environments, and arise from red galaxies, that are observed around some radio-loud quasars lying in richer cluste...

  6. Search for differences between radio-loud and radio-quiet gamma-ray pulsar populations with Fermi-LAT data

    CERN Document Server

    Sokolova, E V

    2016-01-01

    Observations by Fermi LAT enabled us to explore the population of non-recycled gamma-ray pulsars with the set of 89 objects. It was recently noted that there are apparent differences in properties of radio-quiet and radio-loud subsets. In particular, average observed radio-loud pulsar is younger than radio-quiet one and is located at smaller galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most of radio-loud pulsars are first discovered in the radio-band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi LAT data alone using all point sources from 3FGL catalog as the candidates. Unlike preceding blind search, the present catalog is constructed with novel semi-coherent method and covers the full range of characteristic ages down to 1 kyr. The search resulted in the catalog of 40 non-recycled pulsars, 26 of which are radio-quiet. There are no statistically si...

  7. Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuStar: Compton-Thick Absorption or Intrinsic X-Ray Weakness?

    Science.gov (United States)

    Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W..; Fabian, A. C.; Farrah, D.; Fiore, F.; Fuerst, F.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R.; Madsen, K. K.; Matt, G.; Ogle, P.; Risaliti, G.; Saez, C.; Teng, S. H.; Walton, D. J.; Zhang, W. W.

    2013-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain approx. or equal to 400-600 hard X-ray (is greater than or equal to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed N(sub H) is less than or equal to 10(exp24) cm(exp-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N(sub H) 7 × 10(exp 24) cm(exp-2) if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe Ka line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  8. Spectral Variability in Radio-Loud Quasars

    Indian Academy of Sciences (India)

    Minfeng Gu

    2014-09-01

    The spectral variability of a sample of 44 Flat-Spectrum Radio Quasars (FSRQs) and 18 Steep-Spectrum Radio Quasars (SSRQs) in SDSS stripe 82 region is investigated. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows a redder-when-brighter trend, which is in contrast to our previous results. Eight of 18 SSRQs display a BWB. We found an anticorrelation between the Eddington ratio and the variability amplitude in the band for SSRQs, which is similar to that in radio-quiet AGNs. This implies that the thermal emission from the accretion disk may be responsible for the variability in SSRQs. The spectral variability from SDSS multi-epoch spectroscopy also shows BWB for several SSRQs, which is consistent with that from photometry.

  9. TYPE 1 AND TYPE 2 QUASARS IN THE MID-INFRARED

    Directory of Open Access Journals (Sweden)

    S. E. Ridgway

    2009-01-01

    Full Text Available Type 2 or \\obscured" AGN have long been identi ed at low AGN luminosities (e.g. Seyfert 2s or through their radio luminosities (e.g. radio galaxies. But radio-quiet quasars (RQQs are many times more common than radio-loud quasars, and it's therefore unsurprising that recent searches have revealed that radio-quiet quasar 2s also form a signi cant population. Finding the numbers, properties, and redshift distribution of quasar 2s will be very important to resolving questions about the formation and co-evolution of black holes and galaxies. We have selected a sample of Type 2 and Type 1 quasars matched in their mid-infrared luminosity from the Spitzer First Look Survey by selecting on their mid-infrared dust emission properties (as measured by Spitzer IRAC photometry. This emission provides a distinctive signature of AGN activity but should not be a cted by orientation or torus opening angle. We have obtained mid-infrared IRS spectroscopy of these samples to study star formation activity in the host galaxies and the dust environments of the AGN, using measurements of the PAH features, the shape of the mid-infrared SED, and the equivalent width of the silicate features at 10 microns. We nd that the quasar 2s have more diverse mid-IR spectral properties, and that obscuration of the AGN is linked to star formation activity in the host.

  10. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    CERN Document Server

    Tombesi, F; Reeves, J N; Palumbo, G G C; Braito, V; Dadina, M

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\sim100,000km/s (\\sim0.3c), with a peak and mean value of \\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6erg s^{-1} cm, with a mean value of log\\xi 4.2 erg s^{-1} cm. The associated column densities are also large, in the range N_H\\sim10^{22}-10^{24...

  11. Bright [CII] 158$\\mu$m emission in a quasar host galaxy at $z=6.54$

    CERN Document Server

    Bañados, E; Walter, F; Venemans, B P; Farina, E P; Fan, X

    2015-01-01

    The [CII] 158$\\mu$m fine-structure line is known to trace regions of active star formation and is the main coolant of the cold, neutral atomic medium. In this \\textit{Letter}, we report a strong detection of the [CII] line in the host galaxy of the brightest quasar known at $z>6.5$, the Pan-STARRS1 selected quasar PSO J036.5078+03.0498 (hereafter P036+03), using the IRAM NOEMA millimeter interferometer. Its [CII] and total far-infrared luminosities are $(5.8 \\pm 0.7) \\times 10^9 \\,L_\\odot$ and $(7.6\\pm1.5) \\times 10^{12}\\,L_\\odot$, respectively. This results in a $L_{[CII]} /L_{TIR}$ ratio of $\\sim 0.8\\times 10^{-3}$, which is at the high end for those found for active galaxies, though it is lower than the average found in typical main sequence galaxies at $z\\sim 0$. We also report a tentative additional line which we identify as a blended emission from the $3_{22} - 3_{13}$ and $5_{23} - 4_{32}$ H$_2$O transitions. If confirmed, this would be the most distant detection of water emission to date. P036+03 riva...

  12. Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects Superluminal Motion of Gamma-Ray Bright Blazars

    CERN Document Server

    Jorstad, S G; Mattox, J R; Wehrle, A E; Bloom, S D; Yurchenko, A V; Jorstad, Svetlana G; Marscher, Alan P; Mattox, John R; Wehrle, Ann E; Bloom, Steven D; Yurchenko, Alexei V

    2001-01-01

    We present the results of a program to monitor the structure of the radio emission in 42 $\\gamma$-ray bright blazars (31 quasars and 11 BL Lac objects) with the VLBA at 43, 22, and occasionally 15 and 8.4 GHz, over the period from November 1993 to July 1997. We determine proper motions in 33 sources and find that the apparent superluminal motions in $\\gamma$-ray sources are much faster than for the general population of bright compact radio sources. This follows the strong dependence of the $\\gamma$-ray flux on the level of relativistic beaming for both external-radiation Compton and synchrotron self-Compton emission. There is a positive correlation (correlation coefficient $r$=0.45) between the flux density of the VLBI core and the $\\gamma$-ray flux and a moderate correlation (partial correlation coefficient $r$=0.31) between $\\gamma$-ray apparent luminosity and superluminal velocities of jet components, as expected if the $\\gamma$-ray emission originates in a very compact region of the relativistic jet and ...

  13. Absorption lines and the radio structure of quasars

    International Nuclear Information System (INIS)

    High angular resolution radio observations at lambda6cm of 20 quasars are presented, all but two of which have been selected from a sample used by previous authors for a survey of absorption lines. The additional two, 1246-057 and 1333 + 286, are quasars with broad absorption lines and appear to be radio quiet. The radio structures for the entire sample of 66 sources of the previous authors are summarized and an investigation is made of whether the radio structure might provide clues on understanding the origin of the absorption lines in the range Zsub(em)-Zsub(ab) approx. 3000-18000 kms-1. The frequency of occurrence of absorption lines appears to be similar for both radio and optically selected quasars. (author)

  14. ISO Observations of the dusty quasar BR1202-0725

    CERN Document Server

    Leech, K J; Metcalfe, L

    2001-01-01

    We present mid- and far-IR photometry of the high-redshift (z=4.69) dusty quasar BR1202-0725. The quasar was detected in the near-IR, at a flux level (0.7+/-0.2 mJy) consistent with an average Radio-Quiet Quasar at it's redshift. Only upper limits for the emission were obtained in the far-IR. These upper limits, when combined with data from ground-based telescopes, are the first direct evidence for a turn-over in the far-IR emission and hence confirm that a black-body dominates the SED at FIR wavelengths. This black-body is most probably cool dust, constrained to have a temperature below 80K, for a beta of 1.5.

  15. Direct Microlensing-Reverberation Observations of the Intrinsic Magnetic Structure of Active Galactic Nuclei in Different Spectral States: A Tale of Two Quasars

    Science.gov (United States)

    Schild, Rudolph E.; Leiter, Darryl J.; Robertson, Stanley L.

    2008-03-01

    We show how direct microlensing-reverberation analysis performed on two well-known quasars (Q2237, the Einstein Cross, and Q0957, the Twin) can be used to observe the inner structure of two quasars which are in significantly different spectral states. These observations allow us to measure the detailed internal structure of Q2237 in a radio-quiet high-soft state, and compare it to Q0957 in a radio-loud low-hard state. When taken together we find that the observed differences in the spectral states of these two quasars can be understood as being due to the location of the inner radii of their accretion disks relative to the co-rotation radii of the magnetospheric eternally collapsing objects (MECO) in the centers of these quasars. The radiating structures observed in these quasars are associated with standard accretion disks and outer outflow structures, where the latter are the major source of UV-optical continuum radiation. While the observed inner accretion disk structure of the radio-quiet quasar Q2237 is consistent with either a MECO or a black hole, the observed inner structure of the radio-loud quasar Q0957 can only be explained by the action of the intrinsic magnetic propeller of a MECO with its accretion disk. Hence a simple and unified answer to the long-standing question: "Why are some quasars radio loud?" is found if the central objects of quasars are MECO, with radio-loud and radio-quiet spectral states similar to the case of galactic black hole candidates.

  16. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    Energy Technology Data Exchange (ETDEWEB)

    Romanishin, W.; Hintzen, P. (Arizona State Univ., Tempe (USA); NASA, Goddard Space Flight Center, Greenbelt, MD (USA))

    1989-06-01

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud. 28 refs.

  17. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    International Nuclear Information System (INIS)

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud. 28 refs

  18. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    Science.gov (United States)

    Romanishin, W.; Hintzen, Paul

    1989-01-01

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud.

  19. Color Effects Associated with the 1999 Microlensing Brightness Peaks in Gravitationally Lensed Quasar Q2237+0305

    CERN Document Server

    Vakulik, V G; Dudinov, V N; Minakov, A A; Nuritdinov, S N; Tsvetkova, V S; Zheleznyak, A P; Konichek, V V; Sinelnikov, I Y; Burkhonov, O M; Artamonov, B P; Bruevich, V V

    2003-01-01

    Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is presented. Monitoring of Q2237+0305 in July-October 2000, made at nearly daily basis, did not reveal rapid (night-to-night and intranight) variations of brightness of the components during this time period. Rather slow changes of magnitudes of the components were observed, such as 0.08 mag fading of B and C components and 0.05 mag brightening of D in R band during July 23 - October 7, 2000. By good luck three nights in 1999 were almost at the time of the strong brightness peak of image C, and approximately in the middle of the ascending slope of the image A brightness peak. The C component was the most blue one in the system in 1998 and 1999, having changed its (V-I) color from 0.56 mag to 0.12 mag since August 1997, while its brightness increased almost 1.2 mag during this time period. The A component behaved similarly between August 1998 and August 2000, hav...

  20. On the Radio and Optical Luminosity Evolution of Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; /KIPAC, Menlo Park /SLAC; Petrosian, V.; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.; Lawrence, A.; /Edinburgh U., Inst. Astron.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.

    2011-05-20

    We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness R defined as the ratio of radio and optical luminosities, using a flux limited data set containing 636 quasars with radio and optical fluxes from White et al. We first note that when dealing with multivariate data it is imperative to first determine the true correlations among the variables, not those introduced by the observational selection effects, before obtaining the individual distributions of the variables. We use the methods developed by Efron and Petrosian which are designed to obtain unbiased correlations, distributions, and evolution with redshift from a data set truncated due to observational biases. It is found that as expected the population of quasars exhibits strong positive correlation between the radio and optical luminosities and that this correlation deviates from a simple linear relation in a way indicating that more luminous quasars are more radio loud. We also find that there is a strong luminosity evolution with redshift in both wavebands, with significantly higher radio than optical evolution. We conclude that the luminosity evolution obtained by arbitrarily separating the sources into radio loud (R > 10) and radio quiet (R < 10) populations introduces significant biases that skew the result considerably. We also construct the local radio and optical luminosity functions and the density evolution. Finally, we consider the distribution of the radio loudness parameter R obtained from careful treatment of the selection effects and luminosity evolutions with that obtained from the raw data without such considerations. We find a significant difference between the two distributions and no clear sign of bi-modality in the true distribution. Our results indicate therefore, somewhat surprisingly, that there is no critical switch in the efficiency of the production of disk outflows/jets between very radio quiet and very radio

  1. Testing Disk-Wind Models with Quasar CIV 1549Å Associated Absorption Lines

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2012-01-01

    Narrow associated C IV 1549Å absorption lines (NALs) with a rest equivalent width EW =3 Å detected in z ˜ 2 radio-loud and radio-quiet quasars, (a) exhibit evidence of an origin in radiatively accelerated gas, and (b) may be closely related to broad absorption line (BAL) outflows. These NALs......-ray to UV emission ratio, i.e., aOX. The latter means that quasars with flat aOX (like radio-louds) should not have strong, high-velocity (BAL-like) outflows. These results are of interest not only to studies of disk wind scenarios and quasar structure, but also to studies of quasar feedback: NALs...

  2. The AGN content of deep radio surveys and radio emission in radio-quiet AGN. Why every astronomer should care about deep radio fields

    CERN Document Server

    Padovani, P; Miller, N; Kellermann, K I; Mainieri, V; Rosati, P; Tozzi, P; Vattakunnel, S

    2014-01-01

    We present our very recent results on the sub-mJy radio source populations at 1.4 GHz based on the Extended Chandra Deep Field South VLA survey, which reaches ~ 30 {\\mu}Jy, with details on their number counts, evolution, and luminosity functions. The sub-mJy radio sky turns out to be a complex mix of star-forming galaxies and radio-quiet AGN evolving at a similar, strong rate and declining radio-loud AGN. While the well-known flattening of the radio number counts below 1 mJy is mostly due to star-forming galaxies, these sources and AGN make up an approximately equal fraction of the sub-mJy sky. Our results shed also light on a fifty-year-old issue, namely radio emission from radio-quiet AGN, and suggest that it is closely related to star formation, at least at z ~ 1.5 - 2. The implications of our findings for future, deeper radio surveys, including those with the Square Kilometre Array, are also discussed. One of the main messages, especially to non-radio astronomers, is that radio surveys are reaching such f...

  3. Direct Microlensing-Reverberation Observations of the Intrinsic magnetic Structure of AGN in Different Spectral States: A Tale of Two Quasars

    CERN Document Server

    Schild, Rudolph E; Robertson, Stanley L

    2007-01-01

    We show how direct microlensing-reverberation analysis performed on two well-known Quasars (Q2237 - The Einstein Cross and Q0957 - The Twin) can be used to observe the inner structure of two quasars which are in significantly different spectral states. These observations allow us to measure the detailed internal structure of quasar Q2237 in a radio quiet high-soft state, and compare it to quasar Q0957 in a radio loud low-hard state. We find that the observed differences in the spectral states of these two quasars can be understood as being due to the location of the inner radii of their accretion disks relative to the co-rotation radii of rotating intrinsically magnetic supermassive compact objects in the centers of these quasars.

  4. Observed Quasar Structure

    Science.gov (United States)

    Schild, Rudolph E.

    2011-05-01

    With the introduction of microlensing (nano-lensing) and reverberation analysis, understanding of the luminous structure surrounding quasars has gone from theoretical speculation to an observer's sport. Micro-lensing with day timescale has demonstrated that quasars have structure on scales of 1 R_G which we attribute to the inner edge of the accretion disc, at central distance 70 R_G in lo-hard state (radio loud) Q0957 quasar, indicated by reverberation. Reverberation of the dominant optical continuum has been detected in all 55 hi-soft quasars with brightness data, originating in the dusty torus observed in UV-optical and IR reverberation. Microlensing simulation compared to brightness monitoring shows that 2/3 of the UV-optical continuum originates in the outer torus. The observed color effects observed in the microlensing support the existence of inner and outer luminous structure.

  5. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander

    2013-01-01

    The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...

  6. Radio Structures of Compact Quasars with Broad Absorption Lines

    Science.gov (United States)

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  7. Exploration of the Radio-Loud/Radio Quiet Dichotomy for QSO: Using Radio Morphology and 4D Eigenvector 1

    Science.gov (United States)

    Zamfir, Sebastian; Sulentic, J. W.; Marziani, P.; Dultzin, D.

    2007-12-01

    The reality of a RL/RQ Dichotomy for QSO remains an open problem. Recent studies not only provide us with contradictory results, but also display the confusion of comparing conclusions drawn on the basis of different views on "what means radio-loud"? We propose a definition of radio loudness based on three criteria (simultaneously applied): radio morphology, radio luminosity and radio-optical flux density ratio. Fanaroff-Riley II radio sources (FRIIs) are assumed to be the parent population of RL quasars, while the core dominated RL quasars are assumed to be preferentially aligned FRIIs. Orientation-unification then suggests the RQ-RL boundary is set by the least radio luminous FRII and by the lowest radio-optical ratio for an FRII. We also consider RL and RQ quasars in the context of a 4D Eigenvector 1 (4DE1) Parameter Space that is defined independently of any radio measure. Using Sloan Digital Sky Survey (SDSS) spectroscopic data for 400+ QSO (z<0.7 and brighter than psf g =17.5), coupled with FIRST and NVSS radio surveys (1.4GHz), we show that classical RL sources distribute very differently from the RQ majority of QSO.

  8. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

    Science.gov (United States)

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

  9. Evidence for Ultra-fast Outflows in Radio-quiet Active Galactic Nuclei. II. Detailed Photoionization Modeling of Fe K-shell Absorption Lines

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-11-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s-1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ~10,000 km s-1 (~0.03c) up to ~100,000 km s-1 (~0.3c), with a peak and mean value of ~42,000 km s-1 (~0.14c). The ionization parameter is very high and in the range log ξ ~ 3-6 erg s-1 cm, with a mean value of log ξ ~ 4.2 erg s-1 cm. The associated column densities are also large, in the range N H ~ 1022-1024 cm-2, with a mean value of N H ~ 1023 cm-2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can

  10. Host Galaxies of Luminous Quasars: Structural Properties and the Fundamental Plane

    Science.gov (United States)

    Wolf, Marsha J.; Sheinis, Andrew I.

    2008-10-01

    We present stellar velocity dispersion measurements in the host galaxies of ten luminous quasars (MV < -23) using the Ca H&K lines in off-nuclear spectra. We combine these data with effective radii and magnitudes from the literature to place the host galaxies on the fundamental plane (FP) where their properties are compared with other types of galaxies. We find that the radio-loud (RL) QSO hosts have similar properties to massive elliptical galaxies, while the radio-quiet (RQ) hosts are more similar to intermediate-mass galaxies. The RL hosts lie at the upper extreme of the FP due to their large velocity dispersions (langσ*rang = 321 km s-1), low surface brightness (langμ e (r)rang = 20.8 mag arcsec-2), and large effective radii (langRe rang = 11.4 kpc), and have langM *rang = 1.5 × 1012 M sun and langM/Lrang = 12.4. In contrast, properties of the RQ hosts are langσ*rang = 241 km s-1, langM *rang = 4.4 × 1011 M sun, and M/L ~ 5.3. The distinction between these galaxies occurs at σ*~ 300 km s-1, Re ~ 6 kpc, and corresponding M * ~ 5.9 ± 3.5 × 1011 M sun. Our data support previous results that Palomar-Green QSOs are related to gas-rich galaxy mergers that form intermediate-mass galaxies, while RL QSOs reside in massive early-type galaxies, most of which also show signs of recent mergers or interactions. Previous authors have drawn these conclusions by using estimates of the black hole mass and inferring host galaxy properties from that, while here we have relied purely on directly measured host galaxy properties.

  11. A Hybrid Spin-Down Model and its Application to the Radio Quiet X-Ray Pulsar 1E 1207.4-5209

    Institute of Scientific and Technical Information of China (English)

    张灵娣; 彭秋和; 罗新炼

    2003-01-01

    A series of newly published papers are focusing on the formation of the absorption features discovered by Chandra and XMM-Newton from the young radio quiet x-ray pulsar 1E 1207.4-5209. We try to interpret it as cyclotron absorption lines since this possibility could not be ruled out. With new development and application of a hybrid model, i.e., the magnetic dipole spin-down model combined with the neutrino cyclotron radiation spin-down model, we can easily avoid the contradiction between the normal rotation energy loss rate and the relatively lower magnetic field, and then we obtain the possible initial spin period (~0.420s). We suppose that the progenitor of 1E 1207.4-5209 may be a white dwarf.

  12. Evidence for ultra-fast outflows in radio-quiet AGNs. I. Detection and statistical incidence of Fe K-shell absorption lines

    Science.gov (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Yaqoob, T.; Braito, V.; Dadina, M.

    2010-10-01

    Context. Blue-shifted Fe K absorption lines have been detected in recent years between 7 and 10 keV in the X-ray spectra of several radio-quiet AGNs. The derived blue-shifted velocities of the lines can often reach mildly relativistic values, up to 0.2-0.4c. These findings are important because they suggest the presence of a previously unknown massive and highly ionized absorbing material outflowing from their nuclei, possibly connected with accretion disk winds/outflows. Aims: The scope of the present work is to statistically quantify the parameters and incidence of the blue-shifted Fe K absorption lines through a uniform analysis on a large sample of radio-quiet AGNs. This allows us to assess their global detection significance and to overcome any possible publication bias. Methods: We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. A simple uniform model composed by an absorbed power-law plus Gaussian emission and absorption lines provided a good fit for all the data sets. We derived the absorption lines parameters and calculated their detailed detection significance making use of the classical F-test and extensive Monte Carlo simulations. Results: We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies higher than 7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3 × 10-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability UFOs) those highly ionized absorbers with outflow velocities higher than 104 km s-1, then the majority of the lines are consistent with being associated to UFOs and the fraction of objects with detected UFOs in the whole sample is at least ~35%. This fraction is similar for type 1 and type 2 sources. The global covering fraction of

  13. Size and Structure of the Narrow-Line Region of Quasars

    CERN Document Server

    Bennert, N; Schulz, H; Wilson, A S; Wills, B J; Bennert, Nicola; Falcke, Heino; Schulz, Hartmut; Wilson, Andrew S.; Wills, Beverley J.

    2002-01-01

    We have observed the narrow-line regions (NLRs) of the seven brightest radio-quiet PG (or BQS) quasars (z < 0.5) with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST). Linear-ramp filters were used to image the [OIII] lambda 5007 line emission with 0.0455-0.1 arcsec pixel resolution. We find that the NLRs are very compact with typical extents of 2-4 arcsec. Two quasars show compact filamentary structures similar to Seyfert NLRs. They may be related to radio outflows. Most interestingly, when including a sample of Seyfert galaxies observed with HST, we tentatively find that the size of the NLR is proportional to the square root of the [OIII] luminosity. This is comparable to the scaling found for the size of the broad-line region with continuum luminosity, which has been interpreted in terms of a constant photoionization parameter. The relation determined here connects the NLR of radio-quiet quasars and Seyferts over three orders of magnitude in [OIII] luminosity.

  14. The Optical-UV Emissivity of Quasars: Dependence on Black Hole Mass and Radio Loudness

    Science.gov (United States)

    Shankar, Francesco; Calderone, Giorgio; Knigge, Christian; Matthews, James; Buckland, Rachel; Hryniewicz, Krzysztof; Sivakoff, Gregory; Dai, Xinyu; Richardson, Kayleigh; Riley, Jack; Gray, James; La Franca, Fabio; Altamirano, Diego; Croston, Judith; Gandhi, Poshak; Hönig, Sebastian; McHardy, Ian; Middleton, Matthew

    2016-02-01

    We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 ≤ z ≤ 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) α3000 continuum slopes ({L}ν \\propto {ν }α at 3000 Å) with increasing black hole mass, bluer α3000 with increasing luminosity at 3000 Å, and bluer α3000 with increasing spin of the black hole, when all other parameters are held fixed. We find no clear evidence for any of these predictions in the data. In particular, we find the following. (i) α3000 shows no significant dependence on black hole mass or luminosity. Dedicated Monte Carlo tests suggest that the substantial observational uncertainties in the black hole virial masses can effectively erase any intrinsic dependence of α3000 on black hole mass, in line with some previous studies. (ii) The mean slope α3000 of radio-loud sources, thought to be produced by rapidly spinning black holes, is comparable to, or even redder than, that of radio-quiet quasars. Indeed, although quasars appear to become more radio loud with decreasing luminosity, we still do not detect any significant dependence of α3000 on radio loudness. The predicted mean α3000 slopes tend to be bluer than in the data. Disk models with high inclinations and dust extinction tend to produce redder slopes closer to empirical estimates. Our mean α3000 values are close to the ones independently inferred at z < 0.5, suggesting weak evolution with redshift, at least for moderately luminous quasars.

  15. Unification of Luminous Type 1 Quasars through CIV Emission

    CERN Document Server

    Richards, Gordon T; Gallagher, S C; Hall, Patrick B; Hewett, Paul C; Leighly, Karen M; Deo, Rajesh P; Kratzer, Rachael M; Shen, Yue

    2010-01-01

    Using a sample of 30,000 quasars from SDSS-DR7, we explore the range of properties exhibited by high-ionization, broad emission lines, such as CIV 1549. Specifically we investigate the anti-correlation between L_UV and emission line EQW (the Baldwin Effect) and the "blueshifting" of high-ionization emission lines. The blueshift of the CIV emission line is nearly ubiquitous, with a mean shift of 810 km/s for radio-quiet (RQ) quasars and 360 km/s for radio-loud (RL) quasars, and the Baldwin Effect is present in both RQ and RL samples. Composite spectra are constructed as a function of CIV emission line properties in attempt to reveal empirical relationships between different line species and the SED. Within a two-component disk+wind model of the broad emission line region (BELR), where the wind filters the continuum seen by the disk component, we find that RL quasars are consistent with being dominated by the disk component, while BALQSOs are consistent with being dominated by the wind component. Some RQ object...

  16. On the puzzling high-energy pulsations of the energetic radio-quiet $\\gamma$-ray pulsar J1813$-$1246

    CERN Document Server

    Marelli, M; Pizzocaro, D; De Luca, A; Wood, K S; Caraveo, P; Salvetti, D; Parkinson, P M Saz; Acero, F

    2014-01-01

    We have analyzed the new deep {\\it XMM-Newton} and {\\it Chandra} observations of the energetic radio-quiet pulsar J1813$-$1246. The X-ray spectrum is non-thermal, very hard and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available {\\it Fermi} ephemeris to five years. We found two glitches. The $\\gamma$-ray lightcurve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardenning towards the bridge. The X-ray peaks lag the $\\gamma$-ray ones by 0.25 in phase. We found a hint of detection in the 30-500 keV band with {\\it INTEGRAL} IBIS/ISGRI, that is consistent with the extrapolation of bo...

  17. Evidence for ultra-fast outflows in radio-quiet AGNs: I - detection and statistical incidence of Fe K-shell absorption lines

    CERN Document Server

    Tombesi, F; Reeves, J N; Palumbo, G G C; Yaqoob, T; Braito, V; Dadina, M

    2010-01-01

    We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies E>7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3x10^-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability <10^-7. We identify the lines as Fe XXV and Fe XXVI K-shell resonant absorption. They are systematically blue-shifted, with a velocity distribution ranging from zero up to 0.3c, with a peak and mean value at 0.1c. We detect variability of the lines on both EWs and blue-shifted velocities among different observations even on time-scales as short as a few days, possibly suggesting somewhat compact absorbers. Moreover, we find no significant correlation between the cosmological red-sh...

  18. On the puzzling high-energy pulsations of the energetic radio-quiet γ-ray pulsar J1813–1246

    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Pizzocaro, D.; De Luca, A.; Caraveo, P.; Salvetti, D. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Harding, A. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Saz Parkinson, P. M. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Acero, F., E-mail: marelli@lambrate.inaf.it [Laboratoire AIM, CEA-IRFU/CNRS/Universit Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)

    2014-11-10

    We have analyzed the new deep XMM-Newton and Chandra observations of the energetic, radio-quiet pulsar J1813–1246. The X-ray spectrum is nonthermal, very hard, and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available Fermi ephemeris to five years. We found two glitches. The γ-ray light curve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardening toward the bridge. Surprisingly, both X-ray peaks lag behind the γ-ray ones by a quarter of phase. We found a hint of detection in the 30-500 keV band with INTEGRAL, which is consistent with the extrapolation of both the soft X-ray and γ-ray emission of J1813. The unique X-ray and γ-ray phasing suggests a singular emission geometry. We discuss some possibilities within the current pulsar emission models. Finally, we develop an alternative geometrical model where the X-ray emission comes from polar cap pair cascades.

  19. The ISO View of Palomar-Green Quasars

    Science.gov (United States)

    Haas, M.; Klaas, U.; Mueller, S. A. H.; Bertoldi, F.; Camenzind, M.; Chini, R.; Krause, O.; Lemke, D.; Meisenheimer; Richards, P. J.

    2003-01-01

    Mining the ISO data archive we provide the complete ISO view of PG quasars containing 64 infrared spectral energy distributions between 5 and 200 mu m. About half of the sample was supplemented by MAMBO and SCUBA (sub-)millimeter data. Since the PG quasars were selected optically, the high infrared detection rate of more than 80% suggests that every quasar possesses luminous to hyper-luminous dust emission with dust masses comparable to Seyferts and ultra-luminous IR galaxies (ULIRGs). The gas to-dust mass ratio (of those sources where CO measurements are available in the literature) is consistent with the galactic value providing further evidence for the thermal nature of the IR emission of radio quiet quasars. The SEDs represent templates of unprecedented detail and sensitivity. We suggest that the diversity of the SEDs reflects largely the evolution of the dust distribution, and we propose a classification of the SED shapes as well as an evolutionary scheme in which this variety can be understood. During the evolution the surrounding dust redistributes, settling more and more into a torus/disk like configuration, while the SEDs show an initial FIR bump, then an increasing MIR emission and a steeper near- to mid-infrared slope, both of which finally also decrease. Regarding cosmic evolution, our hyper-luminous quasars in the "local" universe at z=l do not show the hyper-luminous (LFIR >? 10(exp 13) L(sub sun)) starburst activity inferred for z=4 quasars detected in several (sub-)millimeter surveys. In view of several caveats this difference should be established further, but it already suggests that in the early dense universe stronger merger events led to more powerful starbursts accompanying the quasar phenomenon, while at later cosmic epochs any coeval starbursts obviously do not reach that high power and are outshone by the AGN. Additional information is included in the original extended abstract.

  20. Examining the Radio-Loud/Radio-Quiet dichotomy with new Chandra and VLA observations of 13 UGC galaxies

    CERN Document Server

    Kharb, Preeti; Axon, D J; Chiaberge, M; Grandi, P; Robinson, A; Giovannini, G; Balmaverde, B; Macchetto, D; Montez, R

    2012-01-01

    (Abridged) We present the results from new 15 ks Chandra-ACIS and 4.9 GHz Very Large Array observations of 13 galaxies hosting low luminosity AGN. This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti & Balmaverde (2005, 2006); Balmaverde & Capetti (2006). The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC6985). The new VLA observations improve the spatial resolution by a factor of ten: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as "core", "power-law" or "intermediate" galaxies. With more than...

  1. An X-Ray Study of Lobe-Dominated Radio-Loud Quasars with XMM-Newton

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We report on our results of X-ray spectral analysis for a sample of radio-loud quasars covering a wide range of the radio core-dominance parameter, R, from core-dominated to lobe-dominated objects, using data obtained mostly with the XMM-Newton Observatory. We find that the spectral shape of the underlying power-law continuum is flat even for the lobe-dominated objects (average photon index ~ 1.5), indistinguishable from that of core-dominated quasars. For lobe-dominated objects, contribution of X-rays from the jets is expected to be very small based on previous unification schemes, more than one order of magnitude lower than the observed X-ray luminosities. Assuming that radio-loud quasars follow the same X-ray-UV/optical luminosity relation for the disk-corona emission as found for radio-quiet quasars, we estimate the X-ray flux contributed by the disk-corona component from the optical/UV continuum. We find that neither the luminosity, nor the spectral shape, of the disk-corona X-ray emission can account for the bulk of the observed X-ray properties. Thus in lobe-dominated quasars, either the disk-corona X-ray emission is much enhanced in strength and flatter in spectral shape (photon index~1.5) compared to normal radio-quiet quasars, or their jet X-ray emission is much enhanced compared to their weak radio core-jet emission. If the latter is the case, our result may imply that the jet emission in X-rays is less Doppler beamed than that in the radio. As a demonstrating example, we test this hypothesis by using a specific model in which the X-ray jet has a larger opening angle than the radio jet.

  2. On the statistical characteristics of radio-loud and radio-quiet halo coronal mass ejections and their associated flares during solar cycles 23 and 24

    Science.gov (United States)

    Mittal, Nishant; Sharma, Joginder; Verma, Virendar Kumar; Garg, Vijay

    2016-08-01

    We have studied the characteristics of radio-loud (RL) and radio-quiet (RQ) front side halo coronal mass ejections (HCMEs) (angular width 360°) observed between the time period years 1996-2014. RL-HCMEs are associated with type II radio bursts, while RQ-HCMEs are not associated with type II radio bursts. CMEs near the Sun in the interplanetary medium associated with radio bursts also affect the magnetosphere. The type II radio burst data was observed by WIND/WAVES instrument and HCMEs were observed by LASCO/ SOHO instruments. In our study, we have examined the properties of RL-HCMEs and RQ-HCMEs and found that RL-HCMEs follow the solar cycle variation. Our study also shows that the 26% of slow speed HCMEs and 82% of fast speed HCMEs are RL. The average speed of RL-HCMEs and RQ-HCMEs are 1370 km/s and 727 km/s, respectively. Most of the RQ-HCMEs occur around the solar disc center while most of RL-HCMEs are uniformly distributed across the solar disc. The mean value of acceleration of RL-HCMEs is more than twice that of RQ-HCMEs and mean value of deceleration of RL- HCMEs is very small compare to RQ-HCMEs events. It is also found that RQ-HCMEs events are associated with C- and M-class of SXR flares, while RL-HCMEs events are associated with M and X-class of SXR flares, which indicates that the RQ-HCMEs are less energetic than the RL-HCMEs. We have also discussed the various results obtained in present investigation in view of recent scenario of solar physics.

  3. The Redshift Distribution of Intervening Weak MgII Quasar Absorbers and a Curious Dependence on Quasar Luminosity

    CERN Document Server

    Evans, Jessica L; Murphy, Michael T; Nielsen, Nikole M; Klimek, Elizabeth S

    2013-01-01

    We have identified 469 MgII doublet systems having W_r >= 0.02 {\\AA} in 252 Keck/HIRES and UVES/VLT quasar spectra over the redshift range 0.1 = 1.0 {\\AA}) absorbers. For weak absorption, dN/dz toward bright quasars is ~ 25% higher than toward faint quasars (10 sigma at low redshift, 0.4 <= z <= 1.4, and 4 sigma at high redshift, 1.4 < z <= 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being ~ 20% higher than toward bright quasars (also 10 sigma at low redshift and 4 sigma at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  4. A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

    CERN Document Server

    Wu, Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P; Gronwall, Caryl; Wesolowski, Sarah; Porterfield, Blair L

    2012-01-01

    We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about 0.3 dex to the quasar luminosity. We re-visit the alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared to studies that use non-simultaneous UV/opt...

  5. Evidence for the Thermal Sunyaev-Zel'dovich Effect Associated with Quasar Feedback

    Science.gov (United States)

    Crichton, Devin T.; Gralla, Megan B.; Hall, Kirsten; Marriage, Tobias; Zakamska, Nadia L.; Atacama Cosmology Telescope Collaboration

    2016-06-01

    Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalog, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-SPIRE data. We constrain the form of the far-infrared emission and find 3–4σ evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of (1 ‑ 5) × 1012h‑1M⊙ that these systems are expected to occupy. Modeling this signal as energy injection due to quasar feedback, our measurements are found to be consistent with a scenario in which quasars deposit up to (14.5±3.3) τ8‑1 per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is τ8 × 108 years.

  6. AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun, E-mail: ssy@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2015-04-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., α{sub ν12} (1000 ∼ 2000 Å) and α{sub ν24} (2000 ∼ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher α{sub ν}) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both α{sub ν12} and α{sub ν24} show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed α{sub ν} − z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσ{sub v} ∼ 10{sup −5}h Mpc{sup −1} at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed.

  7. An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?

    Science.gov (United States)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun

    2015-04-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., αν12 (1000 ˜ 2000 Å) and αν24 (2000 ˜ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher αν) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both αν12 and αν24 show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed αν - z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσv ˜ 10-5h Mpc-1 at z effect have also been discussed.

  8. Quasar host environments: The view from Planck

    Science.gov (United States)

    Verdier, Loïc; Melin, Jean-Baptiste; Bartlett, James G.; Magneville, Christophe; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2016-04-01

    We measure the far-infrared emission of the general quasar (QSO) population using Planck observations of the Baryon Oscillation Spectroscopic Survey QSO sample. By applying multi-component matched multi-filters to the seven highest Planck frequencies, we extract the amplitudes of dust, synchrotron, and thermal Sunyaev-Zeldovich (SZ) signals for nearly 300 000 QSOs over the redshift range 0.1 radio-quiet subsample does not show any synchrotron emission, but we detect thermal SZ between z = 2.5 and 4; no significant SZ emission is seen at lower redshifts. Depending on the supposed mass for the halos hosting the QSOs, this may or may not leave room for heating of the halo gas by feedback from the QSO.

  9. Quasar Host Environments: The view from Planck

    CERN Document Server

    Verdier, Loïc; Bartlett, James G; Magneville, Christophe; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2015-01-01

    We measure the far-infrared emission of the general quasar (QSO) population using Planck observations of the Baryon Oscillation Spectroscopic Survey QSO sample. By applying multi-component matched multi-filters to the seven highest Planck frequencies, we extract the amplitudes of dust, synchrotron and thermal Sunyaev-Zeldovich (SZ) signals for nearly 300,000 QSOs over the redshift range $0.1radio-quiet subsample does not show any synchrotron emission, but we detect th...

  10. Near-infrared imaging of the host galaxies of three radio-loud quasars at z = 1.5

    CERN Document Server

    Falomo, R; Treves, A; Falomo, Renato; Kotilainen, Jari; Treves, Aldo

    2000-01-01

    We present high spatial resolution near-infrared H-band (1.65 microns) images, taken with ISAAC on UT1 of ESO VLT, of three radio-loud quasars at z = 1.5, as a pilot study for imaging of a larger sample of radio-loud and radio-quiet quasars in the redshift range 1 < z < 2. We are able to clearly detect the host galaxy in two quasars (PKS 0000-177 and PKS 0348-120) and marginally in the third (PKS 0402-362). The host galaxies appear compact (average bulge scale-length R(e) = 4 kpc) and luminous (average M(H) = -27.6+-0.1). They are 2.5 mag more luminous than the typical galaxy luminosity (M*(H) = -25.0+-0.2), and are comparable to the hosts of low redshift radio-loud quasars (M(H) = -26), taking into account passive stellar evolution. Their luminosities are also similar to those of high redshift radio galaxies. All three quasars have at least one close companion galaxy at a projected distance < 50 kpc from the quasar, assuming they are at the same redshift.

  11. Dusty Quasars

    CERN Document Server

    Krawczyk, Coleman M; Gallagher, S C; Leighly, Karen M; Hewett, Paul C; Ross, Nicholas P; Hall, P B

    2014-01-01

    We explore the extinction/reddening of ~35,000 uniformly-selected quasars with 00.1 and 0.1% (1.3%) with E(B-V)>0.2. Simulations show both populations of quasars are intrinsically bluer than the mean composite, with a mean spectral index (${\\alpha}_{\\lambda}$) of -1.79 (-1.83). The emission and absorption-line properties of both samples reveal that quasars with intrinsically red continua have narrower Balmer lines and stronger ionizing spectral lines, the latter indicating a harder continuum in the extreme-UV and the former indicating either smaller BH mass or more face-on orientation.

  12. Spectral Variability in Hard X-rays and the Evidence for a 13.5 Years Period in the Bright Quasar 3C273

    Indian Academy of Sciences (India)

    R. K. Manchanda

    2002-09-01

    We report the observation of nearest quasar 3C273 made with LASE instrument on November 20th, 1998 as a part of our continuing programme of balloon borne hard X-ray observations in the 20–200 keV band using high sensitivity Large Area Scintillation counter Experiment. Our data clearly show a steep spectrum in the 20–200 keV with power law spectral index = 226 ± 0.07. This is in complete contrast to the reported data from OSSE and BeppoSAX which suggest the value of 1.3 to 1.6 for the power law index in the X-ray energy band, but is quite consistent with the value derived for the high energy gamma ray data. A single power law fit in the X-ray and gamma ray energy bands points to a common origin of these photons and the absence of spectral break around 1 MeV as suggested in literature. We have reanalyzed the available data to study the temporal variability of the spectrum in the hard X-ray band. Our analysis reveals that 50 keV flux from the source, shows a strong modulation with a period of about 13.5 years. The analysis of the optical light curve of the source also supports the 5000 day period.We discuss the emission mechanism and the possible sites for X-ray photons along with the implications of the long term periodicity with respect to source geometry.

  13. X-ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminous z>4 Quasars with Chandra

    CERN Document Server

    Vignali, C; Schneider, D P; Kaspi, S

    2005-01-01

    We report on Chandra observations of a sample of 11 optically luminous (Mb4 quasars known and hence represent ideal witnesses of the end of the "dark age ''. Nine quasars are detected by Chandra, with ~2-57 counts in the observed 0.5-8 keV band. These detections increase the number of X-ray detected AGN at z>4 to ~90; overall, Chandra has detected ~85% of the high-redshift quasars observed with snapshot (few kilosecond) observations. PSS 1506+5220, one of the two X-ray undetected quasars, displays a number of notable features in its rest-frame ultraviolet spectrum, the most prominent being broad, deep SiIV and CIV absorption lines. The average optical-to-X-ray spectral index for the present sample (=-1.88+/-0.05) is steeper than that typically found for z>4 quasars but consistent with the expected value from the known dependence of this spectral index on quasar luminosity. We present joint X-ray spectral fitting for a sample of 48 radio-quiet quasars in the redshift range 3.99-6.28 for which Chandra observati...

  14. Broadband nuclear emission in two radio-loud BAL quasars

    CERN Document Server

    Kunert-Bajraszewska, M; Janiuk, A

    2014-01-01

    The X-ray weakness of broad absorption line (BAL) quasars in comparison to non-BAL objects is possibly caused by the absorption of X-ray emission by the shielding material near the equatorial plane. On the other hand, the radio-loud BALQSOs are more X-ray loud than the radio-quiet ones. This suggests that part of the X-ray emission may arise from the radio jet. To investigate this possibility, we modelled the nuclear spectra of two radio-loud BALQSOs. We focus on the emission from the very centres of these two objects. The source of emission was approximated by a single, homogeneous component that produces synchrotron and inverse-Compton (IC) radiation. The simplicity of the model allowed us to estimate the basic physical parameters of the emitting regions, using a universal analytic approach. Such methods have already been used in blazars. For the first time we propose this solution for quasars. In addition, we modelled the radiation spectra of the accretion disk and its corona to compare them with the jets'...

  15. SDSS J1254+0846: A Binary Quasar Caught in the Act of Merging

    CERN Document Server

    Green, Paul J; Barkhouse, Wayne A; Mulchaey, John S; Bennert, Vardha N; Cox, Thomas J; Aldcroft, Thomas L

    2010-01-01

    We present the first luminous, spatially resolved binary quasar that clearly inhabits an ongoing galaxy merger. SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1 (SDSS J1254+0846 hereafter) are two luminous z=0.44 radio quiet quasars, with a radial velocity difference of just 215 km/s, separated on the sky by 21 kpc in a disturbed host galaxy merger showing obvious tidal tails. The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry. We present follow-up optical imaging which shows broad, symmetrical tidal arm features spanning some 75 kpc at the quasars' redshift. Numerical modeling suggests that the system consists of two massive disk galaxies prograde to their mutual orbit, caught during the first passage of an active merger. This demonstrates rapid black hole growth during the early stages of a merger between galaxies with pre-existing bulges. Neither of the two luminous nuclei show significant instrinsic absorptio...

  16. Evidence for the Thermal Sunyaev-Zel'dovich Effect Associated with Quasar Feedback

    CERN Document Server

    Crichton, Devin; Hall, Kirsten; Marriage, Tobias A; Zakamska, Nadia L; Battaglia, Nick; Bond, J Richard; Devlin, Mark J; Hill, J Colin; Hilton, Matt; Hincks, Adam D; Huffenberger, Kevin M; Hughes, John P; Kosowsky, Arthur; Moodley, Kavilan; Niemack, Michael D; Page, Lyman A; Partridge, Bruce; Sievers, Jonathan L; Sifon, Cristobal; Staggs, Suzanne T; Viero, Marco P; Wollack, Edward J

    2015-01-01

    Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalog, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy densities via a stacking analysis of Atacama Cosmology Telescope and Herschel-SPIRE data. We constrain the form and evolution of the far-infrared emission finding 3-4$\\sigma$ evidence for the presence of the thermal Sunyaev-Zel'dovich (SZ) effect in the millimetre bands. We find this signal to be characteristic of a hot ionized gas component with thermal energy $(6.2 \\pm 1.7) \\times 10^{60}$erg. This amount of thermal energy is an order of magnitude greater than would be expected assuming only hot gas in virial equilibrium with the dark matter haloes of $(1-5)\\times 10^{12}h^{-1}$M$_\\odot$ that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. We find that our measurements are consistent with a scenario in which quasars depo...

  17. The Extreme Ultraviolet Deficit and Magnetically Arrested Accretion in Radio Loud Quasars

    CERN Document Server

    Punsly, Brian

    2014-01-01

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet (EUV) for the radio loud component of the quasar population (RLQs), compared to the radio quiet component of the quasar population (RQQs). The composite quasar continuum emission between 1100 \\AA\\, and $\\sim$580 \\AA\\, is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 \\AA\\, and 580 \\AA\\, in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. da...

  18. THE EXTREME ULTRAVIOLET DEFICIT AND MAGNETICALLY ARRESTED ACCRETION IN RADIO-LOUD QUASARS

    International Nuclear Information System (INIS)

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet for the radio-loud component of the quasar population (RLQs) compared to the radio-quiet component of the quasar population. The composite quasar continuum emission between 1100 Å and ∼580 Å is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 Å and 580 Å in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large-scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. data and the numerical simulations of accretion flows in Penna et al., the magnetic islands are concentrated between the event horizon and an outer boundary of <2.8 M (in geometrized units) for rapidly rotating black holes and <5.5 M for modestly rotating black holes

  19. THE EXTREME ULTRAVIOLET DEFICIT AND MAGNETICALLY ARRESTED ACCRETION IN RADIO-LOUD QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Punsly, Brian, E-mail: brian.punsly1@verizon.net [1415 Granvia Altamira, Palos Verdes Estates, CA 90274 (United States); ICRANet, Piazza della Repubblica, I-65100 10 Pescara (Italy)

    2014-12-20

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet for the radio-loud component of the quasar population (RLQs) compared to the radio-quiet component of the quasar population. The composite quasar continuum emission between 1100 Å and ∼580 Å is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 Å and 580 Å in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large-scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. data and the numerical simulations of accretion flows in Penna et al., the magnetic islands are concentrated between the event horizon and an outer boundary of <2.8 M (in geometrized units) for rapidly rotating black holes and <5.5 M for modestly rotating black holes.

  20. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Haiman, Zoltàn [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Jiang, Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Schneider, Donald P., E-mail: imcgreer@as.arizona.edu [Department of Astronomy and Astrophysics and the Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  1. Fermi/LAT Observations of Swift/BAT Seyfert Galaxies: On the Contribution of Radio-Quiet Active Galactic Nuclei to the Extragalactic gamma-Ray Background

    Science.gov (United States)

    Teng, Stacy H.; Mushotzky, Richard F.; Sambruna, Rita M.; Davis, David S.; Reynolds, Christopher S.

    2011-01-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R(sub X,BAT) where radio-loud objects have logR(sub X,BAT) > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be approx.2x10(exp -11) photons/sq cm/s, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the gamma-ray (1-100 GeV) luminosity of BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  2. False periodicities in quasar time-domain surveys

    OpenAIRE

    Vaughan, S.; Uttley, P.; Markowitz, A. G.; Huppenkothen, D.; Middleton, M. J.; Alston, W.N.; Scargle, J. D.; Farr, W. M.

    2016-01-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. (2015a). Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars -- powered by accretion onto a single, supermassive black hole -- usually show stochastic variability over a wide range of timescales. It...

  3. The Environments of Obscured Quasars

    Science.gov (United States)

    Jones, Kristen M.; Lacy, Mark; Nielsen, Danielle

    2016-01-01

    Supermassive Black Hole (SMBH) feedback is prescribed for driving the high-end shape of the galaxy luminosity function, clearing the circumnuclear environment during the end stages of mergers, and eventually turning off its own accretion. Yet the dominant processes and characteristics of active galactic nuclei are indistinct. Chief among this confusion is how significant the role of dust is in each galaxy. Orientation of the dusty torus is attributed to causing the differences between Sy1 and Sy2, but whether obscured quasars are found in particularly dusty host galaxies, if they exist at a different stage in the merger process (early on, before the dust is blown out), or if they are merely oriented differently than optical quasars is not yet so well distinguished. With obscured quasars now observed to make up 50% or greater of the population of quasars, the question of what causes obscuration becomes vital to address. With this in mind, I study matched samples of obscured and unobscured quasars to characterize their environments, with the intent of addressing what contribution environment has to obscuration levels. I investigate the megaparsec-scale environments of SIRTF Wide-field Infra-Red Extragalactic Survey (SWIRE) quasars at z ˜ 1-3 by cross-correlating the sample with 3.8 million galaxies from the Spitzer Extragalactic Representative Volume Survey (SERVS). Optically obscured quasars are compared to a control sample of optically-bright quasars via selection in the mid-infrared. Environments were observed at 3.6 and 4.5 μm to a depth of ≈ 2 μJy (AB = 23.1). Recent work has found diverse results in such studies, with dependence of environmental richness on both redshift and level of obscuration. I find that, within reasonable error, on average there is no distinct difference between the level of clustering for obscured and normal quasars, and that there is no dependence on redshift of this result within the range of 1.3 < z < 2.5. I compare our results

  4. Evidence for the Thermal Sunyaev Zeldovich Effect Associated with Quasar Feedback

    Science.gov (United States)

    Crichton, Devin; Gralla, Megan B.; Hall, Kirsten; Marriage, Tobias A.; Zakamska, Nadia L.; Battaglia, Nick; Bond, J. Richard; Devlin, Mark J.; Hill, J. Colin; Hilton, Matt; Hincks, Adam D.; Huffenberger, Kevin M.; Hughes, John P.; Kosowsky, Arthur; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Sievers, Jonathan L.; Sifon, Cristobal; Staggs, Suzanne T.; Viero, Marco P.; Wollack, Edward J.

    2016-01-01

    Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalogue, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We constrain the form of the far-infrared emission and find 3 sigma-4 sigma evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy (6.2 plus or minus 1.7) × 10 (exp 60) erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of (1-5) × 10(exp 12) h(exp -1) solar mass that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. Our measurements are consistent with quasars depositing up to (14.5 +/- 3.3)tau (sub 8)(exp -1) per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is tau(sub 8) x 108 yr. For high quasar host masses, approximately 10(exp 13) h(exp -1) solar mass, this percentage will be reduced. Furthermore, the uncertainty on this percentage is only statistical and additional systematic uncertainties enter at the 40 per cent level. The SEDs are dust dominated in all bands and we consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 3 sigma-4 sigma level for most models.

  5. Quasar redshifts: the intrinsic component

    Science.gov (United States)

    Hansen, Peter M.

    2016-09-01

    The large observed redshift of quasars has suggested large cosmological distances and a corresponding enormous energy output to explain the brightness or luminosity as seen at earth. Alternative or complementary sources of redshift have not been identified by the astronomical community. This study examines one possible source of additional redshift: an intrinsic component based on the plasma characteristics of high temperature and high electron density which are believed to be present.

  6. LAMOST Quasar Survey

    CERN Document Server

    Wu, Xue-Bing

    2011-01-01

    The main objective of the Chinese LAMOST spectroscopic quasar survey is to discover 0.4 million new quasars from 1 million quasar candidates brighter than the magnitude limit i=20.5 in the next 5 years. This will hopefully provide the largest quasar sample for the further studies of AGN physics and cosmology. The improved quasar selection criteria based on the UKIDSS near-IR and SDSS optical colors are presented, and their advantages in uncovering the missing quasars in the quasar 'redshift desert' are demonstrated. In addition, some recent discoveries of new quasars during the LAMOST commissioning phase are presented.

  7. Ubiquitous giant Lyman $\\alpha$ nebulae around the brightest quasars at $z\\sim3.5$ revealed with MUSE

    CERN Document Server

    Borisova, Elena; Lilly, Simon J; Marino, Raffaella A; Gallego, Sofia G; Bacon, Roland; Blaizot, Jeremy; Bouché, Nicolas; Brinchmann, Jarle; Carollo, C Marcella; Caruana, Joseph; Finley, Hayley; Herenz, Edmund C; Richard, Johan; Schaye, Joop; Straka, Lorrie A; Turner, Monica L; Urrutia, Tanya; Verhamme, Anne; Wisotzki, Lutz

    2016-01-01

    Direct Lyman a imaging of fluorescent emission from intergalactic gas at z~2 has recently revealed giant cosmological structures around luminous quasars with unexpected physical properties, e.g. the Slug Nebula (Cantalupo et al. 2014). Despite their high luminosity, the detection rate of such systems in narrow-band and spectroscopic surveys is very low, i.e. less than 10%. If intrinsic and not due to observational limitations, such a low detection frequency would encode crucial information on the distribution and properties of cold gas around quasars, their emission opening angle and duty cycle. In this study, we exploit the unique capabilities of the MUSE ESO/VLT to perform a blind survey for giant Ly $\\alpha$ nebulae around 17 of the brightest radio-quiet quasars at 3quasar is asso...

  8. Close companions to two high-redshift quasars

    CERN Document Server

    McGreer, Ian D; Strauss, Michael A; Haiman, Zoltan; Richards, Gordon T; Jiang, Linhua; Bian, Fuyan; Schneider, Donald P

    2014-01-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z=4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyman alpha emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i_AB = 23.6) located 2arcsec (11 kpc projected) from the quasar with strong Lyman alpha emission (EW_0 ~ 100Ang) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z=6.25), is included in our recent HST SNAP survey of z~6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y_AB=25) at a separation of 0.9 arcsec. The red i_775-Y_105 color of the galaxy and its proximity to the quasar (7 kpc projected if at the quasar redshift) strongly favor an associati...

  9. Weak Hard X-ray Emission from Two Broad Absorption Line Quasars Observed with NuSTAR: Compton-thick Absorption or Intrinsic X-ray Weakness?

    CERN Document Server

    Luo, B; Alexander, D M; Harrison, F A; Stern, D; Bauer, F E; Boggs, S E; Christensen, F E; Comastri, A; Craig, W W; Fabian, A C; Farrah, D; Fiore, F; Fuerst, F; Grefenstette, B W; Hailey, C J; Hickox, R; Madsen, K K; Matt, G; Ogle, P; Risaliti, G; Saez, C; Teng, S H; Walton, D J; Zhang, W W

    2013-01-01

    We present NuSTAR hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain ~400-600 hard X-ray (>10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (NH<1E24 cm^{-2}). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be NH~7E24 cm^{-2} if the weak hard X-ray emission is caused by obscuration from the shielding gas. We d...

  10. Evidence of the Dynamics of Relativistic Jet Launching in Quasars

    CERN Document Server

    Punsly, Brian

    2015-01-01

    Hubble Space Telescope (HST) spectra of the extreme ultraviolet (EUV), the optically thick emission from the innermost accretion flow onto the central supermassive black hole, indicate that RLQs tend to be EUV weak compared to the radio quiet quasars (RQQs); yet the remainder of the optically thick thermal continuum is indistinguishable. The deficit of EUV emission in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. This article is an examination of the evidence for a distribution of magnetic flux tubes in the innermost accretion flow that results in magnetically arrested accretion (MAA) and creates the EUV deficit. These same flux tubes and possibly the interior magnetic flux that they encircle are the source of the jet power as well. In the MAA scenario, islands of large scale magnetic vertical flux perforate the innermost accretion flow of RLQs. The first prediction of the theory that is supported by the HST data is t...

  11. Investigating the radio-loud phase of BAL quasars

    CERN Document Server

    Bruni, G; Pedani, M; Benn, C R; Mack, K -H; Holt, J; Montenegro-Montes, F M; Jiménez-Luján, F

    2014-01-01

    Broad Absorption Lines (BALs) are present in the spectra of ~20% of quasars (QSOs), indicating the presence of fast outflows (up to 0.2c) intercepting the observer's line of sight. Radio-Loud (RL) BAL QSOs are even more rare, being four times less common than Radio-Quiet (RQ) BAL QSOs. The reason for that is still not clear, leaving open questions about the nature of the BAL-producing outflows and their connection with the radio jet. We explored the spectroscopic characteristics of RL and RQ BAL QSOs, aiming at finding a possible explanation for the rarity of the former. We identified two samples of genuine BAL QSOs from SDSS optical spectra, one RL and one RQ, in a suitable redshift interval (2.5< z <3.5) that allowed us to observe the Mg II and H$\\beta$ emission lines in the adjacent Near-Infrared (NIR) band. We collected NIR spectra of the two samples using the Telescopio Nazionale Galileo (TNG, Canary Islands). Using relations known in the literature, we could estimate black hole mass, broad line re...

  12. Mean and extreme radio properties of quasars and the origin of radio emission

    Energy Technology Data Exchange (ETDEWEB)

    Kratzer, Rachael M.; Richards, Gordon T. [Department of Physics, Drexel University, Philadelphia, PA (United States)

    2015-02-01

    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  13. The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7

    CERN Document Server

    Jiang, Linhua; Fan, Xiaohui; Strauss, Michael A; Banados, Eduardo; Becker, Robert H; Bian, Fuyan; Farnsworth, Kara; Shen, Yue; Wang, Feige; Wang, Ran; Wang, Shu; White, Richard L; Wu, Jin; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian

    2016-01-01

    We present the discovery of nine quasars at $z\\sim6$ identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of $z\\sim6$ quasars in the SDSS footprint. Our final sample consists of 52 quasars at $5.7quasars with $z_{\\rm AB}\\le20$ mag selected from 11,240 deg$^2$ of the SDSS single-epoch imaging survey (the main survey), 10 quasars with $20\\le z_{\\rm AB}\\le20.5$ selected from 4223 deg$^2$ of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to $z_{\\rm AB}\\approx22$ mag from the 277 deg$^2$ in Stripe 82. They span a wide luminosity range of $-29.0\\le M_{1450}\\le-24.5$. This well-defined sample is used to derive the quasar luminosity function (QLF) at $z\\sim6$. After combining our SDSS sample with two faint ($M_{1450}\\ge-23$ mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope $\\beta$ of the QLF is well constrained to be $\\beta=-2.8\\pm0.2$. Due to the...

  14. THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Jiang Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Ross, Nicholas P.; White, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Schneider, Donald P.; Brandt, W. Niel [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); DeGraf, Colin [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Glikman, Eilat [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Ge Jian [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Streblyanska, Alina, E-mail: imcgreer@as.arizona.edu [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)

    2013-05-10

    We present a measurement of the Type I quasar luminosity function at z = 5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M{sub 1450} < -26) with Sloan Digital Sky Survey (SDSS) data covering {approx}6000 deg{sup 2}, then extend to lower luminosities (M{sub 1450} < -24) with newly discovered, faint z {approx} 5 quasars selected from 235 deg{sup 2} of deep, coadded imaging in the SDSS Stripe 82 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7 < z < 5.1 quasars that is highly complete, with 73 spectroscopic identifications out of 92 candidates. Our color selection method is also highly efficient: of the 73 spectra obtained, 71 are high-redshift quasars. These observations reach below the break in the luminosity function (M{sub 1450}{sup *}{approx}-27). The bright-end slope is steep ({beta} {approx}< -4), with a constraint of {beta} < -3.1 at 95% confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of {approx}2 greater decrease in the number density of luminous quasars (M{sub 1450} < -26) from z = 5 to z = 6 than from z = 4 to z = 5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate {approx}30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

  15. Accretion Disc Structure and Orientation in the Lensed and Microlensed Q0957+561 Quasar

    CERN Document Server

    Schild, R E

    2005-01-01

    Because quasars are unresolved in optical imaging, their structures must presently be inferred. Gravitational microlensing offers the possibility to produce information about the luminous structure provided the Einstein ring diameter of the microlensing particle is comparable to or smaller than the radiating quasar components. The long brightness history measured for the Q0957 quasar has been analyzed previously for information about the microlensing particles, and evidence for the existence of a cosmologically significant population of planetary mass particles has been reported. The microlensing results have also directly determined the sizes of the ultraviolet light emitting surfaces in the quasar Autocorrelation analysis of the same brightness record has produced evidence for complex structure in the quasar; if the quasar suddenly brightens today, it is probable that it will brighten again after 129, 190, 540, and 620 days. We interpret these lags as the result of luminous structure around the quasar, and ...

  16. Discovery of the disturbed radio morphology in the interacting binary quasar FIRST J164311.3+315618

    CERN Document Server

    Kunert-Bajraszewska, Magdalena

    2011-01-01

    We report the high resolution radio observations and their analysis of a radio-loud compact steep spectrum (CSS) quasar FIRST J164311.3+315618, one of the members of a binary system. The second component of the system is a radio-quiet AGN. The projected separation of this pair is 2.3 arcsec (15 kpc) and it is one of the known smallest separation binary quasars. The multi-band images of this binary system made with the Hubble Space Telescope showed that the host galaxy of the radio-loud quasar is highly disturbed. The radio observations presented here were made with the multi-element radio linked interferometer network (MERLIN) at 1.66 GHz and 5 GHz. We show that the radio morphology of FIRST J164311.3+315618 is complex on both frequencies and exhibits four components, which indicate on the intermittent activity with a possible rapid change of the jet direction and/or restart of the jet due to the interaction with the companion. The radio components that are no longer powered by the jet can quickly fade away. ...

  17. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo [Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 (Japan); Willott, Chris J. [Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Im, Myungshin [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-rho, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Hibon, Pascale, E-mail: n.kashikawa@nao.ac.jp [Gemini Observatory, La Serena (Chile)

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.

  18. The race between stars and quasars in reionizing cosmic hydrogen

    International Nuclear Information System (INIS)

    The cosmological background of ionizing radiation has been dominated by quasars once the Universe aged by ∼ 2 billion years. At earlier times (redshifts z ∼> 3), the observed abundance of bright quasars declines sharply, implying that cosmic hydrogen was reionized by stars instead. Here, we explain the physical origin of the transition between the dominance of stars and quasars as a generic feature of structure formation in the concordance ΛCDM cosmology. At early times, the fraction of baryons in galaxies grows faster than the maximum (Eddington-limited) growth rate possible for quasars. As a result, quasars were not able to catch up with the rapid early growth of stellar mass in their host galaxies

  19. Data Mining for Gravitationally Lensed Quasars

    CERN Document Server

    Agnello, Adriano; Treu, Tommaso; Marshall, Philip J

    2014-01-01

    Gravitationally lensed (GL) quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine learning techniques and demonstrate that a two step strategy can be highly effective. In the first step we use catalog-level information ($griz$+WISE magnitudes, second moments) to preselect targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (Gradient-Boosted Trees), to form a final set of cand...

  20. Microlensing variability in time-delay quasars

    CERN Document Server

    Paraficz, D; Burud, I; Jakobsson, P; Eliasdottir, A

    2006-01-01

    We have searched for microlensing variability in the light curves of five gravitationally lensed quasars with well-determined time delays: SBS 1520+530, FBQ 0951+2635, RX J0911+0551, B1600+434 and HE 2149-2745. By comparing the light curve of the leading image with a suitably time offset light curve of a trailing image we find that two (SBS 1520+530 and FBQ 0951+2635) out of the five quasars have significant long-term (years) and short-term (100 days) brightness variations that may be attributed to microlensing.The short-term variations may be due to nanolenses, relativistic hot or cold spots in the quasar accretion disks, or coherent microlensing at large optical depth.

  1. Kinematics of the ionized gas around the quasar MR 2251-178

    NARCIS (Netherlands)

    Mulder, P.S.; Valentijn, E. A.

    1992-01-01

    O III forbidden line observations of the nearby quasar MR 2251-178 were made with the Taurus II imaging Fabry-Perot instrument. The line emission around the quasar is found to consist of several regions of high surface brightness located in two half-cones with an opening angle of about 37 deg extend

  2. Are there Radio-quiet Solar Flares?

    OpenAIRE

    Benz, Arnold O.; Brajsa, Roman; Magdalenic, Jasmina

    2007-01-01

    Some 15% of solar flares having a soft X-ray flux above GOES class C5 are reported to lack coherent radio emission in the 100 - 4000 MHz range (type I - V and decimetric emissions). A detailed study of 29 such events reveals that 22 (76%) of them occurred at a radial distance of more than 800'' from the disk center, indicating that radio waves from the limb may be completely absorbed in some flares. The remaining seven events have statistically significant trends to be weak in GOES class and ...

  3. A QUASAR CATALOG WITH SIMULTANEOUS UV, OPTICAL, AND X-RAY OBSERVATIONS BY SWIFT

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Porterfield, Blair L. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Vanden Berk, Daniel; Wesolowski, Sarah, E-mail: jwu@astro.psu.edu [Department of Physics, Saint Vincent College, 300 Fraser Purchase Road, Latrobe, PA 15650 (United States)

    2012-08-01

    We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is {approx}60% which rises to {approx}85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about {approx}0.3 dex to the quasar luminosity. We re-visit the {alpha}{sub ox}-L{sub 2500A} relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L{sub bol}/L{sub Edd} and {alpha}{sub UV}. We do not find significant correlations between {alpha}{sub x} and {alpha}{sub ox}, {alpha}{sub ox} and {alpha}{sub UV}, and {alpha}{sub x} and log L(0.3-10 keV). The correlations between {alpha}{sub UV} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub UV}, L{sub bol}/L{sub Edd} and {alpha}{sub x}, and L{sub bol}/L{sub Edd} and {alpha}{sub ox} are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

  4. Dust Reddening in SDSS Quasars

    CERN Document Server

    Hopkins, P F; Hall, P B; Richards, G T; Cooper, A S; Schneider, D P; Vanden Berk, Daniel E; Jester, S; Brinkmann, J; Szokoly, G P; Hopkins, Philip F.; Strauss, Michael A.; Hall, Patrick B.; Richards, Gordon T.; Cooper, Ariana S.; Schneider, Donald P.; Berk, Daniel E. Vanden; Jester, Sebastian; Szokoly, Gyula P.

    2004-01-01

    We explore the form of extragalactic reddening toward quasars using a sample of 9566 quasars with redshifts 0 0.1; less than 1% have E_{B-V} > 0.2, where the extinction is relative to quasars with modal colors. Reddening is uncorrelated with the presence of intervening narrow-line absorption systems, but reddened quasars are much more likely to show narrow absorption at the redshift of the quasar than are unreddened quasars. Thus the reddening towards quasars is dominated by SMC-like dust at the quasar redshift.

  5. Finding the Most Distant Quasars Using Bayesian Selection Methods

    CERN Document Server

    Mortlock, Daniel

    2014-01-01

    Quasars, the brightly glowing disks of material that can form around the super-massive black holes at the centres of large galaxies, are amongst the most luminous astronomical objects known and so can be seen at great distances. The most distant known quasars are seen as they were when the Universe was less than a billion years old (i.e., $\\sim\\!7%$ of its current age). Such distant quasars are, however, very rare, and so are difficult to distinguish from the billions of other comparably-bright sources in the night sky. In searching for the most distant quasars in a recent astronomical sky survey (the UKIRT Infrared Deep Sky Survey, UKIDSS), there were $\\sim\\!10^3$ apparently plausible candidates for each expected quasar, far too many to reobserve with other telescopes. The solution to this problem was to apply Bayesian model comparison, making models of the quasar population and the dominant contaminating population (Galactic stars) to utilise the information content in the survey measurements. The result wa...

  6. False periodicities in quasar time-domain surveys

    CERN Document Server

    Vaughan, S; Markowitz, A G; Huppenkothen, D; Middleton, M J; Alston, W N; Scargle, J D; Farr, W M

    2016-01-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. (2015a). Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars -- powered by accretion onto a single, supermassive black hole -- usually show stochastic variability over a wide range of timescales. It is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. Using a Bayesian analysis of the light curve of PG 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variations. We then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate ...

  7. Blowin' in the wind: both `negative' and `positive' feedback in an obscured high-z Quasar

    CERN Document Server

    Cresci, G; Brusa, M; Marconi, A; Perna, M; Mannucci, F; Piconcelli, E; Maiolino, R; Feruglio, C; Fiore, F; Bongiorno, A; Lanzuisi, G; Merloni, A; Schramm, M; Silverman, J D; Civano, F

    2014-01-01

    Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to over-grow and producing the red colors of ellipticals. On the other hand, some models are also requiring `positive' AGN feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively-driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z=1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km/s) and extended (up to 13 kpc from the black hole) outflow in the [OIII] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Ha emission and the re...

  8. Radio structure in quasars

    International Nuclear Information System (INIS)

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  9. The density structure around quasars inferred from optical depth statistics

    CERN Document Server

    Rollinde, E; Theuns, T; Petitjean, P; Chand, H

    2005-01-01

    We present a method for studying the proximity effect and use it to investigate the density structure around QSOs. It is based on the pixel optical depth probability distribution and its redshift evolution. We validate the method using mock spectra obtained from hydrodynamical simulations, and then apply it to a sample of 12 bright quasars at redshifts 2-3 observed with UVES at the VLT-UT2 Kueyen ESO telescope. These quasars do not show signatures of associated absorption and have a mean monochromatic luminosity of 5.4 10^31 ergs/s/Hz/h^2 at the Lyman limit. The distribution of optical depths changes considerably when the proper distance to the QSO is less than 10 Mpc/h. The size of this proximity region is small given that these QSOs are very bright, which suggests that the quasars are located in regions that are overdense by factors 2-10 on scales <= 10 Mpc/h.

  10. COLD FLOWS AND THE FIRST QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Di Matteo, T.; Khandai, N.; DeGraf, C.; Feng, Y.; Croft, R. A. C. [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Lopez, J. [Computer Science Department, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Springel, V. [Heidelberg Institute for Theoretical Studies Schloss-Wolfsbrunnenweg 35, 68118 Heidelberg (Germany)

    2012-02-15

    Observations of the most distant bright quasars imply that billion solar mass supermassive black holes (SMBHs) have to be assembled within the first 800 million years. Under our standard galaxy formation scenario such fast growth implies large gas densities providing sustained accretion at critical or supercritical rates onto an initial black hole seed. It has been a long standing question whether and how such high black hole accretion rates can be achieved and sustained at the centers of early galaxies. Here we use our new MassiveBlack cosmological hydrodynamic simulation covering a volume (0.75 Gpc){sup 3} appropriate for studying the rare first quasars to show that steady high density cold gas flows responsible for assembling the first galaxies produce the high gas densities that lead to sustained critical accretion rates and hence rapid growth commensurate with the existence of {approx}10{sup 9} M{sub Sun} black holes as early as z {approx} 7. We find that under these conditions quasar feedback is not effective at stopping the cold gas from penetrating the central regions and hence cannot quench the accretion until the host galaxy reaches M{sub halo} > or approx. 10{sup 1}2{sup M}{sub Sun }. This cold-flow-driven scenario for the formation of quasars implies that they should be ubiquitous in galaxies in the early universe and that major (proto)galaxy mergers are not a requirement for efficient fuel supply and growth, particularly for the earliest SMBHs.

  11. THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH. II. STATISTICAL LENS SAMPLE FROM THETHIRD DATA RELEASE

    Energy Technology Data Exchange (ETDEWEB)

    Inada, N; Oguri, M; Becker, R H; Shin, M; Richards, G T; Hennawi, J F; White, R L; Pindor, B; Strauss, M A; Kochanek, C S; Johnston, D E; Gregg, M D; Kayo, I; Eisenstein, D; Hall, P B; Castander, F J; Clocchiatti, A; Chiu, K; Kawano, Y; Scranton, R; Frieman, J; Keeton, C R; Morokuma, T; Rix, H; Turner, E L; Burless, S; Brunner, R J; Sheldon, E S; Bahcall, N A; Fukugita, M

    2007-09-13

    We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 ({approx}4188 deg{sup 2}), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1-inch and 20-inch and flux ratios of faint to bright lensed images larger than 10{sup -0.5}. We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations ({approx} 1-inch - 2-inch) and one is a large separation (15-inch) system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample.

  12. Extragalactic Extinction Laws and Quasar Structure from Color differences Between Images of Lensed Quasars

    Science.gov (United States)

    Mediavilla, Evencio

    2011-11-01

    The action of the mean gravitational field of an intervening galaxy sufficiently aligned with a distant quasar can form several images of this object (multiple imaged quasar). Random fluctuations of the gravitational field induced by the highly inhomogeneous granulation of stars or in dark matter clumps of the lens galaxy mass distribution can subdivide the images in scales of microarcsecs (microlensing by stars) or miliarcsecs (mililensing by dark matter clumps). Anomalies induced by microlensing in the flux brightness of the images can be very strong for small sources or be averaged out by sufficiently large sources. Thus, microlensing magnification of the flux of a radially stratified source can be wavelength dependent (chromaticity). On the other hand, in their path through the lens galaxy the photons of the quasar images are also affected by the patchily distributed interstellar medium (dust extinction). Thus, the wavelength dependence of extinction can be obtained from the flux ratios between two images. In this work we review the use of quasar spectra to disentangle microlensing and dust extinction (based in the comparison between the continuum and emission line flux ratios for different images of the quasar) discussing the impact of the intrinsic source variability in this procedure. We will also review some results derived using this technique like the low fraction of mass in MACHOS in the dark halos of lens galaxies, the unexpected large sizes of the accretion disks present in the central region of lensed quasars or the derivation of extinction curves in the extragalactic domain that reveals a variability in dust properties similar to the one found in the Local Group of galaxies.

  13. Photometric classification of quasars from RCS-2 using Random Forest

    Science.gov (United States)

    Carrasco, D.; Barrientos, L. F.; Pichara, K.; Anguita, T.; Murphy, D. N. A.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.; Hsieh, B. C.; López, S.

    2015-12-01

    The classification and identification of quasars is fundamental to many astronomical research areas. Given the large volume of photometric survey data available in the near future, automated methods for doing so are required. In this article, we present a new quasar candidate catalog from the Red-Sequence Cluster Survey 2 (RCS-2), identified solely from photometric information using an automated algorithm suitable for large surveys. The algorithm performance is tested using a well-defined SDSS spectroscopic sample of quasars and stars. The Random Forest algorithm constructs the catalog from RCS-2 point sources using SDSS spectroscopically-confirmed stars and quasars. The algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colors. Exploiting NUV GALEX measurements for a subset of the objects, we refine the classifier by adding new information. An additional subset of the data with WISE W1 and W2 bands is also studied. Upon analyzing 542 897 RCS-2 point sources, the algorithm identified 21 501 quasar candidates with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 89.5% and recall (the fraction of true positives relative to all sources that actually are quasars) of 88.4%. These performance metrics improve for the GALEX subset: 6529 quasar candidates are identified from 16 898 sources, with a precision and recall of 97.0% and 97.5%, respectively. Algorithm performance is further improved when WISE data are included, with precision and recall increasing to 99.3% and 99.1%, respectively, for 21 834 quasar candidates from 242 902 sources. We compiled our final catalog (38 257) by merging these samples and removing duplicates. An observational follow up of 17 bright (r < 19) candidates with long-slit spectroscopy at DuPont telescope (LCO) yields 14 confirmed quasars. The results signal encouraging progress in the classification of point sources with Random Forest algorithms to search

  14. Quasars and H II regions during reionization

    Science.gov (United States)

    Kramer, Roban Hultman

    The reionization history of the intergalactic medium (IGM) at high redshift (z ≳ 6) is just beginning to be probed by observational astronomy. In this dissertation, I discuss three projects related to the epoch of reionization. The first project explores how the evolution of the IGM neutral fraction was likely shaped by feedback processes. Because the earliest ionizing sources formed at the locations of the rare density peaks, their spatial distribution was strongly clustered. By building a semi-analytical model which includes feedback and clustering simultaneously and applying this model to the suppression of star formation in minihalos due to photoionization, I demonstrate that this clustering significantly boosts the impact of feedback processes operating at high redshift. The second project exploits the fact that high-redshift quasars drive ionization fronts (I-fronts) into the IGM, with the thickness of the front generally increasing with the hardness of the ionizing spectrum. If the thickness of the front can be measured, it can provide a novel constraint on the ionizing spectral energy distribution (SED). I simulate the propagation of an I-front into a uniform IGM, and compute its thickness for a range of possible quasar spectra and ages, and IGM neutral hydrogen densities and clumping factors. With a sufficiently high intrinsic hydrogen column density obscuring the source or a sufficiently hard power-law spectrum and some obscuration, the thickness of the front exceeds ˜ 1 physical Mpc and may be measurable from the three-dimensional morphology of its redshifted 21cm signal. In the third project, I investigate one promising method for probing the tail end of reionization, through the detection and characterization of the Gunn-Peterson damping wing absorption of the IGM in bright quasar spectra. However, the use of quasar spectra to measure the IGM damping wing requires a model of the quasar's intrinsic Lyman-alpha emission line. I quantify uncertainties

  15. Towards a comprehensive picture of powerful quasars, their host galaxies and quasar winds at z ~ 0.5

    CERN Document Server

    Wylezalek, Dominika; Liu, Guilin; Obied, Georges

    2016-01-01

    Luminous type-2 quasars in which the glow from the central black hole is obscured by dust are ideal targets for studying their host galaxies and the quasars' effect on galaxy evolution. Such feedback appears ubiquitous in luminous obscured quasars where high velocity ionized nebulae have been found. We present rest-frame yellow-band (~5000 Angstroms) observations using the Hubble Space Telescope for a sample of 20 luminous quasar host galaxies at 0.2 < z < 0.6 selected from the Sloan Digital Sky Survey. For the first time, we combine host galaxy observations with geometric measurements of quasar illumination using blue-band HST observations and [OIII] integral field unit observations probing the quasar winds. The HST images reveal bright merger signatures in about half the galaxies; a significantly higher fraction than in comparison inactive ellipticals. We show that the host galaxies are primarily bulge-dominated, with masses close to M*, but belong to < 30% of elliptical galaxies that are highly st...

  16. The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three

    CERN Document Server

    Richards, G T; Barentine, J C; Brewington, H J; Brinkmann, J; Brunner, R J; Fukugita, M; Gray, J; Gunn, J E; Hall, P B; Harvanek, M; Ivezic, Z; Jester, S; Kent, S M; Kirkland, M E; Kleinman, S J; Knapp, G R; Krzesínski, J; Long, D C; Loveday, J; Lupton, R H; Meiksin, A; Nash, T; Neilsen, E H; Nitta, A; Pope, A; Schlegel, D J; Schneider, D P; Snedden, S A; Stoughton, C; Strauss, M A; Szalay, A S; Thakar, A R; Vanden Berk, Daniel E; Xiaohui F; Yanny, B; York, Do G; Anderson, Scott F.; Berk, Daniel E. Vanden; Brunner, Robert J.; Fan, Xiaohui; Gray, Jim; Gunn, James E.; Hall, Patrick B.; Ivezic, Zeljko; Jester, Sebastian; Kirkland, Margaret E.; Loveday, Jon; Meiksin, Avery; Pope, Adrian; Richards, Gordon T.; Schneider, Donald P.; Stoughton, Chris; Strauss, Michael A.; Szalay, Alexander S.; Thakar, Anirudda R.; Yanny, Brian; York, Donald G.

    2006-01-01

    We determine the number counts and z=0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg^2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg^2 of imaging data from SDSS Data Release Three. The sample extends from i=15 to i=19.1 at z3. The number counts and luminosity function agree well with the results of the 2dF QSO Survey, but the SDSS data probe to much higher redshifts than does the 2dF sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best fit model has a flatter bright end slope at high redshift than at low redshift. For z5-sigma level, must be accounted for in models of the evolution of ...

  17. Hubble Space Telescope Images of Nearby Luminous Quasars. 2; Results for Eight Quasars and Tests of the Detection Sensitivity

    Science.gov (United States)

    Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1995-01-01

    Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for eight intrinsically luminous quasars with redshifts between 0.16 and 0.29. These observations, when combined with a similar HST study of the quasar PKS 2349-014, show that luminous nearby quasars exist in a variety of environments. Seven companion galaxies brighter than M(V) = 16.5 (H(sub 0) = 100 km s(sup -1) Mpc(sup -1), Omega(sub 0) = 1.0) lie within a projected distance of 25 kpc of the quasars; three of the companions are located closer than 3'' (6 kpc projected distance) from the quasars, well within the volume that would be enclosed by a typical L* host galaxy. The observed association of quasars and companion galaxies is statistically significant and may he an important element in the luminous-quasar phenomenon. Apparent host galaxies are detected for three of the quasars: PG 1116+215, 3C 273, and PG 1444+407; the hosts have an average absolute magnitude of about 0.6 mag brighter than L*. The agreement between the previously published major-axis directions in ground-based images and in the present HST images of 3C 273 and PG 1444+407 constitutes important evidence supporting the reality of these candidate host galaxies. Upper limits are placed on the visual-band brightnesses of representative galactic hosts for all the quasars. These limits are established by placing galaxy images obtained with HST underneath the quasars and measuring at what faintness level the known galaxies are detected. On average, the HST spirals would have been detected if they were as faint as 1 mag below L*, and the early-type galaxies could have been detected down to a brightness level of about L*, where L* is the Schechter characteristic luminosity of field galaxies. Smooth, featureless galaxy models (exponential disks or de Vaucouleurs profiles) are fitted to the residual light after a best-fitting point source is subtracted from the quasar images. The results show that smooth spiral

  18. ROSAT PSPC observations of the infrared quasar IRAS 13349+2438 evidence for a warm absorber with internal dust

    CERN Document Server

    Brandt, W N; Pounds, K A

    1995-01-01

    We present spatial, temporal and spectral analyses of ROSAT Position Sensitive Proportional Counter (PSPC) observations of the infrared loud quasar IRAS 13349+2438. IRAS 13349+2438 is the archetypal highly-polarized radio-quiet QSO and has an optical/infrared luminosity of about 2E46 erg/s. We detect variability in the ROSAT count rate by a factor of 4.1 in about one year, and there is also evidence for about 25 per cent variability within one week. We find no evidence for large intrinsic cold absorption of soft X-rays. These two facts have important consequences for the scattering-plus-transmission model of this object which was developed to explain its high wavelength-dependent polarization and other properties. The soft X-ray variability makes electron scattering of most of the soft X-rays difficult without a very peculiar scattering mirror. The lack of significant intrinsic cold X-ray absorption together with the large observed E(B-V) suggests either a very peculiar system geometry or, more probably, abso...

  19. Astrometric Redshifts for Quasars

    CERN Document Server

    Kaczmarczik, Michael C; Mehta, Sajjan S; Schlegel, David J

    2009-01-01

    The wavelength dependence of atmospheric refraction causes differential chromatic refraction (DCR), whereby objects imaged at different optical/UV wavelengths are observed at slightly different positions in the plane of the detector. Strong spectral features induce changes in the effective wavelengths of broad-band filters that are capable of producing significant positional offsets with respect to standard DCR corrections. We examine such offsets for broad-emission-line (type 1) quasars from the Sloan Digital Sky Survey (SDSS) spanning 0quasar spectrum with the SDSS bandpasses as a function of redshift and airmass. This astrometric information can be used to break degeneracies in photometric redshifts of quasars (or other emission-line sources) and, for extreme cases, may be suitable for determining "astrometric redshifts". On the SDSS's southern equatorial stripe, where it is pos...

  20. Quasar variability limits on cosmological density of cosmic strings

    CERN Document Server

    Tuntsov, Artem

    2010-01-01

    We put robust upper limits on the average cosmological density \\Omega_s of cosmic strings based on the variability properties of a large homogeneous sample of SDSS quasars. We search for an excess of characteristic variations of quasar brightness that are associated with string lensing and use the observed distribution of this variation to constrain the density of strings. The limits obtained do not invoke any clustering of strings, apply to both open segments and closed loops of strings, usefully extend over a wide range of tensions 10^{-13} < G\\mu/c^2 < 10^{-9} and reach down the level of \\Omega_s=0.01 and below. Further progress in this direction will depend on better understanding of quasar intrinsic variability rather than a mere increase in the volume of data.

  1. Exploratory Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30

    CERN Document Server

    Ai, Yanli; Fan, Xiaohui; Wang, Feige; Wu, Xue-Bing; Bian, Fuyan

    2016-01-01

    We report exploratory \\chandra\\ observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by \\chandra\\ with a possible component of extended emission. The rest-frame 2-10 keV luminosity is 9.0$^{+9.1}_{-4.5}$ $\\times$ 10$^{45}$ erg s$^{-1}$ with inferred photon index of $\\Gamma$ = 3.03$^{+0.78}_{-0.70}$. This quasar is X-ray bright, with inferred X-ray-to-optical flux ratio \\aox\\ $=-1.22^{+0.07}_{-0.05}$, higher than the values found in other quasars of comparable ultraviolet luminosity. The properties inferred from this exploratory observation indicate that this ultraluminous quasar might be growing with super-Eddington accretion and probably viewed with small inclination angle. Deep X-ray observation will help to probe the plausible extended emission and better constraint the spectral features for this ultraluminous quasar.

  2. Polarization structure of 12 gamma-ray quasars at 5 and 15 GHz

    Science.gov (United States)

    Vetukhnovskaya, Yu. N.; Gabuzda, D. C.

    2012-12-01

    The results of dual-frequency polarization observations of 12 gamma-ray quasars are presented (as a continuation of a study of six blazars carried out earlier). The observations were obtained with the American Very Long Baseline Array. The distributions of intensity and polarization were obtained at 5 and 15 GHz. The degrees of polarization in the cores and jets of the 18 gamma-ray quasars do not stand out from those of other quasars. The brightness temperatures of the core components do not strongly exceed 1012 K.

  3. Resolving the Structure at the Heart of BAL Quasars Through Microlensing Induced Polarisation Variability

    CERN Document Server

    Hales, C A; Hales, Christopher A.; Lewis, Geraint F.

    2007-01-01

    While amongst the most luminous objects in the universe, many details regarding the inner structure of quasars remain unknown. One such area is the mechanism promoting increased polarisation in the broad absorption line troughs of certain quasars. This study shows how microlensing can be used to differentiate between two popular models that explain such polarisation through a realistic computational analysis. By examining a statistical ensemble of correlation data between two observables (namely image brightness and polarisation of the flux coming from the quasar), it was found that through spectropolarimetric monitoring it would be possible to discern between a model with an external scattering region and a model without one.

  4. Optical Microlensing and Accretion Disk Structure in the Lensed Quasar SDSS 1520+530

    Science.gov (United States)

    Manickam, Vigneshwar; Grinaski, Ian; MacLeod, Chelsea; Morgan, Christopher W.; Harris, Hugh C.; Kennington, James

    2015-01-01

    We analyze uncorrelated variability in seven seasons of SDSS r-band monitoring data from the doubly-imaged gravitationally lensed quasar SBS 1520+530 to yield a measurement of the size of the near-UV continuum emission region in this quasar. Photometry in the SBS 1520+530 system is complicated significantly by the proximity of a very bright star whose diffraction spike blends with the the lens, so we employed a mirror-flip subtraction technique to correct for this contamination. We conclude by testing our accretion disk measurement against the Quasar Accretion Disk Size - Black Hole Mass Relation.

  5. The intrinsic quasar luminosity function: Accounting for accretion disk anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    DiPompeo, M. A.; Myers, A. D.; Brotherton, M. S. [University of Wyoming, Department of Physics and Astronomy 3905, 1000 East University, Laramie, WY 82071 (United States); Runnoe, J. C. [Penn State University, Department of Astronomy and Astrophysics, 413 Davey Lab, University Park, PA 16802 (United States); Green, R. F. [Large Binocular Telescope Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-05-20

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ∼2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

  6. Metallicity and Quasar Outflows

    CERN Document Server

    Wang, Huiyuan; Yuan, Weimin; Wang, Tinggui

    2012-01-01

    Correlations are investigated of the outflow strength of quasars, as measured by the blueshift and asymmetry index (BAI) of the CIV line (Wang et al. 2011), with intensities and ratios of broad emission lines, based on composite quasar spectra built from the Sloan Digital Sky Survey. We find that most of the line ratios of other ions to CIV prominently increases with BAI. These behaviors can be well understood in the context of increasing metallicity with BAI. The strength of dominant coolant, CIV line, decreases and weak collisionally excited lines increase with gas metallicity as a result of the competition between different line coolants. Using SiIV+OIV]/CIV as an indicator of gas metallicity, we present, for the first time, a strong correlation between the metallicitiy and the outflow strength of quasars over a wide range of 1.7 to 6.9 times solar abundance. Our result implies that the metallicity plays an important role in the formation of quasar outflows, likely via affecting outflow acceleration. This ...

  7. Quasars : The Observational Perspectives

    NARCIS (Netherlands)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Shields, Greg; Gaskell, Martin; Boroson, Todd; Laor, Ari; Hawkins, Michael; Pronik, Vladimir; Sergeev, Sergey; Dultzin, Deborah; Grupe, Dirk; Richards, Gordon; Morganti, Raffaella; Volvach, Aleksander; Zamfir, Sebastian; Falcke, Heino; Körding, Elmar; Elvis, Martin; Turner, Tracey Jane; Kembhavi, Ajit; Foschini, Luigi; Neshpor, Yuri; Franceschini, Alberto

    2012-01-01

    The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves the nomenclature that has evolved to label the multifold phenomenological manifestations now united under the umbrella of active galactic nuclei (AGNs). A further com

  8. The Hamburg Quasar Monitoring Program (HQM) at Calar Alto. I. Low amplitude variability in quasars

    OpenAIRE

    Borgeest, U.; Schramm, K. -J.

    1994-01-01

    HQM is an optical broad-band photometric monitoring program carried out since Sept.~1988. Our main intention is to search for indications of microlensing in a sample of $\\sim$\\,100 selected quasars; however, we also want to study the intrinsic variability. We use a CCD camera equipped to the MPIA 1.2$\\,$m telescope. Fully automatic photometric reduction relative to stars in the frame is done within a few minutes after each exposure, thus interesting brightness changes can be followed in detai...

  9. Cross-Correlation of SDSS DR7 Quasars and DR10 BOSS Galaxies: The Weak Luminosity Dependence of Quasar Clustering at z~0.5

    CERN Document Server

    Shen, Yue; White, Martin; Zheng, Zheng; Myers, Adam D; Guo, Hong; Kirkpatrick, Jessica A; Padmanabhan, Nikhil; Parejko, John K; Ross, Nicholas P; Schlegel, David J; Schneider, Donald P; Streblyanska, Alina; Swanson, Molly E C; Zehavi, Idit; Pan, Kaike; Bizyaev, Dmitry; Brewington, Howard; Ebelke, Garrett; Malanushenko, Viktor; Malanushenko, Elena; Oravetz, Daniel; Simmons, Audrey; Snedden, Stephanie

    2012-01-01

    We present the measurement of the two-point cross-correlation function (CCF) of 8,198 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) quasars and 349,608 DR10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey (BOSS) at redshift ~0.5 (0.3=0.53 from the CCF measurements. This linear bias corresponds to a characteristic host halo mass of ~4x10^12 M_sun/h, compared to ~10^13 M_sun/h characteristic host halo mass for CMASS galaxies. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db_Q/dlogL=0.20+-0.34 or 0.11+-0.32 (depending on different luminosity divisions) for quasar luminosities -23.5>M_i(z=2)>-25.5, implying a weak luminosity dependence of quasar clustering for the bright end of the quasar population at ~0.5. We compare our measurements with theoretical predictions, Halo Occupation Distribution (HOD) models and mock catalogs. These comparisons suggest quasars reside in a broad range of host halos, and the host halo mass distributions...

  10. Dusty Quasars at High Redshifts

    Science.gov (United States)

    Weedman, Daniel; Sargsyan, Lusine

    2016-09-01

    A population of quasars at z ˜ 2 is determined based on dust luminosities νL ν (7.8 μm) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio νL ν (0.25 μm)/νL ν (7.8 μm) = UV/IR, assumed to measure obscuration of UV luminosity by the dust that produces IR luminosity. Quasar counts at rest-frame 7.8 μm are determined for quasars in the Boötes field of the NOAO Deep Wide Field Survey using 24 μm sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far-infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high-redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest-frame 7.8 μm, but the ratio L ν (100 μm)/L ν (7.8 μm) is about three times higher for obscured quasars than for unobscured, so that far-infrared or submillimeter quasar detections are dominated by obscured quasars. We find that only ˜5% of high-redshift submillimeter sources are quasars and that existing 850 μm surveys or 2 mm surveys should already have detected sources at z ˜ 10 if quasar and starburst luminosity functions remain the same from z = 2 until z = 10.

  11. Data mining for gravitationally lensed quasars

    Science.gov (United States)

    Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.

    2015-04-01

    Gravitationally lensed quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target-selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine-learning techniques and demonstrate that a two-step strategy can be highly effective. In the first step, we use catalogue-level information (griz+WISE magnitudes, second moments) to pre-select targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (gradient-boosted trees), to form a final set of candidates. The results from this procedure can be used to further refine the simpler SQLS algorithms, with a twofold (or threefold) gain in purity and the same (or 80 per cent) completeness at target-selection stage, or a purity of 70 per cent and a completeness of 60 per cent after the candidate-selection step. Simpler photometric searches in griz+WISE based on colour cuts would provide samples with 7 per cent purity or less. Our technique is extremely fast, as a list of candidates can be obtained from a Stage III experiment (e.g. DES catalogue/data base) in a few CPU hours. The techniques are easily extendable to Stage IV experiments like LSST with the addition of time domain information.

  12. The Extended Baryon Oscillation Spectroscopic Survey: Variability Selection and Quasar Luminosity Function

    CERN Document Server

    Palanque-Delabrouille, N; Yèche, Ch; Pâris, I; Petitjean, P; Burtin, E; Dawson, K; McGreer, I; Myers, A D; Rossi, G; Schlegel, D; Schneider, D; Streblyanska, A; Tinker, J

    2015-01-01

    The SDSS-IV/eBOSS has an extensive quasar program that combines several selection methods. Among these, the photometric variability technique provides highly uniform samples, unaffected by the redshift bias of traditional optical-color selections, when $z= 2.7 - 3.5$ quasars cross the stellar locus or when host galaxy light affects quasar colors at $z 2.2$. Both models are constrained to be continuous at $z=2.2$. They present a flattening of the bright-end slope at large redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3\\% (resp., 1.1\\%) to $g<22.5$ (resp., $g<23$). The models are also in good agreement over the entire redshift range with models from previous studies.

  13. Quasars in the Cosmic Environment

    NARCIS (Netherlands)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Dultzin, Deborah; Richards, Gordon; Knapen, Johan; Shlosman, Isaac; Morganti, Raffaella; Falomo, Renato; Hawkins, Mike; Cavaliere, Alfonso; McLure, Ross; Shields, Greg; Netzer, Hagai; Proga, Daniel; Franceschini, Alberto; Fan, Xiaoui; Elvis, Martin

    2012-01-01

    We now consider the environment of quasars in the widest possible sense, from the circumnuclear regions to very large scales of hundreds of kiloparsecs. The circumgalactic environment of nearby quasars has been widely studied since the late 1960s in an attempt to test its influence on the triggering

  14. AzTEC 1.1 mm images of 16 radio galaxies at 0.5quasar at z=6.3

    CERN Document Server

    Humphrey, A; Aretxaga, I; Hughes, D H; Yun, M S; Cybulski, R; Wilson, Grant W; Austermann, J; Ezawa, H; Kawabe, R; Kohno, K; Perera, T; Scott, K; Sánchez-Arguelles, D; Gutermuth, R

    2011-01-01

    We present 1.1 mm observations for a sample of 16 powerful radio galaxies at 0.5radio quiet quasar at z=6.3, obtained using the AzTEC bolometer array mounted on the ASTE or the JCMT. This paper more than doubles the number of high-z radio galaxies imaged at millimetre/sub-millimetre wavelengths. We detect probable millimetre-wave counterparts for 11 of the active galaxies. The 6 active galaxies which do not have a probable millimetre counterpart in our images nevertheless have one or more likely associated millimetric source. Thus, we conclude that powerful (radio-loud) active galaxies at high-z are beacons for finding luminous millimetre/sub-millimetre galaxies at high-z. The flux densities of our AzTEC counterparts imply star formation rates ranging from <200 to ~1300 M./yr. In addition, we find that for the radio galaxoes the 1.1 mm flux density is anticorrelated with the largest angular size of the radio source. We also present new Spitzer imaging observations of several active galax...

  15. THE MAGELLANIC QUASARS SURVEY. III. SPECTROSCOPIC CONFIRMATION OF 758 ACTIVE GALACTIC NUCLEI BEHIND THE MAGELLANIC CLOUDS

    International Nuclear Information System (INIS)

    The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR, and/or X-ray properties. We spectroscopically confirmed 758 quasars (565 in the LMC and 193 in the SMC) behind the clouds, of which 94% (527 in the LMC and 186 in the SMC) are newly identified. The MQS quasars have long-term (12 yr and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the clouds, and 50 quasars are bright enough (I ∼< 18 mag) for absorption studies of the interstellar/intergalactic medium of the clouds

  16. Witnessing the Birth of a Quasar

    CERN Document Server

    Tanaka, Takamitsu; Menou, Kristen

    2010-01-01

    The coalescence of a supermassive black hole binary (SMBHB) is thought to be accompanied by an electromagnetic (EM) afterglow, produced by the viscous infall of the surrounding circumbinary gas disk after the merger. It has been proposed that once the merger has been detected in gravitational waves (GWs) by LISA, follow-up EM searches for this afterglow can help identify the EM counterpart of the LISA source. Here we study whether the afterglows may be sufficiently bright and numerous to be detectable in EM surveys alone. The viscous afterglow, which lasts for years to decades for SMBHBs in LISA's sensitivity window, is characterized by rapid increases in both the bolometric luminosity and in the spectral hardness of the source. If quasar activity is triggered by the same major galaxy mergers that produce SMBHBs, then the afterglow could be interpreted as a signature of the birth of a quasar. Using an idealized model for the post-merger viscous spreading of the circumbinary disk and the resulting light curve,...

  17. Microlensing as a possible probe of event-horizon structure in quasars

    CERN Document Server

    Tomozeiu, Mihai; Rabold, Manuel; Saha, Prasenjit; Wambsganss, Joachim

    2016-01-01

    In quasars which are lensed by galaxies, the point-like images sometimes show sharp and uncorrelated brightness variations (microlensing). These brightness changes are associated with the innermost region of the quasar passing through a complicated pattern of caustics produced by the stars in the lensing galaxy. In this paper, we study whether the universal properties of optical caustics could enable extraction of shape information about the central engine of quasars. We present a toy model with a crescent-shaped source crossing a fold caustic. The silhouette of a black hole over an accretion disk tends to produce roughly crescent sources. When a crescent-shaped source crosses a fold caustic, the resulting light curve is noticeably different from the case of a circular luminosity profile or Gaussian source. With good enough monitoring data, the crescent parameters, apart from one degeneracy, can be recovered.

  18. False periodicities in quasar time-domain surveys

    Science.gov (United States)

    Vaughan, S.; Uttley, P.; Markowitz, A. G.; Huppenkothen, D.; Middleton, M. J.; Alston, W. N.; Scargle, J. D.; Farr, W. M.

    2016-09-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars - powered by accretion on to a single, supermassive black hole - usually show stochastic variability over a wide range of time-scales. It is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. Using a Bayesian analysis of the light curve of PG 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variation. We then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate these points. From a few thousand simulations of steep spectrum (`red noise') stochastic processes, we find many simulations that display few-cycle periodicity like that seen in PG 1302-102. We emphasize the importance of calibrating the false positive rate when the number of targets in a search is very large.

  19. Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars

    CERN Document Server

    Prochaska, J Xavier; Lee, Khee-Gan; Cantalupo, Sebastiano; Bovy, Jo; Djorgovski, S G; Ellison, Sara L; Lau, Marie Wingyee; Martin, Crystal L; Myers, Adam; Rubin, Kate H R; Simcoe, Robert A

    2013-01-01

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the HI Lya absorption transverse to luminous, z~2 quasars at proper separations of 30kpc 17.3) at separations R<200kpc, which decreases to ~20% at R~1Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function xi_QA(r) = (r/r_0)^gamma with a large correlation length r_0 = 12.5+2.7-1.4 Mpc/h (comoving) and gamma = 1.68+0.14-0.30. The HI absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos Mhalo~10^12.5 Msun at z~2.5. The environments of these massive halos are highly biased towards producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence th...

  20. Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars

    DEFF Research Database (Denmark)

    Ganguly, Rajib; Brotherton, Michael S.; Arav, Nahum;

    2007-01-01

    We present low-resolution ultraviolet spectra of 14 low redshift (z zz 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ~ L^0.62 relation derived by Laor & Brandt (2002). Another quasa...

  1. Investigation of the angular structure of the quasar 3C196 radio emission

    International Nuclear Information System (INIS)

    The angular dimensions and spectral characteristics are determined for the components of the preferrable brightness distribution model of the quasar 3C196 at decameter and shorter wavelengths. The physical processes are discussed that might be responsible for the extended region of radio emission that has been detected in 3C196 at decameter wavelengths

  2. Far-infrared and Molecular CO Emission From the Host Galaxies of Faint Quasars at z~6

    CERN Document Server

    Wang, Ran; Carilli, Chris L; Neri, Roberto; Walter, Fabian; Omont, Alain; Riechers, Dominik A; Bertoldi, Frank; Menten, Karl M; Cox, Pierre; Strauss, Michael A; Fan, Xiaohui; Jiang, Linhua

    2011-01-01

    We present new millimeter and radio observations of nine z~6 quasars discovered in deep optical and near-infrared surveys. We observed the 250 GHz continuum in eight of the nine objects and detected three of them. New 1.4 GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250 GHz detections and detected two of them. We study the FIR and radio emission and quasar-host galaxy evolution with a sample of 18 z~6 quasars that are faint at UV/optical wavelengths (rest-frame 1450A magnitudes of m_1450\\ge20.2). The average FIR-to-AGN UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z~6 (m_1450<20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z~6 quasars, and the average luminosities of samples of submillimeter /millimeter-observed quasars at z~2 to 5, yields a relationship of L_{FIR} {L_{bol}}^{0.62}. ...

  3. The complex evolutionary paths of local infrared bright galaxies: a high angular resolution mid-infrared view

    CERN Document Server

    Alonso-Herrero, A; Roche, P F; Hernan-Caballero, A; Aretxaga, I; Martinez-Paredes, M; Almeida, C Ramos; Pereira-Santaella, M; Diaz-Santos, T; Levenson, N A; Packham, C; Colina, L; Esquej, P; Gonzalez-Martin, O; Ichikawa, K; Imanishi, M; Espinosa, J M Rodriguez; Telesco, C

    2016-01-01

    We investigate the evolutionary connection between local IR-bright galaxies ($\\log L_{\\rm IR}\\ge 11.4\\,L_\\odot$) and quasars. We use high angular resolution ($\\sim$ 0.3-0.4 arcsec $\\sim$ few hundred parsecs) $8-13\\,\\mu$m ground-based spectroscopy to disentangle the AGN mid-IR properties from those of star formation. The comparison between the nuclear $11.3\\,\\mu$m PAH feature emission and that measured with Spitzer/IRS indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or...

  4. Dusty Quasars at High Redshifts

    CERN Document Server

    Weedman, Daniel

    2016-01-01

    A population of quasars at z ~ 2 is determined based on dust luminosities vLv(7.8 um) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio vLv(0.25 um)/vLv(7.8 um) = UV/IR, assumed to measure obscuration of UV luminosity by the dust which produces IR luminosity. Quasar counts at rest frame 7.8 um are determined for quasars in the Bootes field of the NOAO Deep Wide Field Survey using 24 um sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest frame 7.8 um, but the ratio Lv(100 um)/Lv(7.8 um) is about three times high...

  5. The Road to Quasars

    CERN Document Server

    Kellermann, K I

    2014-01-01

    Although the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities. Not until the 1962 occultations of the strong radio source 3C 273 at Parkes, which led Maarten Schmidt to identify 3C 273 with an apparent stellar object at a redshift of 0.16, was the true nature understood. Successive radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts and the general, although for some decades not universal, acceptance of quasars as the very luminous nuclei of galaxies. Curiously, 3C 273, which is one of the strongest extragalactic sources in the sky, was first cataloged in 1959 and the magnitude 13 optical counterpart was observed at least as early as 1887. Since 1960, much fainter optical counterparts were being routinely identified using accurate radio inte...

  6. Quasars Probing Quasars. VI. Excess H I Absorption within One Proper Mpc of z ~ 2 Quasars

    Science.gov (United States)

    Prochaska, J. Xavier; Hennawi, Joseph F.; Lee, Khee-Gan; Cantalupo, Sebastiano; Bovy, Jo; Djorgovski, S. G.; Ellison, Sara L.; Lau, Marie Wingyee; Martin, Crystal L.; Myers, Adam; Rubin, Kate H. R.; Simcoe, Robert A.

    2013-10-01

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ~ 2 quasars at proper separations of 30 kpc line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc)-0.46. We also observe a high (sime 60%) covering factor of strong, optically thick H I absorbers (H I column N_{H\\,\\scriptsize{I}}>10^{17.3}\\, cm^{-2}) at separations R dark matter halos M halo ≈ 1012.5 M ⊙ at z ~ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ~ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  7. A Structure for Quasars

    CERN Document Server

    Elvis, Martin

    2009-01-01

    This paper proposes a simple, empirically derived, unifying structure for the inner regions of quasars. This structure is constructed to explain the broad absorption line (BAL) regions, the narrow `associated' ultraviolet and X-ray warm absorbers (NALs); and is also found to explain the broad emission line regions (BELR), and several scattering features, including a substantial fraction of the broad X-ray Iron-K emission line, and the bi-conical extended narrow emission line region (ENLR) structures seen on large kiloparsec scales in Seyfert images. Small extensions of the model to allow luminosity dependent changes in the structure may explain the UV and X-ray Baldwin effects and the greater prevalence of obscuration in low luminosity AGN.

  8. 'Round the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar

    CERN Document Server

    Colley, W N; Abajas, C; Alcalde, D; Aslan, Z; Barrena, R; Dudinov, V; Khamitov, I; Kjernsmo, K; Lee, H J; Lee, J; Lee, M G; Licandro, J; Maoz, D; Mediavilla, E; Motta, V; Muñoz, J; Oscoz, A; Serra-Ricart, M; Sinelnikov, I; Stabell, R; Teuber, J; Zheleznyak, A T; Colley, Wesley N.; Schild, Rudolph E.; Abajas, Cristina; Alcalde, David; Aslan, Zeki; Barrena, Rafael; Dudinov, Vladimir; Khamitov, Irek; Kjernsmo, Kjetil; Lee, Hyun Ju; Lee, Jonghwan; Lee, Myung Gyoon; Licandro, Javier; Maoz, Dan; Mediavilla, Evencio; Motta, Veronica; Munoz, Jose; Oscoz, Alex; Serra-Ricart, Miquel; Sinelnikov, Igor; Stabell, Rolf; Teuber, Jan; Zheleznyak, Alexander

    2001-01-01

    An observing campaign with 10 participating observatories has undertaken to monitor the optical brightness of the Q0957 gravitationally lensed quasar for 10 consecutive nights in January 2000. The resulting A image brightness curve has significant brightness fluctuations and makes a photometric prediction for the B image light curve for a second campaign planned for 12-21 March 2001. The ultimate purpose is to determine the gravitational lens time delay to a fraction of an hour, and to seek evidence for rapid microlensing.

  9. Discovery of eight z ~ 6 quasars from Pan-STARRS1

    CERN Document Server

    Bañados, E; Morganson, E; Decarli, R; Walter, F; Chambers, K C; Rix, H-W; Farina, E P; Fan, X; Jiang, L; McGreer, I; De Rosa, G; Simcoe, R; Weiß, A; Price, P A; Morgan, J S; Burgett, W S; Greiner, J; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Stubbs, C W; Sweeney, W; Tonry, J L; Wainscoat, R J; Waters, C

    2014-01-01

    High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey Telescope & Rapid Response System 1 and follow-up strategy to discover quasars in the redshift range 5.75.7 by more than 10%. We additionally recovered 18 previously known quasars. The eight quasars presented here span a large range of luminosities (-27.3 < M_{1450} < -25.4; 19.6 < z_ps1 < 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show a weak or no Ly$\\alpha$ emission line (25% with rest-frame equivalent width of the Ly$\\alpha$ + Nv line lower than 15{\\AA}). We find a larger fraction of weak-line emission quasars than in lower redshift studies. This may imply that the weak-line quasar population at the highest redshifts could be more abundant than previously thought. However,...

  10. Structure of the Seyfert galaxy NGC 1275 and the quasar 3C 345 nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Matveenko, L.I.; Paulini-Tos, I.K.; Kostenko, V.I.; Romni, Dzh.D.; Bot, L.B.

    1985-06-01

    Structure of the quasar 3C 345 and the Seyfert galaxy NGC 1275 has been studied with a global radio interference network at 18 cm wavelength. The quasar has a nucleus and a compact feature, both sizing to approximately 0.3 mas, and a fine jet, the brightness of which decreases with the distance from the nucleus, its position angle changing too. The central compact feature of NGC 1275, which has been observed at shorter wavelengths, is absent at 18 cm. This is likely due to reabsorption and absorption of synchrotron emission by the ionized gas surrounding the nucleus.

  11. Structure of the Seyfert galaxy NGC 1275 and the quasar 3C 345 nuclei

    International Nuclear Information System (INIS)

    Structure of the quasar 3C 345 and the Seyfert galaxy NGC 1275 has been studied with a global radio interference network at 18 cm wavelength. Quasar has a nucleus and a compact feature, both sizing to approximately 0.3 mas, and a fine jet, the brightness of which decreases with the distance from the nucleus, its position angle changing too. The central compact feature of NGC 1275, which has been observed at shorter wavelengths, is absent at 18 cm. This is likely due to reabsorption and absorption of synchrotron emission by the ionized gas surrounding the nucleus

  12. Cosmic evolution of Quasar radio structure

    Science.gov (United States)

    Hutchings, J. B.; Neff, S. G.

    1991-01-01

    We discuss the results of a survey of Quasar radio structures over redshifts from 0.6 to 3.7. There are clear evolutionary trends in size and luminosity, which suggest that the duty cycle of individual Quasars has increased over cosmic time. This affects source count statistics and gives clues on the evolution of Quasar environments.

  13. Quasar Structure from Microlensing in Gravitationally Lensed Quasars

    Science.gov (United States)

    Morgan, Christopher W.

    2007-12-01

    I investigate microlensing in gravitationally lensed quasars and discuss the use of its signal to probe quasar structure on small angular scales. I describe our lensed quasar optical monitoring program and RETROCAM, the optical camera I built for the 2.4m Hiltner telescope to monitor lensed quasars. I use the microlensing variability observed in 11 gravitationally lensed quasars to show that the accretion disk size at 2500Å is related to the black hole mass by log(R2500/cm) = (15.70±0.16) + (0.64±0.18)log(MBH/109M⊙). This scaling is consistent with the expectation from thin disk theory (R ∝ MBH2/3), but it implies that black holes radiate with relatively low efficiency, log(η) = -1.54±0.36 + log(L/LE) where η=L/(Mdotc2). With one exception, these sizes are larger by a factor of 4 than the size needed to produce the observed 0.8µm quasar flux by thermal radiation from a thin disk with the same T ∝ R-3/4 temperature profile. More sophisticated disk models are clearly required, particularly as our continuing observations improve the precision of the measurements and yield estimates of the scaling with wavelength and accretion rate. This research made extensive use of a Beowulf computer cluster obtained through the Cluster Ohio program of the Ohio Supercomputer Center. Support for program HST-GO-9744 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26666.

  14. On the nature of the "radio quiet" black hole binaries

    OpenAIRE

    Soleri, Paolo; Fender, Rob

    2011-01-01

    The coupling between accretion processes and ejection mechanisms in accreting black holes in binary systems can be investigated by empirical relations between the X-ray/radio and X-ray/optical-infrared luminosities. These correlations are valid over several orders of magnitude and were initially thought to be universal. However, recently, many black hole binaries have been found to produce jets that, given certain accretion-powered luminosities, are fainter than expected from the earlier corr...

  15. Cygnus X-2 in a radio quiet state

    Science.gov (United States)

    Rushton, A.; Bach, U.; Spencer, R.; Kadler, M.; Church, M.; Balucinska-Church, M.; Wilms, J.; Hanke, M.; Zola, S.; Schulz, N.

    2009-05-01

    The neutron star X-ray binary Cygnus X-2 was observed using the e- EVN (European VLBI Network) on May 12/13th 2009 between 23:00-13:00 UT at 5 GHz. The radio telescopes participating with the e-EVN at 5 GHz were Effelsberg, Medicina, Onsala 25m, Torun, Sheshan, Yebes, Jodrell Bank MKII, Cambridge and Knockin. A maximum data rate of 1024 Mbps were achieved from four telescopes (Effelsberg, Onsala, Torun and Jodrell Bank MKII).

  16. Radio quiet, please! - protecting radio astronomy from interference

    CERN Document Server

    Van Driel, W

    2009-01-01

    The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial. The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels - national, regional and worldwide. The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%. The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of sp...

  17. Radio structures of a complete sample of quasars from the 4C catalog

    International Nuclear Information System (INIS)

    Radio observations are reported for 57 quasars. Included are all of the quasars of Schmidt's 1974 complete sample from the 4C catalog. The observations were made with the Green Bank interferometer at 2.7 and 8.1 GHz, with baselines ranging from 300 m to 35 km. Model brightness distributions are presented, consisting of one to four elliptical Gaussian components. Angular sizes range from <0.2 to 77 arcsec. Of 38 well-resolved sources 21 contain a compact central component coincident with the optical object. The quasar 4C32. 69=2349+328 appears to exhibit a jetlike structure connecting the central component to one of the outer lobes

  18. Vanishing Absorption and Blueshifted Emission in FeLoBAL Quasars

    CERN Document Server

    Rafiee, Alireza; Hall, Patrick B; Galati, Natalee; Rogerson, Jesse; Ameri, Abtin

    2016-01-01

    We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. We report on the continued weakening of absorption in the prototype of this class of variable broad absorption line quasar, FBQS J140806.2+305448. We also report a third example of this class, SDSS J123103.70+392903.6; unlike the other two examples, it has undergone an increase in observed continuum brightness (at 3000~\\AA\\ rest-frame) as well as a decrease in iron absorption strength. These changes could be caused by absorber transverse motion or by ionization variability. We note that the \\mgii\\ and UV \\feii\\ lines in several FeLoBAL quasars are blueshifted by thousands of \\kms\\ relative to the \\Hb\\ emission line peak. We suggest that such emission arises in the outflowing winds normally seen only in absorption.

  19. The time-delay of the gravitationally lensed double quasar UM 673

    CERN Document Server

    Akhunov, T A; Burkhonov, O; Gaynullina, E R; Gottlöber, S; Mirtadjieva, K; Nuritdinov, S N; Tadjibaev, I; Wambsganss, J; Wisotzki, L; Bruevich, V V; Gusev, A S; Sergeyev, A; Smirnov, G

    2008-01-01

    We present the results of a monitoring campaign of the gravitational double quasar UM 673 at Maydanak observatory from August 2001 to December 2006. We obtained light curves in the V-filter (101 nights) and the R-filter (208 nights), split up into five observing seasons. We find brightness variations and V-R colour variations of the quasar on time scales of several years. The observing conditions at the telescope limited individual observing seasons to less than 150 days, which makes the estimation of the time-delay between the two lensed images by light curve correlation difficult. To overcome this problem we introduce a novel technique to measure the time-delay from the variation of the V-R colour of the quasar, and use this to obtain a time-delay Delta t=(106.8 days\\pm 17.0) days at 68 per cent confidence (image A leading).

  20. A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates

    CERN Document Server

    Charisi, M; Haiman, Z; Price-Whelan, A M; Graham, M J; Bellm, E C; Laher, R R; Marka, S

    2016-01-01

    Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be common in galactic nuclei, as a result of frequent galaxy mergers. Hydrodynamical simulations of circumbinary discs predict strong periodic modulation of the mass accretion rate on time-scales comparable to the orbital period of the binary. As a result, SMBHBs may be recognized by the periodic modulation of their brightness. We conducted a statistical search for periodic variability in a sample of 35,383 spectroscopically confirmed quasars in the photometric database of the Palomar Transient Factory (PTF). We analysed Lomb-Scargle periodograms and assessed the significance of our findings by modeling each individual quasar's variability as a damped random walk (DRW). We identified 50 quasars with significant periodicity beyond the DRW model, typically with short periods of a few hundred days. We find 33 of these to remain significant after a re-analysis of their periodograms including additional optical data from the intermediate-PT...

  1. HOW TO IDENTIFY AND SEPARATE BRIGHT GALAXY CLUSTERS FROM THE LOW-FREQUENCY RADIO SKY

    International Nuclear Information System (INIS)

    In this work, we simulate the 50-200 MHz radio sky that is constrained in the field of view (50 radius) of the 21 Centimeter Array (21CMA), a low-frequency radio interferometric array constructed in the remote area of Xinjiang, China, by carrying out Monte Carlo simulations to model the strong contaminating foreground of the redshifted cosmological reionization signals, including emissions from our Galaxy, galaxy clusters, and extragalactic discrete sources (i.e., star-forming galaxies, radio-quiet active galactic nuclei (AGNs), and radio-loud AGNs). As an improvement over previous works, we consider in detail not only random variations of morphological and spectroscopic parameters within the ranges allowed by multi-band observations, but also the evolution of radio halos in galaxy clusters, assuming that relativistic electrons are re-accelerated in the intracluster medium (ICM) in merger events and lose energy via both synchrotron emission and inverse Compton scattering with cosmic microwave background photons. By introducing a new approach designed on the basis of independent component analysis and wavelet detection algorithm, we prove that, with a cumulative observation of one month with the 21CMA array, about 80% of galaxy clusters (37 out of 48 clusters assuming a mean magnetic field of B = 2 μG in the ICM, or 15 out of 18 clusters assuming B = 0.2 μG) with central brightness temperatures of >10 K at 65 MHz can be safely identified and separated from the overwhelmingly bright foreground. By examining the brightness temperature images and spectra extracted from these identified clusters, we find that the morphological and spectroscopic distortions are extremely small compared to the input simulated clusters, and the reduced χ2 of brightness temperature profiles and spectra are controlled to be ∼<0.5 and ∼<1.3, respectively. These results robustly indicate that in the near future a sample of dozens of bright galaxy clusters will be disentangled from the

  2. Quasar Structure and Cosmological Feedback

    CERN Document Server

    Elvis, M

    2006-01-01

    Feedback from quasars and AGNs is being invoked frequently in several cosmological settings. Currently, order of magnitude, or more, uncertainties in the structure of both the wind and the 'obscuring torus' make predictions highly uncertain. To make testable models of this 'cosmological feedback' it is essential to understand the detailed structure of AGNs sufficiently well to predict their properties for the whole quasar population, at all redshifts. Progress in both areas is rapid, and I describe the near-term prospects for reducing these uncertainties for 'slow' (non-relativistic) AGN winds and the obscuring torus.

  3. Direct determination of quasar redshifts

    CERN Document Server

    De Bruijne, J H J; Perryman, M; Peacock, A; Favata, F; Rando, N; Martin, D; Verhoeve, P; Christlieb, N; Bruijne, Jos de; Reynolds, Alastair P; Perryman, Michael; Peacock, Anthony; Favata, Fabio; Rando, Nicola; Martin, Didier; Verhoeve, Peter; Christlieb, Norbert

    2001-01-01

    We present observations of 11 quasars, selected in the range z = 2.2-4.1, obtained with ESA's Superconducting Tunnel Junction (STJ) camera on the WHT. Using a single template quasar spectrum, we show that we can determine the redshifts of these objects to about 1%. A follow-up spectroscopic observation of one QSO for which our best-fit redshift (z = 2.976) differs significantly from the tentative literature value (z ~ 2.30) confirms that the latter was incorrect.

  4. Stars, Galaxies and Quasars

    Directory of Open Access Journals (Sweden)

    Patrick Das Gupta

    2009-05-01

    Full Text Available This article provides a brief introduction to the basics of stars, galaxies and Quasi-stellar objects (QSOs. In stars, the central pressure and temperature must be high in order to halt the stellar gravitational collapse. High temperature leads to thermonuclear fusion in the stellar core, releasing thereby enormous amount of nuclear energy, making the star shine brilliantly. On the other hand, the QSOs are very bright nuclei lying in the centres of some galaxies. Many of these active galactic nuclei, which appear star-like when observed through a telescope and  whose power output are more than 1011 times that of the Sun, exhibit rapid time variability in their X-ray emissions.  Rapid variability along with the existence of a maximum speed limit, c, provide a strong argument in favour of a compact central engine model for QSOs in which a thick disc of hot gas going around a supermassive blackhole is what makes a QSO appear like a bright point source. Hence, unlike stars, QSOs are powered by gravitational potential energy.

  5. Burkina Faso - BRIGHT II

    Data.gov (United States)

    Millenium Challenge Corporation — Millennium Challenge Corporation hired Mathematica Policy Research to conduct an independent evaluation of the BRIGHT II program. The three main research questions...

  6. Extremely Red Quasars in BOSS

    CERN Document Server

    Hamann, Fred; Ross, Nicholas; Paris, Isabelle; Alexandroff, Rachael M; Villforth, Carolin; Richards, Gordon T; Herbst, Hanna; Brandt, W Niel; Cook, Ben; Denney, Kelly D; Greene, Jenny E; Schneider, Donald P; Strauss, Michael A

    2016-01-01

    Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual "wingless" line profiles, large NV/Lya, NV/CIV, SiIV/CIV and other flux ratios, and very broad and blueshifted [OIII] 5007. Here we present a new catalog of CIV and NV emission-line data for 216,188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR color, secondarily on REW(CIV), and not at all on luminosity or the Baldwin Effect. We identify a "core" sample of 97 ERQs with nearly uniform peculiar properties selected via i-W3 > 4.6 (AB) and REW(CIV) > 100 A at redshifts 2.0-3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity log L (ergs/s) ~ 47.1, sk...

  7. The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys

    CERN Document Server

    Huo, Zhi-Ying; Xiang, Mao-Sheng; Yuan, Hai-Bo; Huang, Yang; Zhang, Hui-Hua; Yan, Lin; Bai, Zhong-Rui; Chen, Jian-Jun; Chen, Xiao-Yan; Chu, Jia-Ru; Chu, Yao-Quan; Cui, Xiang-Qun; Du, Bing; Hou, Yong-Hui; Hu, Hong-Zhuan; Hu, Zhong-Wen; Jia, Lei; Jiang, Fang-Hua; Lei, Ya-Juan; Li, Ai-Hua; Li, Guang-Wei; Li, Guo-Ping; Li, Jian; Li, Xin-Nan; Li, Yan; Li, Ye-Ping; Liu, Gen-Rong; Liu, Zhi-Gang; Lu, Qi-Shuai; Luo, A-Li; Luo, Yu; Men, Li; Ni, Ji-Jun; Qi, Yong-Jun; Qi, Zhao-Xiang; Shi, Jian-Rong; Shi, Huo-Ming; Sun, Shi-Wei; Tang, Zheng-Hong; Tian, Yuan; Tu, Liang-Ping; Wang, Dan; Wang, Feng-Fei; Wang, Gang; Wang, Jia-Ning; Wang, Lei; Wang, Shu-Qing; Wang, You; Wang, Yue-Fei; Wei, Ming-Zhi; Wu, Yue; Xue, Xiang-Xiang; Yao, Zheng-Qiu; Yu, Yong; Yuan, Hui; Zhai, Chao; Zhang, En-Peng; Zhang, Hao-Tong; Zhang, Jian-Nan; Zhang, Wei; Zhang, Yan-Xia; Zhang, Yong; Zhang, Zhen-Chao; Zhao, Gang; Zhao, Ming; Zhao, Yong-Heng; Zhou, Fang; Zhou, Xin-Lin; Zhu, Yong-Tian; Zou, Si-Cheng

    2013-01-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the LAMOST during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m telescope, XSTPS optical, and WISE near infrared photometric data. We present 509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new quasars discovered in an area of ~100 sq. deg that covers the central region and the southeastern halo of M31 in the 2010 commissioning datasets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0 respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars provide an invaluable c...

  8. The double quasar 0957 + 561 AB as a probe of quasar structure

    International Nuclear Information System (INIS)

    If the individual components of the double quasar exhibit uncorrelated time-variations, it will become possible to estimate the size and number of clouds in the region of the quasar in which the emission lines are formed. (author)

  9. The SDSS-III BOSS quasar lens survey: discovery of 13 gravitationally lensed quasars

    Science.gov (United States)

    More, Anupreeta; Oguri, Masamune; Kayo, Issha; Zinn, Joel; Strauss, Michael A.; Santiago, Basilio X.; Mosquera, Ana M.; Inada, Naohisa; Kochanek, Christopher S.; Rusu, Cristian E.; Brownstein, Joel R.; da Costa, Luiz N.; Kneib, Jean-Paul; Maia, Marcio A. G.; Quimby, Robert M.; Schneider, Donald P.; Streblyanska, Alina; York, Donald G.

    2016-02-01

    We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( ≲ 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs ≈ 4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

  10. The SDSS-III BOSS quasar lens survey: discovery of thirteen gravitationally lensed quasars

    CERN Document Server

    More, Anupreeta; Kayo, Issha; Zinn, Joel; Strauss, Michael A; Santiago, Basilio X; Mosquera, Ana M; Inada, Naohisa; Kochanek, Christopher S; Rusu, Cristian E; Brownstein, Joel R; da Costa, Luiz N; Kneib, Jean-Paul; Maia, Marcio A G; Quimby, Robert M; Schneider, Donald P; Streblyanska, Alina; York, Donald G

    2015-01-01

    We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ($\\lesssim$2") confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs$\\approx$4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

  11. BLOWIN' IN THE WIND: BOTH ''NEGATIVE'' AND ''POSITIVE'' FEEDBACK IN AN OBSCURED HIGH-z QUASAR

    Energy Technology Data Exchange (ETDEWEB)

    Cresci, G.; Mannucci, F. [INAF-Osservatorio Astrofisco di Arcetri, largo E. Fermi 5, I-50127, Firenze (Italy); Mainieri, V. [European Southern Observatory, Karl-Schwarzschild-strasse 2, D-85748 Garching bei München (Germany); Brusa, M.; Perna, M.; Lanzuisi, G. [Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Marconi, A. [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, via G. Sansone 1, I-50019 Sesto F.no, Firenze (Italy); Piconcelli, E.; Feruglio, C.; Fiore, F.; Bongiorno, A. [INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy); Maiolino, R. [Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge (United Kingdom); Merloni, A [Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München (Germany); Schramm, M.; Silverman, J. D. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Civano, F., E-mail: gcresci@arcetri.astro.it [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, PO Box 208121, New Haven, CT 06520-8121 (United States)

    2015-01-20

    Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, preventing massive galaxies to overgrow and producing the red colors of ellipticals. On the other hand, some models are also requiring ''positive'' active galactic nucleus feedback, inducing star formation in the host galaxy through enhanced gas pressure in the interstellar medium. However, finding observational evidence of the effects of both types of feedback is still one of the main challenges of extragalactic astronomy, as few observations of energetic and extended radiatively driven winds are available. Here we present SINFONI near infrared integral field spectroscopy of XID2028, an obscured, radio-quiet z = 1.59 QSO detected in the XMM-COSMOS survey, in which we clearly resolve a fast (1500 km s{sup –1}) and extended (up to 13 kpc from the black hole) outflow in the [O III] lines emitting gas, whose large velocity and outflow rate are not sustainable by star formation only. The narrow component of Hα emission and the rest frame U-band flux from Hubble Space Telescope/Advanced Camera for Surveys imaging enable to map the current star formation in the host galaxy: both tracers independently show that the outflow position lies in the center of an empty cavity surrounded by star forming regions on its edge. The outflow is therefore removing the gas from the host galaxy (''negative feedback''), but also triggering star formation by outflow induced pressure at the edges (''positive feedback''). XID2028 represents the first example of a host galaxy showing both types of feedback simultaneously at work.

  12. Four Quasars above Redshift 6 Discovered by the Canada-France High-z Quasar Survey

    Science.gov (United States)

    Willott, Chris J.; Delorme, Philippe; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reylé, Céline; Hill, Gary J.; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B.; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-12-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshifts greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z = 6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars, finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise ratio optical spectra, we use the spectra to investigate the ionization state of hydrogen at z > 5. For CFHQS J1509-1749 at z = 6.12 we find significant evolution (beyond a simple extrapolation of lower redshift data) in the Gunn-Peterson optical depth at z > 5.4. The line of sight to this quasar has one of the highest known optical depths at z approx 5.8. An analysis of the sizes of the highly ionized near-zones in the spectra of two quasars at z = 6.12 and 6.43 suggest that the intergalactic medium surrounding these quasars was substantially ionized before these quasars turned on. Together, these observations point toward an extended reionization process, but we caution that cosmic variance is still a major limitation in z > 6 quasar observations.

  13. Decoding quasars: gravitationally redshifted spectral lines !

    CERN Document Server

    Kantharia, Nimisha G

    2016-01-01

    Further investigation of data on quasars, especially in the ultraviolet band, yields an amazingly coherent narrative which we present in this paper. Quasars are characterised by strong continuum emission and redshifted emission and absorption lines which includes the famous Lyman $\\alpha$ forest. We present irrefutable evidence in support of (1) the entire line spectrum arising in matter located inside the quasar system, (2) the range of redshifts shown by the lines being due to the variable contribution of the gravitational redshift in the observed line velocity, (3) existence of rotating black holes and of matter inside its ergosphere, (4) quasars located within cosmological redshifts $\\sim 3$, (5) $\\gamma$ ray bursts being explosive events in a quasar. These results are significant and a game-changer when we realise that the absorbing gas has been postulated to exist along the line-of-sight to the quasar and observations have accordingly been interpreted. In light of these definitive results which uniquely...

  14. Constraining the lifetime and opening angle of quasars using fluorescent Ly a emission: the case of Q0420-388

    CERN Document Server

    Borisova, Elena; Cantalupo, Sebastiano; Prochaska, J Xavier; Rakic, Olivera; Worseck, Gabor

    2015-01-01

    A toy model is developed to understand how the spatial distribution of fluorescent emitters in the vicinity of bright quasars could be affected by the geometry of the quasar bi-conical radiation field and by the quasar lifetime. We then compare the predictions of this model to a sample of high equivalent width Ly a emitters (EW0 > 100 A) that were identified in a deep narrow-band 36x36 arcmin2 image centered on the luminous quasar Q0420-388. These are identified to the edge of the field and show some evidence of an azimuthal asymmetry on the sky of the type expected if the quasar is radiating in a bipolar cone. If these sources are being fluorescently illuminated by the quasar, then the two most distant sources require a lifetime of at least 15 Myr for an opening angle of 60 degrees or more, increasing to more than 40 Myr if the opening angle is reduced to a minimum 30 degrees. The overall distribution of all of the sources across the field gives best fit lifetimes in the range 20 < t < 50 Myr for openi...

  15. Various Approaches for Targeting Quasar Candidates

    Science.gov (United States)

    Zhang, Y.; Zhao, Y.

    2015-09-01

    With the establishment and development of space-based and ground-based observational facilities, the improvement of scientific output of high-cost facilities is still a hot issue for astronomers. The discovery of new and rare quasars attracts much attention. Different methods to select quasar candidates are in bloom. Among them, some are based on color cuts, some are from multiwavelength data, some rely on variability of quasars, some are based on data mining, and some depend on ensemble methods.

  16. The Stacked Lyman-Alpha Emission Profile from the Circum-Galactic Medium of z~2 Quasars

    CERN Document Server

    Battaia, Fabrizio Arrigoni; Cantalupo, Sebastiano; Prochaska, J Xavier

    2016-01-01

    In the context of the FLASHLIGHT survey, we obtained deep narrow band images of 15 $z\\sim2$ quasars with GMOS on Gemini-South in an effort to measure Ly$\\alpha$ emission from circum- and inter-galactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Ly$\\alpha$ nebulae (SB~10$^{-17}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ at distances >50 kpc) around any of our sources, although we routinely ($\\simeq47$%) detect smaller scale <50 kpc Ly$\\alpha$ emission at this SB level emerging from either the extended narrow emission line regions powered by the quasars or by star-formation in their host galaxies. We stack our 15 deep images to study the average extended Ly$\\alpha$ surface brightness profile around $z\\sim2$ quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SB$_{\\rm Ly\\alpha}\\sim10^{-19}$ erg s$^{-1}$ cm$^{-2}...

  17. Sunspot Bright Points

    CERN Document Server

    Choudhary, Debi Prasad

    2010-01-01

    We used the flux calibrated images through the Broad Band Filter Imager and Stokes Polarimeter data obtained with the Solar Optical Telescope onboard the Hinode spacecraft to study the properties of bright points in and around the sunspots. The well isolated bright points were selected and classified as umbral dot, peripheral umbral dot, penumbral grains and G-band bright point depending on their location. Most of the bright points are smaller than about 150 km. The larger points are mostly associated with the penumbral features. The bright points are not uniformly distributed over the umbra but preferentially located around the penumbral boundary and in the fast decaying parts of umbra. The color temperature of the bright points, derived using the continuum irradiance, are in the range of 4600 K to 6600 K with cooler ones located in the umbra. The temperature increases as a function of distance from the center to outside. The G-band, CN-band and CaII H flux of the bright points as a function of their blue ba...

  18. Comparing Simple Quasar Demographics Models

    CERN Document Server

    Veale, Melanie; Conroy, Charlie

    2014-01-01

    This paper explores several simple model variations for the connections among quasars, galaxies, and dark matter halos for redshifts 1 < z < 6. A key component of these models is that we enforce a self-consistent black hole (BH) history by tracking both BH mass and BH growth rate at all redshifts. We connect objects across redshift with a simple constant-number-density procedure, and choose a fiducial model with a relationship between BH and galaxy growth rates that is linear and evolves in a simple way with redshift. Within this fiducial model, we find the quasar luminosity function (QLF) by calculating an "intrinsic" luminosity based on either the BH mass or BH growth rate, and then choosing a model of quasar variability with either a lognormal or truncated power-law distribution of instantaneous luminosities. This gives four model variations, which we fit to the observed QLF at each redshift. With the best-fit models in hand, we undertake a detailed comparison of the four fiducial models, and explore...

  19. Functional Regression for Quasar Spectra

    CERN Document Server

    Ciollaro, Mattia; Freeman, Peter; Genovese, Christopher; Lei, Jing; O'Connell, Ross; Wasserman, Larry

    2014-01-01

    The Lyman-alpha forest is a portion of the observed light spectrum of distant galactic nuclei which allows us to probe remote regions of the Universe that are otherwise inaccessible. The observed Lyman-alpha forest of a quasar light spectrum can be modeled as a noisy realization of a smooth curve that is affected by a `damping effect' which occurs whenever the light emitted by the quasar travels through regions of the Universe with higher matter concentration. To decode the information conveyed by the Lyman-alpha forest about the matter distribution, we must be able to separate the smooth `continuum' from the noise and the contribution of the damping effect in the quasar light spectra. To predict the continuum in the Lyman-alpha forest, we use a nonparametric functional regression model in which both the response and the predictor variable (the smooth part of the damping-free portion of the spectrum) are function-valued random variables. We demonstrate that the proposed method accurately predicts the unobserv...

  20. Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey

    CERN Document Server

    Willott, Chris J; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reyle, Celine; Hill, Gary J; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-01-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshift greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise optical spectra, we use the spectra to investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at z=6.12, we find significant evol...

  1. Observations Supporting the Existence of an Intrinsic Magnetic Moment Inside the Central Compact Object Within the Quasar Q0957+561

    CERN Document Server

    Schild, R E; Robertson, S L; Schild, Rudolph E.; Leiter, Darryl J.; Robertson, Stanley L.

    2005-01-01

    Recent auto-correlation and fluctuation analysis of time series data in the brightness curves and micro-lensing size scales seen in Q0957+561 A,B has produced important information about the existence and characteristic physical dimensions of a new non-standard internal structure contained within this quasar. We find that the new internal quasar structure, which we shall call the Schild-Vakulik Structure, can be consistently explained in terms of a new calss of gravitationally collapsing solutions to the Einstein field equations which describe highly redshifted, Eddington limited, Magnetospheric Eternally Collapsing Objects (MECO) that contain intrinsic magnetic moments. Since observation of the Schild-Vakulik structure within Q0957+561 implies that this quasar contains an observable intrinsic magnetic moment, this represents strong evidence that this quasar does not have an event horizon

  2. Quasars - powerhouses at the edge of time

    Science.gov (United States)

    Gavin, M.

    2000-06-01

    1999 was the 70th anniversary of Edwin Hubble's seminal publication1 showing a cosmological redshift in galaxies. More recent discoveries of quasars have extended the universe's boundaries back in time nearer to the Big Bang. Some amateur spectrograms of quasars are presented showing a cosmological redshift.

  3. Quasar Evolution Driven by Galaxy Encounters in Hierarchical Structures

    CERN Document Server

    Menci, N; Fontana, A; Giallongo, E; Poli, F; Vittorini, V

    2003-01-01

    We link the evolution of the galaxies in the hierarchical clustering scenario with the changing accretion rates of cold gas onto the central massive black holes that power the quasars. We base on galaxy interactions as main triggers of accretion; the related scaling laws are taken up from Cavaliere & Vittorini (2000), and grafted to a semi-analytic code for galaxy formation. As a result, at high $z$ the protogalaxies grow rapidly by hierarchical merging; meanwhile, much fresh gas is imported and also destabilized, so the holes are fueled at their full Eddington rates. At lower $z$ the galactic dynamical events are mostly encounters in hierarchically growing groups; now the refueling peters out, as the residual gas is exhausted while the destabilizing encounters dwindle. So, with no parameter tuning other than needed for stellar observables, our model uniquely produces at $z>3$ a rise, and at $z\\lesssim 2.5 $ a decline of the bright quasar population as steep as observed. In addition, our results closely f...

  4. New lensed quasars from the MUSCLES survey

    CERN Document Server

    Jackson, Neal; Ofek, Eran O; Shin, Min-Su

    2011-01-01

    Gravitational lens systems containing lensed quasars are important as cosmological probes, as diagnostics of structural properties of the lensing galaxies and as tools to study the quasars themselves. The largest lensed quasar sample is the SDSS Quasar Lens Search, drawn from the Sloan Digital Sky Survey (SDSS). We are attempting to extend this survey using observations of lens candidates selected from a combination of the quasar sample from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). This adds somewhat higher image quality together with a wider range of wavelength for the selection process. In previous pilot surveys we observed 5 objects, finding 2 lenses; here we present further observations of 20 objects in which we find 4 lenses, of which 2 are independently discovered in SQLS (in preparation). Following earlier work on the combination of these two surveys, we have refined our method and find that use of a colour-separation diagnostic, where we select for separations between components which...

  5. The Neutrino Ball Model of a Quasar

    CERN Document Server

    Manka, R; Karczewska, D

    1993-01-01

    It is suggested that the nonorthodox model of a quasar as a neutrino ball described in terms of the standard model extended by adding right-handed neutrinos and the Majorana scalar field can be presented in order to explain a quasar as a body of weak interacting neutrinos. Neutrino interaction with the scalar Majorana field violates the lepton number and produces the mass splitting of the neutrino due to the sea-saw mechanism. In this model a quasar is an object which appears in the result of the first order cosmological phase transition. In this interpretation a quasar may be regarded as a ball filled with Dirac neutrinos and can be treated as a remnant of phase transition with unbroken global lepton symmetry. In this paper we study the macroscopic parameters of such a configuration. In the result the mass-radius curve M(R) for the quasar is obtained.

  6. The Mass Budget of Merging Quasars

    CERN Document Server

    Menou, K

    2004-01-01

    Two spectacular results emerging from recent studies of nearby dead quasars and distant active quasars are (i) the existence of tight relations between the masses of black holes (BHs) and the properties of their host galaxies (spheroid luminosity or velocity dispersion, galaxy mass), and (ii) a consistency between the local mass density in BHs and that expected by summing up the light received from distant active quasars. These results are partly shaped by successive galactic mergers and BH coalescences, since mergers redistribute the population of BHs in galaxies and BH binary coalescences reduce the mass density in BHs through losses to gravitational waves. Here, we isolate and quantify these effects by following the cosmological merger history of a population of massive BHs representing the quasar population between z = 3 and z =0. Our results suggest that the relation between BH mass and host galaxy properties, and inferences on the global efficiency of BH accretion during active quasar phases, could be i...

  7. Adaptive optics imaging of low and intermediate redshift quasars

    CERN Document Server

    Márquez, I; Theodore, B; Bremer, M; Monnet, G; Beuzit, J L

    2001-01-01

    We present the results of adaptive-optics imaging in the H and K bands of 12 low and intermediate redshift (z15.0) themselves as reference for the correction, have typical spatial resolution of FWHM~0.3 arcsec before deconvolution. The deconvolved H-band image of PG1700+514 has a spatial resolution of 0.16 arcsec and reveals a wealth of details on the companion and the host-galaxy. Four out of the twelve quasars have close companions and obvious signs of interactions. The two-dimensional images of three of the host-galaxies unambiguously reveal bars and spiral arms. The morphology of the other objects are difficult to determine from one dimensional surface brightness profile and deeper images are needed. Analysis of mocked data shows that elliptical galaxies are always recognized as such, whereas disk hosts can be missed for small disk scale lengths and large QSO contributions.

  8. The extended Baryon Oscillation Spectroscopic Survey: Variability selection and quasar luminosity function

    Science.gov (United States)

    Palanque-Delabrouille, N.; Magneville, Ch.; Yèche, Ch.; Pâris, I.; Petitjean, P.; Burtin, E.; Dawson, K.; McGreer, I.; Myers, A. D.; Rossi, G.; Schlegel, D.; Schneider, D.; Streblyanska, A.; Tinker, J.

    2016-03-01

    The extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey (SDSS-IV/eBOSS) has an extensive quasar program that combines several selection methods. Among these, the photometric variability technique provides highly uniform samples, which are unaffected by the redshift bias of traditional optical-color selections, when z = 2.7-3.5 quasars cross the stellar locus or when host galaxy light affects quasar colors at z 2.2. Both models are constrained to be continuous at z = 2.2. They present a flattening of the bright-end slope at high redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3% (resp., 1.1%) to g< 22.5 (resp., g< 23). The models are also in good agreement over the entire redshift range with models from previous studies.

  9. Spectral Variability of Quasars in the Sloan Digital Sky Survey. I: Wavelength Dependence

    CERN Document Server

    Wilhite, B C; Kron, R G; Schneider, D P; Pereyra, N; Brunner, R J; Richards, G T; Brinkmann, J; Wilhite, Brian C.; Berk, Daniel E. Vanden; Kron, Richard G.; Schneider, Donald P.; Pereyra, Nicholas; Brunner, Robert J.; Richards, Gordon T.; Brinkmann, Jonathan V.

    2005-01-01

    Sloan Digital Sky Survey (SDSS) repeat spectroscopic observations have resulted in multiple-epoch spectroscopy for roughly 2500 quasars observed more than 50 days apart. From this sample, we identify 315 quasars that have varied significantly between observations. We create an ensemble difference spectrum (bright phase minus faint phase) covering rest-frame wavelengths from 1000 to 6000 Angstroms. This average difference spectrum is bluer than the average single-epoch quasar spectrum; a power-law fit to the difference spectrum yields a spectral index alpha_lambda = -2.00, compared to an index of alpha_lambda = -1.35 for the single-epoch spectrum. The strongest emission lines vary only 30% as much as the continuum. Due to the lack of variability of the lines, measured photometric color is not always bluer in brighter phases, but depends on redshift and the filters used. Lastly, the difference spectrum is bluer than the ensemble quasar spectrum only for lambda_rest < 2500 Angstroms, indicating that the varia...

  10. The Host Galaxies of High-Luminosity Obscured Quasars at 2.5

    Science.gov (United States)

    Ross, Nicholas; Strauss, M. A.; Greene, J. E.; Zakamska, N. L.; Brandt, W. N.; Alexandroff, R.; Liu, G.; Smith, P. S.; The SDSS-III BOSS Quasar Working Group

    2014-01-01

    Active Galactic Nuclei play a key role in the evolution of galaxies. However, very little is known about the host galaxies of the most luminous quasars at redshift 2.5, the epoch when massive black hole growth peaked. The brightness of the quasar itself, which can easily outshine a galaxy by a large factor, makes it very difficult to study emission from extended gas or stars in the host galaxy. However, we have imaged the extended emission from the host galaxies of a unique sample of six optically extinguished (Type II) luminous quasars with 2.5, with the Hubble Space Telescope (Cycle 20, GO 13014) using ACS/F814W to access the rest-frame near-ultraviolet, and WFC3/F160W for the rest-frame optical longward of 4000A. These objects are selected from the spectroscopic database of the SDSS/Baryon Oscillation Spectroscopic Survey to have strong, narrow emission lines and weak continua. With these images, we have quantified the luminosity, morphology, and dynamical state of the host galaxies, and searched for extended scattered light from the obscured central engine. These observations are the first comprehensive study of both host galaxy light and scattered light in high-luminosity quasars at the epoch of maximum black hole growth, and give insights into the relationship between host galaxies and black holes during this important, and yet largely unexplored period.

  11. The Impact of Dust in Host Galaxies on Quasar Luminosity Functions

    CERN Document Server

    Shirakata, H; Enoki, M; Nagashima, M; Kobayashi, M A R; Ishiyama, T; Makiya, R

    2014-01-01

    We have investigated effects of dust attenuation on quasar luminosity functions using a semi-analytic galaxy formation model combined with a large cosmological N-body simulation. We estimate the dust attenuation of quasars self-consistently with that of galaxies by considering the dust in their host bulges.We find that the luminosity of the bright quasars is strongly dimmed by the dust attenuation, about 2 mag in the B-band, and that the faint end slope of the luminosity function is steepened. We also study for the first time the case in which gas fueling to a central black hole starts some time after the beginning of the starburst induced by a major merger. In this case, nuclei are less attenuated by the dust since the cold gas in the bulges is consumed by the starbursts and expelled by the stellar feedback. In order to make the dust attenuation of the quasars negligible, the accretion has to be delayed at least five times the dynamical timescale of their host bulges.

  12. Evidence for the alignment of quasar radio polarizations with large quasar group axes

    Science.gov (United States)

    Pelgrims, V.; Hutsemékers, D.

    2016-05-01

    Recently, evidence has been presented for the polarization vectors from quasars to preferentially align with the axes of the large quasar groups (LQG) to which they belong. This report was based on observations made at optical wavelengths for two LQGs at redshift ~1.3. The correlation suggests that the spin axes of quasars preferentially align with their surrounding large-scale structure that is assumed to be traced by the LQGs. Here, we consider a large sample of LQGs built from the Sloan Digital Sky Survey DR7 quasar catalogue in the redshift range 1.0-1.8. For quasars embedded in this sample, we collected radio polarization measurements with the goal to study possible correlations between quasar polarization vectors and the major axis of their host LQGs. Assuming the radio polarization vector is perpendicular to the quasar spin axis, we found that the quasar spin axis is preferentially parallel to the LQG major axis inside LQGs that have at least 20 members. This result independently supports the observations at optical wavelengths. We additionally found that when the richness of an LQG decreases, the quasar spin axis becomes preferentially perpendicular to the LQG major axis and that no correlation is detected for quasar groups with fewer than 10 members.

  13. Tracing dark energy with quasars

    CERN Document Server

    Średzińska, J; Bilicki, M; Hryniewicz, K; Krupa, M; Kurcz, A; Marziani, P; Pollo, A; Pych, W; Udalski, A

    2016-01-01

    The nature of dark energy, driving the accelerated expansion of the Universe, is one of the most important issues in modern astrophysics. In order to understand this phenomenon, we need precise astrophysical probes of the universal expansion spanning wide redshift ranges. Quasars have recently emerged as such a probe, thanks to their high intrinsic luminosities and, most importantly, our ability to measure their luminosity distances independently of redshifts. Here we report our ongoing work on observational reverberation mapping using the time delay of the Mg II line, performed with the South African Large Telescope (SALT).

  14. HST images of FeLoBAL quasars: Testing quasar-galaxy evolution models

    Science.gov (United States)

    Herbst, Hanna; Hamann, Fred; Villforth, Carolin; Caselli, Paola; Koekemoer, Anton M.; Veilleux, Sylvain

    2016-01-01

    We present preliminary results from an HST imaging study of FeLoBAL quasars, which have extremely low-ionization Broad Absorption Line (BAL) outflows and might be a young quasar population based on their red colors, large far-IR luminosities (suggesting high star formation rates), and powerful outflows. Some models of quasar - host galaxy evolution propose a triggering event, such as a merger, to fuel both a burst of star formation and the quasar/AGN activity. These models suggest young quasars are initially obscured inside the dusty starburst until a "blowout" phase, driven by the starburst or quasar outflows like FeLoBALs, ends the star formation and reveals the visibly luminous quasar. Despite the popularity of this evolution scheme, there is little observational evidence to support the role of mergers in triggering AGN or the youth of dust-reddened quasars (such as FeLoBALs) compared to normal blue quasars.Our Cycle 22 HST program is designed to test the youth of FeLoBAL quasars and the connection of FeLoBALs to mergers. We obtain WFC3/IR F160W images of 10 FeLoBAL quasars at redshift z~0.9 (covering ~8500A in the quasar rest frame). We will compare the host galaxy morphologies and merger signatures of FeLoBALs with normal blue quasars (which are older according to the evolution model) and non-AGN galaxies matched in redshift and stellar mass. If FeLoBAL quasars are indeed in a young evolutionary state, close in time to the initial merging event, they should have stronger merger features compared to blue quasars and non-AGN galaxies. Preliminary results suggest that this is not the case - FeLoBAL quasars appear to reside in faint, compact hosts with weak or absent merger signatures. We discuss the implications of these results for galaxy evolution models and other studies of dust-reddened quasar populations.

  15. Quasar Classification Using Color and Variability

    Science.gov (United States)

    Peters, Christina M.; Richards, Gordon

    2015-08-01

    We use the Non-parametric Bayesian Classification Kernel Density Estimation (NBC KDE) quasar selection algorithm (Richards et al. 2004) to identify 36,569 type 1 quasar candidates in the Sloan Digital Sky Survey (SDSS) Stripe 82 field using the combination of optical photometry and variability. 5-band coadded optical photometry is taken from the SDSS-I/II to a depth of r ~ 22.4; from these data variability parameters are calculated by fitting the structure function of each object in each band with a power law using 10 to >100 observations for timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type 1 quasars from SDSS-I/II and the Baryon Oscillation Spectroscopic Survey (BOSS). Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency respectively, with particular improvement in the selection of quasars at 2.7 < z < 3.5 where quasars and stars have similar optical colors. The 23,043 quasar candidates that are not spectroscopically confirmed reach a depth of coadd i ~ 22: 0 and 21,380 (92.8%) are dimmer than coadded i -band magnitude of 20.2, the cut off for spectroscopic follow-up for SDSSDR7.

  16. Halo Occupation Distribution of Infrared Selected Quasars

    CERN Document Server

    Mitra, Kaustav

    2016-01-01

    We perform a Halo Occupation Distribution (HOD) modeling of the projected two-point correlation function (2PCF) of quasars that are observed in the Wide-field Infrared Survey Explorer (WISE) telescope with counter-parts in the Sloan Digital Sky Survey (SDSS) Data Release (DR)-8 quasar catalog at a median redshift of $z\\sim 1.04 (\\pm 0.58)$. Using a four parameter HOD model we derive the host mass scales of WISE selected quasars. Our results show that the median halo masses of central and satellite quasars lie in the range $M_{\\mathrm{cen}} = (5 \\pm 1.0) \\times 10^{12} M_{\\odot}$ and $M_{\\mathrm{sat}} = 8 (^{+7.8} _{-4.8}) \\times 10^{13} M_{\\odot}$, respectively. The derived satellite fraction is $f_{\\mathrm{sat}}= 5.5 (^{+35} _{-5.0})\\times 10^{-3}$. Previously Richardson et al.\\ used the SDSS DR7 quasar clustering data to obtain the halo mass distributions of $z\\sim 1.4$ quasars. Our results on the HOD of central quasars are in excellent agreement with Richardson et al.\\ but the host mass scale of satellite ...

  17. Quasar Proximity Zones and Patchy Reionization

    CERN Document Server

    Lidz, A; Zaldarriaga, M; Hernquist, L; Dutta, S; Lidz, Adam; Quinn, Matthew Mc; Zaldarriaga, Matias; Hernquist, Lars; Dutta, Suvendra

    2007-01-01

    Lyman-alpha forest absorption spectra towards quasars at z ~ 6 show regions of enhanced transmission close to their source. Several authors have argued that the apparently small sizes of these regions indicate that quasar ionization fronts at z >~ 6 expand into a largely or partly neutral intergalactic medium (IGM). Assuming that the typical region in the IGM is reionized by z <= 6, as is suggested by Ly-a forest observations, we argue that at {\\em least} 50% of the volume of the IGM was reionized before the highest redshift quasars turned on. Further, even if the IGM is as much as 50% neutral at quasar turn-on, the quasars are likely born into large galaxy-generated HII regions. The HII regions during reionization are themselves clustered, and using radiative transfer simulations, we find that long skewers through the IGM towards quasar progenitor halos pass entirely through ionized bubbles, even when the IGM is half neutral. These effects have been neglected in most previous analyses of quasar proximity ...

  18. Testing Models of Quasar Hosts With Strong Gravitational Lensing by Quasar Hosts

    CERN Document Server

    Cen, Renyue

    2016-01-01

    We perform a statistical analysis of strong gravitational lensing by quasar hosts of background galaxies, in the two competing models of dark matter halos of quasars, HOD and CS models. Utilizing the BolshoiP Simulation we demonstrate that strong gravitational lensing provides a potentially very powerful test of models of quasar hosting halos. For quasars at $z=0.5$, the lensing probability by quasars of background galaxies in the HOD model is higher than that of the CS model by two orders of magnitude or more for lensing image separations in the range of $\\theta\\sim 1.2-12~$arcsec. To observationally test this, we show that, as an example, at the depth of the CANDELS wide field survey and with a quasar sample of $1000$ at $z=0.5$, the two models can be differentiated at $3-4\\sigma$ confidence level.

  19. The odd couple: quasars and black holes

    OpenAIRE

    Tremaine, Scott

    2014-01-01

    Quasars emit more energy than any other objects in the universe, yet are not much bigger than the solar system. We are almost certain that quasars are powered by giant black holes of up to $10^{10}$ times the mass of the Sun, and that black holes of between $10^6$ and $10^{10}$ solar masses---dead quasars---are present at the centers of most galaxies. Our own galaxy contains a black hole of $4.3\\times10^6$ solar masses. The mass of the central black hole appears to be closely related to other...

  20. The Stacked LYα Emission Profile from the Circum-Galactic Medium of z ˜ 2 Quasars

    Science.gov (United States)

    Arrigoni Battaia, Fabrizio; Hennawi, Joseph F.; Cantalupo, Sebastiano; Prochaska, J. Xavier

    2016-09-01

    In the context of the FLASHLIGHT survey, we obtained deep narrowband images of 15 z ˜ 2 quasars with the Gemini Multi-object Spectrograph on Gemini South in an effort to measure Lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Lyα nebulae (SB ˜ 10-17 erg s-1 cm-2 arcsec-2 at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  1. Features of thin spatial structure of the quasar 3C216 at decameter lengths of waves

    Science.gov (United States)

    Megn, A. V.; Rashkovskiy, S. L.; Shepelev, V. A.; Inytin, G. A.; Vashchishin, R. V.; Brazhenko, A. I.; Koshoviy, V. V.; Lozinskiy, A. B.

    2010-01-01

    The results of interferometric researches of the quasar 3C216 have been presented. The model of brightness distribution of the quasar at frequencies of 20 and 25 MHz and spectra of its details at frequencies below 1 GHz have been refined. It was found out, that at decameter lengths the radio image of 3C216 has three components. It consists of a compact component having the size limited by scattering, an extended component with the size of 4.5'' and a halo with the size about 23''. The northeast hot spot (instead of the core, as it was supposed earlier) is the dominating compact component at decameter waves. The self-absorption effect in the northeast hot spot has been detected.

  2. Analyses of quasar 3C 273 using XMM-Newton and RXTE

    OpenAIRE

    Stuhlinger, Martin

    2004-01-01

    Due to their tremendous luminosity over up to thirteen orders of magnitudes in frequency, active galactic nuclei (AGN) belong to the most distant discrete objects that can be observed in the universe. Except the differentiation into radio quiet AGNs and radio loud AGNs, dependent on the presence or absence of a jet, the unification model explains the different phenomenonal appearances of AGNs by a different viewing angle on the same physical kind of objects. As the brightest and nearest ...

  3. The brightness of colour.

    Directory of Open Access Journals (Sweden)

    David Corney

    Full Text Available BACKGROUND: The perception of brightness depends on spatial context: the same stimulus can appear light or dark depending on what surrounds it. A less well-known but equally important contextual phenomenon is that the colour of a stimulus can also alter its brightness. Specifically, stimuli that are more saturated (i.e. purer in colour appear brighter than stimuli that are less saturated at the same luminance. Similarly, stimuli that are red or blue appear brighter than equiluminant yellow and green stimuli. This non-linear relationship between stimulus intensity and brightness, called the Helmholtz-Kohlrausch (HK effect, was first described in the nineteenth century but has never been explained. Here, we take advantage of the relative simplicity of this 'illusion' to explain it and contextual effects more generally, by using a simple Bayesian ideal observer model of the human visual ecology. We also use fMRI brain scans to identify the neural correlates of brightness without changing the spatial context of the stimulus, which has complicated the interpretation of related fMRI studies. RESULTS: Rather than modelling human vision directly, we use a Bayesian ideal observer to model human visual ecology. We show that the HK effect is a result of encoding the non-linear statistical relationship between retinal images and natural scenes that would have been experienced by the human visual system in the past. We further show that the complexity of this relationship is due to the response functions of the cone photoreceptors, which themselves are thought to represent an efficient solution to encoding the statistics of images. Finally, we show that the locus of the response to the relationship between images and scenes lies in the primary visual cortex (V1, if not earlier in the visual system, since the brightness of colours (as opposed to their luminance accords with activity in V1 as measured with fMRI. CONCLUSIONS: The data suggest that perceptions

  4. Quasars as probes of cosmological reionization

    CERN Document Server

    Mortlock, Daniel J

    2015-01-01

    Quasars are the most luminous non-transient sources in the epoch of cosmological reionization (i.e., which ended a billion years after the Big Bang, corresponding to a redshift of z ~ 5), and are powerful probes of the inter-galactic medium at that time. This review covers current efforts to identify high-redshift quasars and how they have been used to constrain the reionization history. This includes a full description of the various processes by which neutral hydrogen atoms can absorb/scatter ultraviolet photons, and which lead to the Gunn-Peterson effect, dark gap and dark pixel analyses, quasar near zones and damping wing absorption. Finally, the future prospects for using quasars as probes of reionization are described.

  5. Quasars as tracers of cosmic flows

    CERN Document Server

    Modzelewska, J; Bilicki, M; Hryniewicz, K; Krupa, M; Petrogalli, F; Pych, W; Kurcz, A; Udalski, A

    2014-01-01

    Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to $z = 7$, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 ($z = 0.900$) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising.

  6. CA BrightStor

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CA推出的BrightStor系列存储管理解决方案已经成为企业电子商务体系架构管理战略中举足轻重的组成部分。BrightStor是一整套企业级的智能化存储管理解决方案,定位在存储硬件设备和上层应用之间,通过各种集成化的产品和工具为驻留在企业任何位置的数据提供全方位的、有效的存储管理和保护。

  7. The Physical Nature of Polar Broad Absorption Line Quasars

    Science.gov (United States)

    Ghost, Kajal; Punsly, Brian

    2007-01-01

    It has been shown based on radio variability arguments that some BALQSOs (broad absorption line quasars) are viewed along the polar axis (o rthogonal to accretion disk) in the recent article of Zhou et a. Thes e arguments are based on the brightness temperature, T(sub b) exceedi ng 10(exp 12) K which leads to the well-known inverse Compton catastr ophe unless the radio jet is relativistic and is viewed along its axi s. In this letter, we expand the Zhou et al sample of polar BALQSOs u sing their techniques applied to SDSS DR5. In the process, we clarify a mistake in their calculation of brightness temperature. The expanded sample of high T(sub b) BALQSOS, has an inordinately large fraction of LoBALQSOs (low ionization BALQSOs). We consider this an important clue to understanding the nature of the polar BALQSOs. This is expec ted in the polar BALQSO analytical/numerical models of Punsly that pr edicted that LoBALQSOs occur when the line of sight is very close to the polar axis, where the outflow density is the highest.

  8. Bright Economic Prospects

    Institute of Scientific and Technical Information of China (English)

    Zhang Minqiu

    2004-01-01

    @@ India is expected to register an 8.2% growth rate for the 2003-04 fiscal year. The overall economic situation this year has been satisfactory despite the scaled down 6-6.5% growth rate for the new fiscal year due to oil price hikes, reduced monsoon volume and some 7% inflation. Judging from the following factors, bright prospects are in store for the country down the road.

  9. Balmer line shifts in quasars

    CERN Document Server

    Sulentic, J W; Del Olmo, A; Zamfir, S

    2015-01-01

    We offer a broad review of Balmer line phenomenology in type 1 active galactic nuclei, briefly sum- marising luminosity and radio loudness effects, and discussing interpretation in terms of nebular physics along the 4D eigenvector 1 sequence of quasars. We stress that relatively rare, peculiar Balmer line profiles (i.e., with large shifts with respect to the rest frame or double and multiple peaked) that start attracted attentions since the 1970s are still passable of multiple dynamical interpretation. More mainstream objects are still not fully understood as well, since competing dynamical models and geometries are possible. Further progress may come from inter-line comparison across the 4D Eigenvector 1 sequence.

  10. Quasar clustering in a galaxy and quasar formation model based on ultra high-resolution N-body simulations

    Science.gov (United States)

    Oogi, Taira; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Makiya, Ryu; Nagashima, Masahiro

    2016-02-01

    We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations. In this study, we assume that a major merger of galaxies triggers cold gas accretion on to a supermassive black hole and quasar activity. Our model can reproduce the downsizing trend of the evolution of quasars. We find that the median mass of quasar host dark matter haloes increases with cosmic time by an order of magnitude from z = 4 (a few 1011 M⊙) to z = 1 (a few 1012 M⊙), and depends only weakly on the quasar luminosity. Deriving the quasar bias through the quasar-galaxy cross-correlation function in the model, we find that the quasar bias does not depend on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. We also show that the quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

  11. A Simple Model for Quasar Demographics

    CERN Document Server

    Conroy, Charlie

    2012-01-01

    We present a simple model for the relationship between quasars, galaxies, and dark matter halos from 0quasars is adopted, wherein BHs shine at a fixed fraction of the Eddington luminosity during accretion episodes, and Eddington ratios are drawn from a lognormal distribution that is redshift-independent. This model has two free, physically meaningful parameters at each redshift, the normalization of the M_BH-M_gal relation and the quasar duty cycle; these parameters are fit to the observed quasar luminosity function (LF) over the interval 0.5quasars from 0.5quasar duty cycle at each redshift is c...

  12. QUASARS PROBING QUASARS. VI. EXCESS H I ABSORPTION WITHIN ONE PROPER Mpc OF z ∼ 2 QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Prochaska, J. Xavier; Cantalupo, Sebastiano; Lau, Marie Wingyee [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Hennawi, Joseph F.; Lee, Khee-Gan; Myers, Adam; Rubin, Kate H. R. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69115 Heidelberg (Germany); Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Djorgovski, S. G. [California Institute of Technology, Pasadena, CA 91125 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Finnerty Road, Victoria, British Columbia V8P 1A1 (Canada); Martin, Crystal L. [Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106 (United States); Simcoe, Robert A. [MIT-Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-10-20

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ∼ 2 quasars at proper separations of 30 kpc < R < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc){sup –0.46}. We also observe a high (≅ 60%) covering factor of strong, optically thick H I absorbers (H I column N{sub H{sub I}}>10{sup 17.3} cm{sup -2}) at separations R < 200 kpc, which decreases to ∼20% at R ≅ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ{sub QA}(r) = (r/r{sub 0}){sup γ} with a large correlation length r{sub 0} = 12.5{sup +2.7}{sub -1.4} h{sup -1} Mpc (comoving) and γ=1.68{sup +0.14}{sub -0.30}. The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M{sub halo} ≈ 10{sup 12.5} M{sub ☉} at z ∼ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ∼ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  13. The Discovery of Gas-Rich, Dusty Starbursts in Luminous Reddened Quasars at $z\\sim2.5$ with ALMA

    CERN Document Server

    Banerji, Manda; Jones, G; Wagg, J; McMahon, R G; Hewett, P C; Alaghband-Zadeh, S; Feruglio, C

    2016-01-01

    We present ALMA observations of cold dust and molecular gas in four high-luminosity, heavily reddened (A$_{\\rm{V}} \\sim 2.5-6$ mag) Type 1 quasars at $z\\sim2.5$ with virial M$_{\\rm{BH}} \\sim 10^{10}$M$_\\odot$, to test whether dusty, massive quasars represent the evolutionary link between submillimetre bright galaxies (SMGs) and unobscured quasars. All four quasars are detected in both the dust continuum and in the $^{12}$CO(3-2) line. The mean dust mass is 6$\\times$10$^{8}$M$_\\odot$ assuming a typical high redshift quasar spectral energy distribution (T=41K, $\\beta$=1.95 or T=47K, $\\beta$=1.6). The implied star formation rates are very high - $\\gtrsim$1000 M$_\\odot$ yr$^{-1}$ in all cases. Gas masses estimated from the CO line luminosities cover $\\sim$1-5$\\times10^{10}$($\\alpha_{\\rm{CO}} / 0.8$)M$_\\odot$ and the gas depletion timescales are very short - $\\sim5-20$Myr. A range of gas-to-dust ratios is observed in the sample. We resolve the molecular gas in one quasar - ULASJ2315$+$0143 ($z=2.561$) - which show...

  14. The Optical Variability of SDSS Quasars from Multi-epoch Spectroscopy. III. A Sudden UV Cutoff in Quasar SDSS J2317+0005

    CERN Document Server

    Guo, Hengxiao; Gu, Minfeng; Li, Linlin; Prochaska, J Xavier; Ma, Jingzhe; You, Bei; Zafar, Tayyaba; Liao, Mai

    2016-01-01

    We have collected near-infrared to X-ray data of 20 multi-epoch heavily reddened SDSS quasars to investigate the physical mechanism of reddening. Of these, J2317+0005 is found to be a UV cutoff quasar. Its continuum, which usually appears normal, decreases by a factor 3.5 at 3000{\\AA}, compared to its more typical bright state during an interval of 23 days. During this sudden continuum cut-off, the broad emission line fluxes do not change, perhaps due to the large size of the Broad Line Region (BLR), r > 23 / (1+z) days. The UV continuum may have suffered a dramatic drop out. However, there are some difficulties with this explanation. Another possibility is that the intrinsic continuum did not change, but was temporarily blocked out, at least towards our line of sight. As indicated by X-ray observations, the continuum rapidly recovers after 42 days. A comparison of the bright state and dim states would imply an eclipse by a dusty cloud with a reddening curve having a remarkably sharp rise shortward of 3500{\\A...

  15. Low surface brightness galaxies

    Science.gov (United States)

    Vanderhulst, J. M.; Deblok, W. J. G.; Mcgaugh, S. S.; Bothun, G. D.

    1993-01-01

    A program to investigate the properties of low surface brightness (LSB) galaxies involving surface photometry in U, B, V, R, I, and H-alpha, HI imaging with the Westerbork Synthesis Radio Telescope (WSRT) and the very large array (VLA) and spectrophotometry of H2 regions in LSB galaxies is underway. The goal is to verify the idea that LSB galaxies have low star formation rates because the local gas density falls below the critical density for star formation, and to study the stellar population and abundances in LSB galaxies. Such information should help understanding the evolutionary history of LSB galaxies. Some preliminary results are reported.

  16. Quasar clustering in a galaxy and quasar formation model based on ultra high-resolution N-body simulations

    CERN Document Server

    Oogi, Taira; Ishiyama, Tomoaki; Kobayashi, Masakazu A R; Makiya, Ryu; Nagashima, Masahiro

    2015-01-01

    We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations. In this study, we assume that a major merger of galaxies triggers cold gas accretion on to a supermassive black hole and quasar activity. Our model can reproduce the downsizing trend of the evolution of quasars. We find that the median mass of quasar host dark matter haloes increases with cosmic time by an order of magnitude from z=4 (a few 1e+11 Msun) to z=1 (a few 1e+12 Msun), and depends only weakly on the quasar luminosity. Deriving the quasar bias through the quasar--galaxy cross-correlation function in the model, we find that the quasar bias does not depend on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. We also show that the quasar bias increas...

  17. Alignment of quasar polarizations with large-scale structures

    CERN Document Server

    Hutsemékers, Damien; Pelgrims, Vincent; Sluse, Dominique

    2014-01-01

    We have measured the optical linear polarization of quasars belonging to Gpc-scale quasar groups at redshift z ~ 1.3. Out of 93 quasars observed, 19 are significantly polarized. We found that quasar polarization vectors are either parallel or perpendicular to the directions of the large-scale structures to which they belong. Statistical tests indicate that the probability that this effect can be attributed to randomly oriented polarization vectors is of the order of 1%. We also found that quasars with polarization perpendicular to the host structure preferentially have large emission line widths while objects with polarization parallel to the host structure preferentially have small emission line widths. Considering that quasar polarization is usually either parallel or perpendicular to the accretion disk axis depending on the inclination with respect to the line of sight, and that broader emission lines originate from quasars seen at higher inclinations, we conclude that quasar spin axes are likely parallel ...

  18. A new sample of quasars to B = 22.0

    Science.gov (United States)

    Marano, B.; Zamorani, G.; Zitelli, V.

    1988-01-01

    A new sample of quasars with complete spectroscopic information down to about 22 mag is presented. The candidate selection and preliminary spectroscopic results are reported. Results are reported from the application of color-color diagrams, grism plates, and variability analysis in the quasar selection. The results on quasar counts, redshift distribution, and luminosity function at high redshift are discussed.

  19. Quasar Classification Using Color and Variability

    CERN Document Server

    Peters, Christina M; Myers, Adam D; Strauss, Michael A; Schmidt, Kasper B; Ivezić, Željko; Ross, Nicholas P; MacLeod, Chelsea L; Riegel, Ryan

    2015-01-01

    We conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. We use a Bayesian quasar selection algorithm (Richards et al. 2004) to identify 35,820 type 1 quasar candidates in a 239 square degree field of the Sloan Digital Sky Survey (SDSS) Stripe 82, using a combination of optical photometry and variability. Color analysis is performed on 5-band single- and multi-epoch SDSS optical photometry to a depth of r ~22.4. From these data, variability parameters are calculated by fitting the structure function of each object in each band with a power law model using 10 to >100 observations over timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type-1 quasars, largely from the SDSS. Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency ...

  20. The UV Properties of SDSS Selected Quasars

    CERN Document Server

    Trammell, G B; Schneider, D P; Richards, G T; Hall, P B; Anderson, S F; Brinkmann, J; Trammell, George B.; Berk, Daniel E. Vanden; Schneider, Donald P.; Richards, Gordon T.; Hall, Patrick B.; Anderson, Scott F.

    2006-01-01

    We present an analysis of the broadband UV/optical properties of z<3.4 quasars matched in the Galaxy Evolution Explorer (GALEX) General Data Release 1 (GR1) and the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Of the 6371 DR3 quasars covered by 204 GR1 tiles, 5380 have near-UV detections, while 3034 have both near-UV and far-UV detections using a matching radius of 7". Most of the DR3 sample quasars are detected in the near-UV until z~1.7, with the near-UV detection fraction dropping to ~50% by z~2. Statistical tests performed on the distributions of non-detections indicate that the optically-selected quasars missed in the UV tend to be optically faint or at high redshift. The GALEX positions are shown to be consistent with the SDSS astrometry to within an rms scatter of 0.6-0.7" in each coordinate, and empirically determined photometric errors from multi-epoch GALEX observations significantly exceed the Poissonian errors quoted in the GR1 object catalogs. The UV-detected quasars are well separated ...

  1. Relativistic redshifts in quasar broad lines

    CERN Document Server

    Tremaine, Scott; Liu, Xin; Loeb, Abraham

    2014-01-01

    The broad emission lines commonly seen in quasar spectra have velocity widths of a few per cent of the speed of light, so special- and general-relativistic effects have a significant influence on the line profile. We have determined the redshift of the broad H-beta line in the quasar rest frame (determined from the core component of the [OIII] line) for over 20,000 quasars from the Sloan Digital Sky Survey DR7 quasar catalog. The mean redshift as a function of line width is approximately consistent with the relativistic redshift that is expected if the line originates in a randomly oriented Keplerian disk that is obscured when the inclination of the disk to the line of sight exceeds ~30-45 degrees, consistent with simple AGN unification schemes. This result also implies that the net line-of-sight inflow/outflow velocities in the broad-line region are much less than the Keplerian velocity when averaged over a large sample of quasars with a given line width.

  2. Feedback in Luminous Obscured Quasars

    CERN Document Server

    Greene, Jenny E; Ho, Luis C; Barth, Aaron J

    2011-01-01

    We use spatially resolved long-slit spectroscopy from Magellan to investigate the extent, kinematics, and ionization structure in the narrow-line regions of 15 luminous, obscured quasars with z<0.5. Increasing the dynamic range in luminosity by an order of magnitude, as well as improving the depth of existing observations by a similar factor, we revisit relations between narrow-line region size and the luminosity and linewidth of the narrow emission lines. We find a slope of 0.22 +/- 0.04 for the power-law relationship between size and luminosity, suggesting that the nebulae are limited by availability of gas to ionize at these luminosities. In fact, we find that the active galactic nucleus is effectively ionizing the interstellar medium over the full extent of the host galaxy. Broad (~300-1000 km/s) linewidths across the galaxies reveal that the gas is kinematically disturbed. Furthermore, the rotation curves and velocity dispersions of the ionized gas remain constant out to large distances, in striking c...

  3. Quasar evolution and gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Cavaliere, A.; Giallongo, E.; Vagnetti, F.; Messina, A.

    1983-06-01

    The paper presents three convergent results concerning the sources in theactive nuclei of quasars and radio galaxies that derive their power fromconversion of gravitational energy. We first derive, for several leading modelsbased on liberation of gravitational energy from mass in a compact supply, thelaws governing the secular change L of the primary power driving the individual sources, and identify their common and key property: L increases, and eventually decreases, linearly or faster with the power itself, so that the associated time scales t/sub s/ = L/Vertical BarLVertical Bar obey dt/sub s/, (L)/dL<0. We then describe a general statistical framework to populate with sources the (luminosity, cosmic time)-plane, based on a continuity equation that embodies a given L. We show how the main features of the populations depend primarily on L, while the memory of the initial details is easily erased. With L as derived above, we obtain basic evolutions of the density (L>0) and of the luminosity (L<0) type, with a global differential character. Finally we compute the full evolution functions, comprising a brightening (L>0) and a dimming (L<0) phase, corresponding to three such models. Sub-Eddington accretion onto a massive black hole from a star cluster that self-destroys by collisions is close to reproduce the general course of the empirical models for the optical QSO population.

  4. Red quasars not so dusty

    CERN Document Server

    Benn, C R; Carballo, R; González-Serrano, J I; Sánchez, S F

    1997-01-01

    Webster et al (1995) claimed that up to 80% of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B-K optical-infrared colours of a sample of flat-spectrum PKS radio QSOs. If such dust is typical of QSOs, it will have rendered invisible most of those which would otherwise been have detected by optical surveys. We used the William Herschel Telescope on La Palma to obtain K infrared images of 54 B3 radio quasars selected at low frequency (mainly steep-spectrum), and we find that although several have very red optical-infrared colours, most of these can be attributed to an excess of light in K rather than a dust-induced deficit in B. We present evidence that some of the infrared excess comes from the light of stars in the host galaxy (some, as previously suggested, comes from synchrotron radiation associated with flat-spectrum radio sources). The B-K colours of the B3 QSOs provide no evidence for a large reddened population. Either the Webster et al QSOs are ...

  5. Detailed Characterization of H_beta emission line profile in low z SDSS quasars

    CERN Document Server

    Zamfir, S; Marziani, P; Dultzin, D

    2009-01-01

    We explore the properties of the H_beta emission line profile in a large, homogeneous and bright sample of N~470 low redshift quasars extracted from Sloan Digital Sky Survey (DR5). We approach the investigation from two complementary directions: composite/median spectra and a set of line diagnostic measures (asymmetry index, centroid shift and kurtosis) in individual quasars. The project is developed and presented in the framework of the so-called 4D Eigenvector 1 (4DE1) Parameter Space, with a focus on its optical dimensions, FWHM(H_beta) and the relative strength of optical FeII (R_FeII=W(FeII4434-4684)/W(H_beta)). We reenforce the conclusion that not all quasars are alike and spectroscopically they do not distribute randomly about an average typical optical spectrum. Our results give further support to the concept of two populations A and B (narrower and broader than 4000 km/s FWHM(H_beta), respectively) that emerged in the context of 4DE1 space. The broad H_beta profiles in composite spectra of Population...

  6. The compact structure of radio-loud broad absorption line quasars

    Science.gov (United States)

    Liu, Y.; Jiang, D. R.; Wang, T. G.; Xie, F. G.

    2008-11-01

    We present the results of EVN+MERLIN very long baseline interferometry (VLBI) polarization observations of eight broad absorption line (BAL) quasars at 1.6 GHz, including four low-ionization BAL quasars (LoBALs) and four high-ionization BAL quasars (HiBALs) with either steep or flat spectra on Very Large Array (VLA) scales. Only one steep-spectrum source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other four steep-spectrum sources and three flat-spectrum sources display either an unresolved image or a core-jet structure on scales of less than 300 pc. In all cases, the marginally resolved core is the dominant radio component. Linear polarization in the cores has been detected in the range of a few to 10 per cent. Polarization, together with high brightness temperatures (from 2 × 109 to 5 × 1010K), suggests a synchrotron origin for the radio emission. There is no apparent difference in the radio morphologies or polarization between low-ionization and high-ionization BAL quasi-stellar objects (QSOs) or between flat- and steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat and steep spectra, and consider a possible evolutionary scenario for BAL QSOs. In this scenario, BAL QSOs are probably a young population of radio sources that are compact steep spectrum or GHz peaked radio source analogues at the low end of radio power.

  7. Time delay and lens redshift for the doubly imaged BAL quasar SBS1520+530

    CERN Document Server

    Burud, I; Courbin, F; Cohen, J G; Magain, P; Jaunsen, A O; Kaas, A A; Faure, C; Letawe, G

    2002-01-01

    We present optical R-band light curves of the gravitationally lensed quasar SBS1520+530 derived from data obtained at the Nordic Optical Telescope. A time delay of 130+/-3 days (1 sigma) is determined from the light curves. In addition, spectra of SBS1520+530 obtained at the Keck Observatory are spatially deconvolved in order to extract the spectrum of the faint lensing galaxy, free of any contamination by the light from the bright quasar images. This spectrum indicates a lens redshift z=0.717, in agreement with one of the absorption systems found in the quasar spectra. The best mass model of the system includes a second nearby galaxy and a cluster of galaxies in addition to the main lensing galaxy. Adopting this model and an Omega=0.3, Lambda=0.7 cosmology, our time-delay measurement yields a Hubble constant of H_0=51+/- 9, km/s/Mpc (1 sigma error).

  8. The Very Extended Ionized Nebula around the Quasar MR2251-178

    CERN Document Server

    Shopbell, P L; Bland-Hawthorn, J

    1999-01-01

    We report the results of deep H-alpha imaging of the ionized gas surrounding the low-redshift (z=0.0638) quasar MR 2251-178 using the TAURUS Tunable Filter (TTF) on the Anglo-Australian Telescope. Our observations reach a 2-sigma detection level of ~5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, more than an order of magnitude deeper than conventional narrowband images previously published on this object. Our data reveal a spiral complex that extends more or less symmetrically over ~200 kpc, making it the largest known quasar nebula. The total mass of ionized gas is 6 x 10^10 solar masses (upper limit), a large fraction of which is in a very faint, diffuse component. The large and symmetric extent of the gaseous envelope favors a model in which the filamentary and diffuse emission arises from a large cloud complex, photoionized by the bright quasar. A crude kinematic analysis reveals relatively smooth rotation, suggesting that the envelope did not originate with a cooling flow, a past merger event, or an interaction wi...

  9. VLBI observations of a flared optical quasar CGRaBS J0809+5341

    CERN Document Server

    An, Tao; Paragi, Zsolt; Frey, Sandor; Gurvits, Leonid I; Gabanyi, Krisztina E

    2016-01-01

    A bright optical flare was detected in the high-redshift ($z=2.133$) quasar CGRaBS J0809+5341 on 2014 April 13. The absolute magnitude of the object reached $-30.0$ during the flare, making it the brightest one (in flaring stage) among all known quasars so far. The 15 GHz flux density of CGRaBS J0809+5341 monitored in the period from 2008 to 2016 also reached its peak at the same time. To reveal any structural change possibly associated with the flare in the innermost radio structure of the quasar, we conducted a pilot very long baseline interferometry (VLBI) observation of CGRaBS J0809+5341 using the European VLBI Network (EVN) at 5 GHz on 2014 November 18, about seven months after the prominent optical flare. Three epochs of follow-up KaVA (Korean VLBI Network and VLBI Exploration of Radio Astrometry Array) observations were carried out at 22 and 43 GHz frequencies from 2015 February 25 to June 4, with the intention of exploring a possibly emerging new radio jet component associated with the optical flare. ...

  10. The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum galaxies. II. Results from the commissioning observations and the pilot surveys

    International Nuclear Information System (INIS)

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg2 from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg2 that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.

  11. The LAMOST survey of background quasars in the vicinity of the Andromeda and Triangulum galaxies. II. Results from the commissioning observations and the pilot surveys

    Energy Technology Data Exchange (ETDEWEB)

    Huo, Zhi-Ying; Bai, Zhong-Rui; Chen, Jian-Jun; Chen, Xiao-Yan; Du, Bing; Jia, Lei; Lei, Ya-Juan [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Liu, Xiao-Wei; Yuan, Hai-Bo [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Xiang, Mao-Sheng; Huang, Yang; Zhang, Hui-Hua [Department of Astronomy, Peking University, Beijing 100871 (China); Yan, Lin [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Chu, Jia-Ru; Chu, Yao-Quan; Hu, Hong-Zhuan [University of Science and Technology of China, Hefei 230026 (China); Cui, Xiang-Qun; Hou, Yong-Hui; Hu, Zhong-Wen; Jiang, Fang-Hua, E-mail: zhiyinghuo@bao.ac.cn [Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042 (China); and others

    2013-06-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg{sup 2} from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg{sup 2} that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local

  12. Dual-frequency VSOP Imaging of a High-redshift Radio Quasar PKS 1402+044

    CERN Document Server

    Yang, J; Lobanov, A; Frey, S; Hong, X Y; Yang, Jun; Gurvits, Leonid; Lobanov, Andrei; Frey, Sandor; Hong, Xiao-Yu

    2006-01-01

    Based on the VLBI Space Observatory Programme (VSOP) observations at 1.6 and 5 GHz, we find that the luminous high-redshift (z=3.215) quasar PKS 1402+044 (J1405+0415) has a pronounced 'core--jet' structure. The jet shows a steeper spectral index and lower brightness temperature with the increase of the distance from the core. The variation of brightness temperature is basically consistent with the shock-in-jet model. Assuming that the jet is collimated by the ambient magnetic field, we estimate the mass of the central object as ~10^9 M_sun. The upper limit of the jet proper motion of PKS 1402+044 is 0.03 mas/yr (~3c) in the east-west direction.

  13. Black-hole masses of distant quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2011-01-01

    A brief overview of the methods commonly used to determine or estimate the black hole mass in quiescent or active galaxies is presented and it is argued that the use of mass-scaling relations is both a reliable and the preferred method to apply to large samples of distant quasars. The method uses...... that the black hole masses are very large, of order 1 to 10 billion solar masses, even at the highest redshifts of 4 to 6. The black holes must build up their mass very fast in the early universe. Yet they do not grow much larger than that: a maximum mass of about 10 billion solar masses is also observed....... Preliminary mass functions of active black holes are presented for several quasar samples, including the Sloan Digital Sky Survey. Finally, common concerns related to the application of the mass scaling relations, especially for high redshift quasars, are briefly discussed....

  14. Detecting the First Quasars with ALMA

    Science.gov (United States)

    Schleicher, Dominik R. G.; Spaans, Marco; Klessen, Ralf S.

    2010-05-01

    We show that ALMA is the first telescope that can probe the dust-obscured central region of quasars at z > 5 with a maximum resolution of ~ 30 pc employing the 18 km baseline. We explore the possibility of detecting the first quasars with ALMA (Schleicher, Spaans, & Klessen 2009). For this purpose, we adopt the Seyfert 2 galaxy NGC 1068 as a reference system and calculate the expected fluxes if this galaxy were placed at high redshift. This choice is motivated by the detailed observations available for this system and the absence of any indication for an evolution in metallicity in high-redshift quasars. It is a conservative choice due to the moderate column densities in NGC 1068, leading to moderate fluxes.

  15. General relativitistic theory of quasars, 1

    CERN Document Server

    Zakir, Z

    2000-01-01

    In the paper physics/0007003 it was shown that after a correct definition of the relations between observables in general relativity a horizon and a singularity disappear. The general relativity in physical variables really predicts an existence of supercompact relativistic stars and relativistic galactic nuclei with (light and heavy) barionic and quark contents instead of unphysical black holes. They have the radii near the gravitational radii and emit the spectral lines with high redshifts and the energetic (X- and gamma) photons. The quasars can be naturally interpreted as such relativistic supercompact objects and their high redshifts explained mainly as a gravitational redshift. The existing of the second mechanism of redshift in addition to the Doppler shift leads to a normalization of all parameters of quasars as the compact galactic nuclei. In principle new consequence of general relativity is a prediction that some of quasars may be the relativistic stars in the Galaxy. A short time variability of su...

  16. Evolution of a Powerful Radio Loud Quasar 3C186 and its Impact on the Cluster Environment at z=1

    CERN Document Server

    Siemiginowska, Aneta; Burke, Doug; Bechtold, Jill; Cheung, C C; LaMassa, Stephanie; Worrall, Diana M

    2007-01-01

    X-ray cluster emission has been observed mainly in clusters with "inactive" cD galaxies (L_bol ~1E40-1E43erg/sec), which do not show signs of accretion onto a SMBH. Our recent Chandra discovery of ~100kpc scale diffuse X-ray emission revealed the presence of an X-ray cluster associated with the radio loud quasar 3C186 at redshift z=1.1 and suggests interactions between the quasar and the cluster. In contrast to the majority of X-ray clusters the 3C186 cluster contains a quasar in the center whose radiative power alone exceeds that which would be needed to quench the cluster cooling. We present the Chandra X-ray data and new deep radio and optical images of this cluster. The 3C186 quasar is a powerful Compact Steep Spectrum radio source expanding into the cluster medium. The 2arcsec radio jet is unresolved in the Chandra observation, but its direction is orthogonal to the elliptical surface brightness of the cluster. The radio data show the possible presence of old radio lobes on 10 arcsec scale in the directi...

  17. The Extreme Ultraviolet Variability of Quasars

    Science.gov (United States)

    Punsly, Brian; Marziani, Paola; Zhang, Shaohua; Muzahid, Sowgat; O’Dea, Christopher P.

    2016-10-01

    We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500–920 Å) of high-luminosity quasars using Hubble Space Telescope (HST) (low to intermediate redshift sample) and Sloan Digital sky Survey (SDSS) (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling time between observations in the quasar rest frame is \\gt 2× {10}7 {{s}} compared to \\lt 1.5× {10}7 s. Based on an excess variance analysis, for time intervals \\lt 2× {10}7 {{s}} in the quasar rest frame, 10% of the quasars (4/40) show evidence of EUV variability. Similarly, for time intervals \\gt 2× {10}7 {{s}} in the quasar rest frame, 55% of the quasars (21/38) show evidence of EUV variability. The propensity for variability does not show any statistically significant change between 2.5× {10}7 {{s}} and 3.16× {10}7 {{s}} (1 year). The temporal behavior is one of a threshold time interval for significant variability as opposed to a gradual increase on these timescales. A threshold timescale can indicate a characteristic spatial dimension of the EUV region. We explore this concept in the context of the slim disk models of accretion. We find that for rapidly spinning black holes, the radial infall time to the plunge region of the optically thin surface layer of the slim disk that is responsible for the preponderance of the EUV flux emission (primarily within 0–7 black hole radii from the inner edge of the disk) is consistent with the empirically determined variability timescale.

  18. Understanding the near infrared spectrum of quasars

    Science.gov (United States)

    Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena; Mateos, Silvia

    2016-08-01

    The rest-frame near infrared (NIR) is a key spectral range for understanding the physics of AGN, but progress has been hindered by the difficulty in defining the NIR spectrum of the accretion disk and removing contamination from stellar emission in the host galaxy. In this talk I will present the analysis of a sample of 85 luminous (L3µm>10^45.5 erg/s) quasars with rest-frame NIR spectroscopy from AKARI and Spitzer/IRS. Their high luminosity allows a direct determination of the NIR shape of the quasar spectrum clean from host galaxy emission. We find that the entire UV-to-MIR SED can be accurately reproduced with a semi-empirical disk+dust model that uses a single template for the accretion disk and two blackbody components (hot and warm) for the dust. The observed diversity in individual SEDs can be accounted for by varying levels of extinction affecting the disk component and differences in the relative luminosities of the disk and dust components. We present a new quasar template [0.1-10µm] as well as separate templates for the disk and dust components, and conclude that previous templates based on less luminous quasars suffer from contamination by stellar emission in the host galaxy, which accounts for up to ~30% of the flux at 1µm. We also perform the first ever measurement of the Paschen_α emission in a large sample of luminous quasars and find that the Paschen_α to optical continuum luminosity ratio is boosted in our sample compared to less luminous quasars.

  19. Optical Spectrophotometric Monitoring of Fermi/LAT Bright Sources

    CERN Document Server

    Patiño-Álvarez, V; León-Tavares, J; Valdés, J R; Carramiñana, A; Carrasco, L; Torrealba, J

    2013-01-01

    We describe an ongoing optical spectrophotometric monitoring program of a sample of Fermi/LAT bright sources showing prominent and variable {\\gamma}-ray emission, with the 2.1m telescope at Observatorio Astrof\\'isico Guillermo Haro (OAGH) located in Cananea, Sonora, M\\'exico. Our sample contains 11 flat spectrum radio quasars (FSRQ) and 1 Narrow Line Seyfert 1 (NLSy1) galaxy. Our spectroscopic campaign will allow us to study the spectroscopic properties (FWHM, EW, flux) of broad-emission lines in the optical (e.g. H{\\beta}) and mid-UV (e.g. Mg II {\\lambda}2800) regimes, depending on the redshift of the source. The cadence of the broad emission lines monitoring is about five nights per month which in turn will permit us to explore whether there is a correlated variability between broad emission line features and high levels of {\\gamma}-ray emission.

  20. Quasar polarization with ultralight (pseudo-)scalars

    Indian Academy of Sciences (India)

    Ki-Young choi; Subhayan Mandal; Chang Sub Shin

    2016-01-01

    Recently, it was shown that the absence of circular polarization of visible light from quasars severely constrains the interpretation of axion-like particles (ALPs) as a solution for the generation of linear polarization. Furthermore, the new observation of linear polarization in radio wavelength from quasars, similar to the earlier observation performed in the optical bands, makes the ALPs scenario inconsistent with at least one of the two observations. In this study, we extend this scenario by including more scalars. We find that the effects from scalar and pseudoscalar neutralize each other, thereby suppressing the circular polarization, while preserving consistent linear polarization, as observed in both the visible and radio wave bands.

  1. Interferometer observations of quasars from the Jodrell Bank 966-MHz survey

    International Nuclear Information System (INIS)

    Radio observations are reported of the 68 quasars with blue magnitudes < or =19.0 identified in the Jodrell Bank 966-MHz survey. The observations were made with the Green Bank interferometer at 2695 MHz with baselines ranging from 300 m to 35 km. Model brightness distributions are presented consisting of one to four elliptical Gaussian components. A limiting resolution of 0.1 arcsec was obtained in the best cases. For radio sources with steep spectra, angular sizes ranged from <0.2 to 85 arcsec. Only two of the sources with steep radio spectra were unresolved. The median angular size for the entire sample is 8 arcsec. For quasars larger than 10 arcsec, the structures can almost always be described in triple. Twenty-nine of the 30 such sources have outer lobes on either side of the optical source and 24 of the 30 have detectable central components. The ratio of the flux densities of the outer lobes varies over a wide range but has a median value of 1.8. The ratio of the flux density of the central component to the total flux density at 2695 MHz ranges from 1% to 95%, with a median value near 10%. The existence of triple structure in the vast majority of quasars, along the with failure to detect central components in blank field sources, suggests a close connection between the nuclear activity in the radio and optical regions of the spectrum. It is also consistent with a picture in which the difference between blank fields and quasars is just transient activity in the nucleus of a distant parent galaxy

  2. Distinctive 21-cm structures of the first stars, galaxies and quasars

    Science.gov (United States)

    Yajima, Hidenobu; Li, Yuexing

    2014-12-01

    Observations of the redshifted 21-cm line with forthcoming radio telescopes promise to transform our understanding of the cosmic reionization. To unravel the underlying physical process, we investigate the 21-cm structures of three different ionizing sources - Population (Pop) III stars, the first galaxies and the first quasars - by using radiative transfer simulations that include both ionization of neutral hydrogen and resonant scattering of Lyα photons. We find that Pop III stars and quasars produce a smooth transition from an ionized and hot state to a neutral and cold state, because of their hard spectral energy distribution with abundant ionizing photons, in contrast to the sharp transition in galaxies. Furthermore, Lyα scattering plays a dominant role in producing the 21-cm signal because it determines the relation between hydrogen spin temperature and gas kinetic temperature. This effect, also called Wouthuysen-Field coupling, depends strongly on the ionizing source. It is strongest around galaxies, where the spin temperature is highly coupled to that of the gas, resulting in extended absorption troughs in the 21-cm brightness temperature. However, in the case of Pop III stars, the 21-cm signal shows both emission and absorption regions around a small H II bubble. For quasars, a large emission region in the 21-cm signal is produced, and the absorption region decreases as the size of the H II bubble becomes large due to the limited travelling time of photons. We predict that future surveys from large radio arrays, such as the Murchison Widefield Array, the Low Frequency Array and the Square Kilometre Array, might be able to detect the 21-cm signals of primordial galaxies and quasars, but possibly not those of Pop III stars, because of their small angular diameters.

  3. VLBI observations of flared optical quasar CGRaBS J0809+5341

    Science.gov (United States)

    An, Tao; Cui, Yu-Zhu; Paragi, Zsolt; Frey, Sándor; Gurvits, Leonid I.; Gabányi, Krisztina É.

    2016-08-01

    A bright optical flare was detected in the high-redshift (z = 2.133) quasar CGRaBS J0809+5341 on 2014 April 13. The absolute magnitude of the object reached -30.0 during the flare, making it the brightest one (in flaring stage) among all known quasars so far. The 15-GHz flux density of CGRaBS J0809+5341 monitored in the period from 2008 to 2016 also reached its peak at the same time. To reveal any structural change possibly associated with the flare in the innermost radio structure of the quasar, we conducted a pilot very long baseline interferometry (VLBI) observation of CGRaBS J0809+5341 using the European VLBI Network (EVN) at 5 GHz on 2014 November 18, about seven months after the prominent optical flare. Three epochs of follow-up KaVA (Korean VLBI Network and VLBI Exploration of Radio Astrometry Array) observations were carried out at 22- and 43-GHz frequencies from 2015 February 25 to June 4, with the intention of exploring a possibly emerging new radio jet component associated with the optical flare. However, these high-resolution VLBI observations revealed only the milliarcsecond-scale compact "core" that was known in the quasar from earlier VLBI images, and showed no sign of any extended jet structure. Neither the size nor the flux density of the "core" changed considerably after the flare, according to our VLBI monitoring. The results suggest that any putative radio ejecta associated with the major optical and radio flare could not yet be separated from the "core" component, or the newly-born jet was short-lived.

  4. Half-megasecond Chandra spectral imaging of the hot circumgalactic nebula around quasar MRK 231

    Energy Technology Data Exchange (ETDEWEB)

    Veilleux, S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Teng, S. H. [Observational Cosmology Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Rupke, D. S. N. [Department of Physics, Rhodes College, Memphis, TN 38112 (United States); Maiolino, R. [Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Sturm, E., E-mail: veilleux@astro.umd.edu [Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany)

    2014-08-01

    A deep 400 ks ACIS-S observation of the nearest quasar known, Mrk 231, is combined with archival 120 ks data to carry out the first ever spatially resolved spectral analysis of a hot X-ray-emitting circumgalactic nebula around a quasar. The 65 × 50 kpc X-ray nebula shares no resemblance with the tidal debris seen at optical wavelengths. One notable exception is the small tidal arc ∼3.5 kpc south of the nucleus where excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are detected, consistent with star formation and its associated alpha-element enhancement, respectively. An X-ray shadow is also detected at the location of the 15 kpc northern tidal tail. The hard X-ray continuum emission within ∼6 kpc of the center is consistent with being due entirely to the bright central active galactic nucleus. The soft X-ray spectrum of the outer (≳6 kpc) portion of the nebula is best described as the sum of two thermal components with temperatures ∼3 and ∼8 million K and spatially uniform super-solar alpha-element abundances, relative to iron. This result implies enhanced star formation activity over ∼10{sup 8} yr, accompanied by redistribution of the metals on a large scale. The low-temperature thermal component is not present within ∼6 kpc of the nucleus, suggesting extra heating in this region from the circumnuclear starburst, the central quasar, or the optically identified ≳3 kpc quasar-driven outflow. The soft X-ray emission is weaker in the western quadrant, coincident with a deficit of Hα and some of the largest columns of neutral gas outflowing from the nucleus. Shocks may heat the gas to high temperatures at this location, consistent with the tentative ∼2σ detection of extended Fe XXV 6.7 keV line emission.

  5. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    CERN Document Server

    La Plante, Paul

    2015-01-01

    We introduce a new project to understand helium reionization using fully coupled $N$-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium (IGM) as a result of reionization and make predictions about the Lyman-$\\alpha$ forest and baryon temperature-density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models include two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function (QLF) given a halo catalog from an $N$-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurem...

  6. Photocentric variability of quasars caused by variations in their inner structure: consequences for Gaia measurements

    Science.gov (United States)

    Popović, L. Č.; Jovanović, P.; Stalevski, M.; Anton, S.; Andrei, A. H.; Kovačević, J.; Baes, M.

    2012-02-01

    Context. We study the photocenter position variability caused by variations in the quasar inner structure. We consider the variability in the accretion disk emissivity and torus structure variability caused by the different illumination by the central source. We discuss the possible detection of these effects by Gaia. Observations of the photocenter variability in two AGNs, SDSS J121855+020002 and SDSS J162011+1724327 have been reported and discussed. Aims: For variations in the quasar inner structure, we explore how much this effect can affect the position determination and whether it can (or not) be detected with the Gaia mission. Methods: We use models of (a) a relativistic disk, including the perturbation that can increase the brightness of part of the disk, and consequently offset the photocenter position, and (b) a dusty torus that absorbs and re-emits the incoming radiation from the accretion disk (central continuum source). We estimate the value of the photocenter offset caused by these two effects. Results: We found that perturbations in the inner structure can cause a significant offset to the photocenter. This offset depends on the characteristics of both the perturbation and accretion disk and on the structure of the torus. In the case of the two considered QSOs, the observed photocenter offsets cannot be explained by variations in the accretion disk and other effects should be considered. We discuss the possibility of exploding stars very close to the AGN source, and also that there are two variable sources at the center of these two AGNs that may indicate a binary supermassive black hole system on a kpc (pc) scale. Conclusions: The Gaia mission seems to be very promising, not only for astrometry, but also for exploring the inner structure of AGNs. We conclude that variations in the quasar inner structure can affect the observed photocenter (by up to several mas). There is a chance to observe such an effect in the case of bright and low-redshift QSOs.

  7. STRUCTURE FUNCTION ANALYSIS OF LONG-TERM QUASAR VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    de Vries, W; Becker, R; White, R; Loomis, C

    2004-11-15

    In our second paper on long-term quasar variability, we employ a much larger database of quasars than in de Vries, Becker & White. This expanded sample, containing 35,165 quasars from the Sloan Digital Sky Survey Data Release 2, and 6,413 additional quasars in the same area of the sky taken from the 2dF QSO Redshift Survey, allows us to significantly improve on our earlier conclusions. As before, all the historic quasar photometry has been calibrated onto the SDSS scale by using large numbers of calibration stars around each quasar position. We find the following: (1) the outbursts have an asymmetric light-curve profile, with a fast-rise, slow-decline shape; this argues against a scenario in which micro-lensing events along the line-of-sight to the quasars are dominating the long-term variations in quasars; (2) there is no turnover in the Structure Function of the quasars up to time-scales of {approx}40 years, and the increase in variability with increasing time-lags is monotonic and constant; and consequently, (3) there is not a single preferred characteristic outburst time-scale for the quasars, but most likely a continuum of outburst time-scales, (4) the magnitude of the quasar variability is a function of wavelength: variability increases toward the blue part of the spectrum, (5) high-luminosity quasars vary less than low-luminosity quasars, consistent with a scenario in which variations have limited absolute magnitude. Based on this, we conclude that quasar variability is intrinsic to the Active Galactic Nucleus, is caused by chromatic outbursts/flares with a limited luminosity range and varying time-scales, and which have an overall asymmetric light-curve shape. Currently the model that has the most promise of fitting the observations is based on accretion disk instabilities.

  8. THE LARGE SKY AREA MULTI-OBJECT FIBER SPECTROSCOPIC TELESCOPE QUASAR SURVEY: QUASAR PROPERTIES FROM THE FIRST DATA RELEASE

    Energy Technology Data Exchange (ETDEWEB)

    Ai, Y. L.; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian; Wang, Feige; Guo, Rui; Dong, Xiaoyi [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Zuo, Wenwen; Shen, S.-Y. [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Zhang, Y.-X.; Yuan, H.-L.; Song, Y.-H.; Yang, M.; Wu, H.; Shi, J.-R.; He, B.-L.; Lei, Y.-J.; Li, Y.-B. [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences 100012, Beijing (China); Wang, Jianguo; Dong, Xiaobo, E-mail: aiyl@pku.edu.cn [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); and others

    2016-02-15

    We present preliminary results of the quasar survey in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes the pilot survey and the first year of the regular survey. There are 3921 quasars reliably identified, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with a highest z of 4.83. We compile emission line measurements around the Hα, Hβ, Mg ii, and C iv regions for the new quasars. The continuum luminosities are inferred from SDSS photometric data with model fitting, as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, with flags indicating the selection methods, and broad absorption line quasars. The catalog and spectra for these quasars are also available. Of the 3921 quasars, 28% are independently selected with optical–infrared colors, indicating that the method is quite promising for the completeness of the quasar survey. LAMOST DR1 and the ongoing quasar survey will provide valuable data for studies of quasars.

  9. MiNDSTEp differential photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756: Microlensing and a new time delay

    CERN Document Server

    Giannini, E; Wambsganß, J; Alsubai, K; Andersen, J M; Anguita, T; Bozza, V; Bramich, D M; Browne, P; Novati, S Calchi; Damerdji, Y; Diehl, C; Dodds, P; Dominik, M; Elyiv, A; Fang, X; Jaimes, R Figuera; Finet, F; Gerner, T; Gu, S; Hardis, S; Harpsøe, K; Hinse, T C; Hornstrup, A; Hundertmark, M; Jessen-Hansen, J; Jørgensen, U G; Juncher, D; Kains, N; Kerins, E; Korhonen, H; Liebig, C; Lund, M N; Lundkvist, M S; Maier, G; Mancini, L; Masi, G; Mathiasen, M; Penny, M; Proft, S; Rabus, M; Rahvar, S; Ricci, D; Scarpetta, G; Sahu, K; Schäfer, S; Schönebeck, F; Skottfelt, J; Snodgrass, C; Southworth, J; Surdej, J; Tregloan-Reed, J; Vilela, C; Wertz, O; Zimmer, F

    2016-01-01

    We present V and R photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. The quasar WFI2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of $\\Delta t= 7.6\\pm1.8$ days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI2033-4723 and HE0047-1756 become bluer when brighter, which is consisten...

  10. Theoretical spectroscopy of quasars within Karlsson's law

    CERN Document Server

    Moret-Bailly, Jacques

    2016-01-01

    The law introduced by Karlsson in spectroscopy of low-redshift quasars involves the Lyman spectrum of hydrogen atoms. Thus, it appears necessary to study the concepts introduced by a standard spectroscopy of quasars, studied here, with those deducted from $\\Lambda$-CDM.A visible absorption of a sharp and saturated spectral line in a gas requires a long path without perturbations as collisions or cosmological redshift. Spectra of absorbed, saturated lines of quasars obeying Karlsson's law mainly result from interactions of natural, thermal light radiated by quasar with relatively cold, low presure atomic hydrogen. These lines are produced by three processes: a) A conventional absorption in a relatively cold gas produces a set of lines; b) These lines are multiplied by absorption after fundamental 3K or 4K redshifts, where K is Karlsson's constant: Spectra show that redshifts 3K (or 4K) exactly bring absorbed Lyman beta (or gamma) line on Lyman alpha: redshift almost disappears, and gas lines are intensely abso...

  11. Quasar Mass Functions Across Cosmic Time

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2010-01-01

    I present mass functions of actively accreting black holes detected in different quasar surveys which in concert cover a wide range of cosmic history. I briefly address what we learn from these mass functions. I summarize the motivation for such a study and the methods by which we determine black...... hole masses....

  12. The Extreme Ultraviolet Variability of Quasars

    CERN Document Server

    Punsly, Brian; Zhang, Shaohua; Muzahid, Sowgat; O'Dea, Christopher P

    2016-01-01

    We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500 - 920 $\\AA$) of high luminosity quasars using HST (low to intermediate redshift sample) and SDSS (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling time between observations in the quasar rest frame is $> 2\\times 10^{7}$ sec compared to $2\\times 10^{7}$ sec in the quasar rest frame, $55\\%$ of the quasars (21/38) show evidence of EUV variability. The propensity for variability does not show any statistically significant change between $2.5\\times 10^{7}$ sec and $3.16\\times 10^{7}$ sec (1 yr). The temporal behavior is one of a threshold time interval for significant variability as opposed to a gradual increase on these time scales. A threshold time scale can indicate a characteristic spatial dimension of the EUV region. We explore this concept in the context of the slim disk models of accretion. We find that for rapidly spinning black holes, the radial infall...

  13. A Spectacular Post-Starburst Quasar

    CERN Document Server

    Brotherton, M S; Stanford, S A; Smith, R J; Boyle, B J; Miller, L; Shanks, T; Croom, S M; Filippenko, A V; Breugel, Wil van; Miller, Lance; Filippenko, Alexei V.

    1999-01-01

    We report the discovery of a spectacular ``post-starburst quasar'' UN J1025-0040 (B=19; z=0.634). The optical spectrum is a chimera, displaying the broad Mg II emission line and strong blue continuum characteristic of quasars, but is dominated in the red by a large Balmer jump and prominent high-order Balmer absorption lines indicative of a substantial young stellar population at similar redshift. Stellar synthesis population models show that the stellar component is consistent with a 400 Myr old instantaneous starburst with a mass of less than or about 10^{11} solar masses. A deep, K_s-band image taken in 0.5 arcsec seeing shows a point source surrounded by asymmetric extended fuzz. Approximately 70% of the light is unresolved, the majority of which is expected to be emitted by the starburst. While starbursts and galaxy interactions have been previously associated with quasars, no quasar ever before has been seen with such an extremely luminous young stellar population.

  14. Quasar Astrophysics with the Space Interferometry Mission

    Science.gov (United States)

    Unwin, Stephen; Wehrle, Ann; Meier, David; Jones, Dayton; Piner, Glenn

    2007-01-01

    Optical astrometry of quasars and active galaxies can provide key information on the spatial distribution and variability of emission in compact nuclei. The Space Interferometry Mission (SIM PlanetQuest) will have the sensitivity to measure a significant number of quasar positions at the microarcsecond level. SIM will be very sensitive to astrometric shifts for objects as faint as V = 19. A variety of AGN phenomena are expected to be visible to SIM on these scales, including time and spectral dependence in position offsets between accretion disk and jet emission. These represent unique data on the spatial distribution and time dependence of quasar emission. It will also probe the use of quasar nuclei as fundamental astrometric references. Comparisons between the time-dependent optical photocenter position and VLBI radio images will provide further insight into the jet emission mechanism. Observations will be tailored to each specific target and science question. SIM will be able to distinguish spatially between jet and accretion disk emission; and it can observe the cores of galaxies potentially harboring binary supermassive black holes resulting from mergers.

  15. Quasar feedback revealed by giant molecular outflows

    CERN Document Server

    Feruglio, Chiara; Piconcelli, Enrico; Menci, Nicola; Aussel, Herve'; Lamastra, Alessandra; Fiore, Fabrizio

    2010-01-01

    In the standard scenario for galaxy evolution the transformation of young star-forming galaxies into red bulge-dominated spheroids, where star formation has been quenched, is often explained by invoking a strong negative feedback generated by accretion onto a central super-massive black hole. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead to the black hole "suicide" for starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, since outflows previously observed in quasars are associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occur in the central regions. We used the IRAM PdBI to observe the CO(1-0) transition in Mrk 231, the closest quasar known. We detect broad wings of the CO line, with velocities up to 750 km/s and spatially resolved on the kpc scale. Such broad CO wings trace a giant molecular o...

  16. The Physics Program for the QUASAR facility

    Science.gov (United States)

    Gates, D. A.; Lazerson, S. A.; Neilson, G. H.; Zarnstorff, M.; Schmitz, O.; Frerichs, H.

    2014-10-01

    The QUASi-Axisymmetric Research (QUASAR) stellarator is a new facility which can solve two critical problems for fusion, disruptions and steady-state, and which provides new insights into the role of symmetry in plasma confinement. The principle of quasi-axisymmetry will be used in QUASAR to study how tokamak-like systems can be made disruption-free and steady-state with low recirculating power, while also improving upon features of tokamaks, such as; stable at high pressure with high confinement, and scalable to a compact reactor. The two large stellarator experiments - LHD and W7-X - are pioneering facilities capable of developing 3D physics understanding at large scale and for very long pulses. The QUASAR design is unique in being QA and optimized for confinement, stability, and moderate aspect ratio (4.5). Important elements of the physics program for QUASAR are: establishing the physics basis of the design by demonstrating stable operation at high- β simultaneous with good neoclassical confinement, understanding the concomitant turbulent transport, and understanding the dependence of the underlying transport on magnetic geometry. An additional important element of the program will be understanding the physics characteristics of a QA stellarator with an high flux expansion ergodic edge. This work supported by DoE Contract No. DEAC02-76CH03073.

  17. Giant scattering cones in obscured quasars

    CERN Document Server

    Obied, Georges; Wylezalek, Dominika; Liu, Guilin

    2015-01-01

    We analyze Hubble Space Telescope observations of scattering regions in 20 luminous obscured quasars at $0.24quasar hosts' star formation rates. Modeling these regions as illuminated dusty cones, we estimate the radial density distributions of the interstellar medium as well as the geometric properties of circumnuclear quasar obscuration -- inclinations and covering factors. Small derived opening angles (median half-angle and standard deviation 27\\dg$\\pm$9\\dg) are inconsistent with a 1:1 type 1 / type 2 ratio. We suggest that quasar obscuration is patchy and that the observer has a $\\sim 40\\%$ chan...

  18. Galaxy Zoo : 'Hanny's Voorwerp', a quasar light echo?

    CERN Document Server

    Lintott, Chris; Keel, William; van Arkel, Hanny; Bennert, Nicola; Edmondson, Edward; Thomas, Daniel; Smith, Daniel; Herbert, Peter; Jarvis, Matt; Virani, Shanil; Andreescu, Dan; Bamford, Steven; Land, Kate; Murray, Phil; Nichol, Robert; Raddick, Jordan; Slosar, Anze; Szalay, Alex; Vandenberg, Jan

    2009-01-01

    We report the discovery of an unusual object near the spiral galaxy IC 2497, discovered by visual inspection of the Sloan Digital Sky Survey (SDSS) as part of the Galaxy Zoo project. The object, known as Hanny's Voorwerp, is bright in the SDSS g band due to unusually strong OIII 4959-5007 emission lines. We present the results of the first targeted observations of the object in the optical, UV and X-ray, which show that the object contains highly ionized gas. Although the line ratios are similar to extended emission-line regions near luminous AGN, the source of this ionization is not apparent. The emission-line properties, and lack of x-ray emission from IC 2497, suggest either a highly obscured AGN with a novel geometry arranged to allow photoionization of the object but not the galaxy's own circumnuclear gas, or, as we argue, the first detection of a quasar light echo. In this case, either the luminosity of the central source has decreased dramatically or else the obscuration in the system has increased wit...

  19. QUASAR SELECTION BASED ON PHOTOMETRIC VARIABILITY

    International Nuclear Information System (INIS)

    We develop a method for separating quasars from other variable point sources using Sloan Digital Sky Survey (SDSS) Stripe 82 light-curve data for ∼ 10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by a damping timescale, τ, and an asymptotic amplitude (structure function), SF∞. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the τ information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C = 90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E = 80% when imposing a lower limit on τ. With the aid of color selection, the purity can be further boosted to 96%, with C = 93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). For a typical (simulated) LSST cadence over 10 years and a photometric accuracy of 0.03 mag (achieved at i ∼ 22), C is expected to be 88% for a simple sample selection criterion of >100 days. In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.

  20. An X-shooter composite of bright 1 < z < 2 quasars from UV to infrared

    CERN Document Server

    Selsing, Jonatan; Christensen, Lise; Krogager, Jens-Kristian

    2016-01-01

    Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1 < z < 2.1 selected from the Sloan Digital Sky Survey (SDSS). The observations with X-shooter simultaneously cover ultraviolet (UV) to near- infrared (NIR) light, which ensures that the composite spectrum covers the full rest-frame range from Ly$\\beta$ to 11350 $\\AA$ without any significant host contamination. Assuming a power-law continuum for the composite we find a spectral slope of $\\alpha_\\lambda$ = 1.70+/-0.01, which is steeper than previously found in the literature. We attribute the differences to ou...

  1. Soft X-ray Variability of the Bright Quasar 3C273

    Indian Academy of Sciences (India)

    Chulhee Kim

    2001-12-01

    We present the results from ROSAT observations of 3C273 in the soft X-ray band. The light variation of 3C273 was investigated for three different energy bands of soft, medium, and hard. The maximum variability with a factor of 2 for 551 dayswas confirmed at all three different bands. This appears to be a periodic variation within the period of roughly 6 months. However, the short-term or micro variation was not so distinct and the light variation of each band did not show any correlation between them. The hardness ratio for hard and soft bands shows irregular variation but there was no correlation between them. There is no distinct variation of the photon index in the case of simple power law model fitting. For power law + free absorption model fitting, the average photon index () is 2.08.

  2. Similarity of ionized gas nebulae around unobscured and obscured quasars

    Science.gov (United States)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.

    2014-08-01

    Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper, we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III] λ5007 Å emission line. We find that ionized gas nebulae extend out to ˜13 kpc from the quasar, that they are smooth and round, and that their kinematics are inconsistent with gas in dynamical equilibrium with the host galaxy. The observed morphological and kinematic properties are strikingly similar to those of ionized gas around obscured (type 2) quasars with matched [O III] luminosity, with marginal evidence that nebulae around unobscured quasars are slightly more compact. Therefore, in samples of obscured and unobscured quasars carefully matched in [O III] luminosity, we find support for the standard geometry-based unification model of active galactic nuclei, in that the intrinsic properties of the quasars, of their hosts and of their ionized gas appear to be very similar. Given the apparent ubiquity of extended ionized regions, we are forced to conclude that either the quasar is at least partially illuminating pre-existing gas or that both samples of quasars are seen during advanced stages of quasar feedback. In the latter case, we may be biased by our [O III]-based selection against quasars in the early `blow-out' phase, for example due to dust obscuration.

  3. Multiwavelength observations of the γ-ray flaring quasar S4 1030+61 in 2009-2014

    Science.gov (United States)

    Kravchenko, E. V.; Kovalev, Y. Y.; Hovatta, T.; Ramakrishnan, V.

    2016-11-01

    We present a study of the parsec-scale multifrequency properties of the quasar S4 1030+61 during a prolonged radio and γ-ray activity. Observations were performed within Fermi γ-ray telescope, Owens Valley Radio Observatory 40-m telescope and MOJAVE Very Long Baseline Array (VLBA) monitoring programmes, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24 and 43 GHz, which were triggered by the bright γ-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4 ± 0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and γ-ray emission implies a spatial separation between emitting regions at these bands of about 12 pc and locates the γ-ray emission within a parsec from the central engine. We detected changes in the value and direction of the linear polarization and the Faraday rotation measure. The value of the intrinsic brightness temperature of the core is above the equipartition state, while its value as a function of distance from the core is well approximated by the power law. Altogether these results show that the radio flaring activity of the quasar is accompanied by injection of relativistic particles and energy losses at the jet base, while S4 1030+61 has a stable, straight jet well described by standard conical jet theories.

  4. The cosmological evolution of flat-spectrum quasars

    International Nuclear Information System (INIS)

    The spatial distribution and luminosity functions of a complete sample of quasars from the +- 40 declination strip of the Parkes 2.7-GHz survey have been investigated. The luminosity-volume (V/Vsub(m)) test strongly suggests that the flat-spectrum quasars which dominate the sample have an evolutionary history different from that of the steep-spectrum quasars which dominate the 3CR and 4C samples investigated previously. The bivariate luminosity function for the flat-spectrum quasars shows the same strong correlation between radio and optical luminosities exhibited by steep-spectrum quasars. The results of the luminosity-volume test considered in conjunction with radio structures, spectra, and source counts, lead to the tentative suggestion that the cosmological evolution of radio-active quasars is confined to those with extended radio structures. (author)

  5. Weighing obscured and unobscured quasar hosts with the CMB

    CERN Document Server

    DiPompeo, M A; Hickox, R C; Geach, J E; Holder, G; Hainline, K N; Hall, S W

    2014-01-01

    We cross-correlate a cosmic microwave background (CMB) lensing map with the projected space densities of quasars to measure the bias and halo masses of a quasar sample split into obscured and unobscured populations, the first application of this method to distinct quasar subclasses. Several recent studies of the angular clustering of obscured quasars have shown that these objects likely reside in higher-mass halos compared to their unobscured counterparts. This has important implications for models of the structure and geometry of quasars, their role in growing supermassive black holes, and mutual quasar/host galaxy evolution. However, the magnitude and significance of this difference has varied from study to study. Using data from \\planck, \\wise, and SDSS, we follow up on these results using the independent method of CMB lensing cross-correlations. The region and sample are identical to that used for recent angular clustering measurements, allowing for a direct comparison of the CMB-lensing and angular clust...

  6. Multi-wavelength Monitoring of Lensed Quasars: Deciphering Quasar Structure at Micro-arcseconds Scales

    Science.gov (United States)

    Mosquera, Ana; Morgan, Christopher W.; Kochanek, Christopher S.; Dai, Xinyu; Chen, Bin; MacLeod, Chelsea Louise; Chartas, George

    2016-01-01

    Microlensing in multiply imaged gravitationally lensed quasars provides us with a unique tool to zoom in on the structure of AGN and explore their physics in more detail. Microlensing magnification, caused primarily by stars and white dwarfs close to the line of sight towards the lensed quasar images, is seen as uncorrelated flux variations due to the relative motions of the quasar, the lens, its stars, and the observer, and it depends on the structural and dynamical properties of the source and the lens. Since the magnification depends upon the size of the source, we can use microlensing to measure the size of quasar emission regions. In essence, the amplitude of the microlensing variability encodes the source size, with smaller sources showing larger variability amplitudes. Using state of the art microlensing techniques, our team has performed pioneering research in the field based on multi-wavelength space and ground-based observations. Among the most remarkable results, using Chandra observations we have set the first quantitative constraints on the sizes of the X-ray emission regions of quasars. In this work l briefly describe the methodology, the results from our previous multi-wavelength monitoring programs, and the next frontier of exploring the dependence of the structure of the X-ray emission regions on black hole mass and X-ray energy.

  7. Optical structure in some low-redshift quasars

    International Nuclear Information System (INIS)

    Electronographic observations of seven quasars in the redshift range z = 0.2 to 0.4 have been obtained in up to three colours. Five of the quasars are shown to have non-stellar images on R plates but in no case is a quasar image distinguishable from a star image on a B plate. These measurements are shown to be consistent with the presence of underlying galaxies. (author)

  8. Quasar Apparent Proper Motion Observed by Geodetic VLBI Networks

    OpenAIRE

    D. S. MacMillan

    2003-01-01

    In our standard geodetic VLBI solutions, we estimate the positions of quasars assuming that their positions do not vary in time. However, in solutions estimating proper motion, a significant number of quasars show apparent proper motion greater than 50 uas/yr. For individual quasars, there are source structure effects that cause apparent proper motion. To examine how coherent the pattern of apparent proper motion is over the sky, we have estimated the vector spherical harmonic components of t...

  9. Structure Function Analysis of Long Term Quasar Variability

    CERN Document Server

    De Vries, W H; White, R L; Loomis, C

    2004-01-01

    In our second paper on long-term quasar variability, we employ a much larger database of quasars than in de Vries, Becker & White. This expanded sample, containing 35165 quasars from the Sloan Digital Sky Survey Data Release 2, and 6413 additional quasars in the same area of the sky taken from the 2dF QSO Redshift Survey, allows us to significantly improve on our earlier conclusions. As before, all the historic quasar photometry has been calibrated onto the SDSS scale by using large numbers of calibration stars around each quasar position. We find the following: (1) the outbursts have an asymmetric light-curve profile, with a fast-rise, slow-decline shape; this argues against a scenario in which micro-lensing events along the line-of-sight to the quasars are dominating the long-term variations in quasars; (2) there is no turnover in the Structure Function of the quasars up to time-scales of ~40 years, and the increase in variability with increasing time-lags is monotonic and constant; and consequently, (3...

  10. Red Galaxy Structures Toward a Large Quasar Group Field

    Science.gov (United States)

    Williger, Gerard M.; Feil, E. C.; Haberzettl, L.; Clowes, R.; Campusano, L.; Haines, C. P.; Valls-Gabaud, D.; Lehnert, M.; Nesvadba, N.; LQG Team

    2014-01-01

    We present data from deep FUV-NUV-griz images toward a 2 sq degree region in the Clowes-Campusano Large Quasar Group field, which contains structures of quasars on the >100 Mpc scale at 0.8 and 1.2. Large Quasar Groups may be the signal posts for galaxy structures analogous to superclusters at high redshift. Using the six band photometry, we calculate photometric redshifts for red-selected galaxies to identify supercluster-size structures, and compare their locations with the quasars in the field.

  11. New X-ray quasars behind the Small Magellanic Cloud

    OpenAIRE

    Dobrzycki, A.; Stanek, K. Z.; Macri, L. M.; Groot, P.J.

    2003-01-01

    We present five X-ray quasars behind the Small Magellanic Cloud, increasing the number of known quasars behind the SMC by ca. 40%. They were identified via follow-up spectroscopy of serendipitous sources from the Chandra X-ray Observatory matched with objects from the OGLE database. All quasars lie behind dense parts of the SMC, and could be very useful for proper motion studies. We analyze X-ray spectral and timing properties of the quasars. We discuss applications of those and other recentl...

  12. An X-ray view of quasars

    CERN Document Server

    Singh, K P

    2013-01-01

    I present an overview of observational studies of quasars of all types, with particular emphasis on X-ray observational studies. The presentation is based on the most popularly accepted unified picture of quasars - collectively referred to as AGN (active galactic nuclei) in this review. Characteristics of X-ray spectra and X-ray variability obtained from various X-ray satellites over the last 5 decades have been presented and discussed. The contribution of AGN in understanding the cosmic X-ray background is discussed very briefly. Attempt has been made to provide up-to-date information; however, this is a vast subject and this presentation is not intended to be comprehensive.

  13. Eigenspectra of the SDSS DR1 quasars

    CERN Document Server

    Yip, C W; Vanden Berk, Daniel E; Ma, Z; Frieman, Joshua A; Subba-Rao, M; Szalay, A S; Yip, Ching-Wa; Connolly, Andrew; Berk, Daniel Vanden; Ma, Zhaoming; Frieman, Joshua; Rao, Mark Subba; Szalay, Alex

    2004-01-01

    We construct eigenspectra from the DR1 quasars in the SDSS using the Karhunen-Lo\\`eve (KL) transform (or Principal Component Analysis, PCA) in different redshift and luminosity bins. We find that the quasar spectra can be classified, by the first two eigenspectra, into a continuous sequence in the variation of the spectral slope. We also find a dependence on redshift and luminosity in the eigencoefficients. The dominant redshift effect is the evolution of the blended Fe~II emission (optical) and the Balmer continuum (the ``small-bump'', $\\lambda_{rest} \\approx 2000-4000$\\AA), while the luminosity effect is related to the Baldwin effect. Correlations among several major broad emission lines are found, including the well-known ``Eigenvector-1''.

  14. The 3000 A bump in quasars

    Science.gov (United States)

    Oke, J. B.; Shields, G. A.; Korycansky, D. G.

    1984-01-01

    New observations of the 3000 A bump in quasars are presented and some simple considerations regarding its physical origin are addressed. Absolute spectrophotometry of 30 quasars with redshifts between 0.53 and 0.70 was obtained with the multichannel spectrometer on the 5 m Hale telescope with a rest wavelength coverage of 2000-5000 A. The continuum observations are well represented by a single power law plus a smooth, broad bump and superposed Fe II multiplets. The strength of the bump correlates fairly well with that of H-beta but poorly with those of the Mg II and Fe II lines. Models consisting of a power law and optically thick hydrogen continua with temperatures of about 12,000 K, and Balmer-edge optical depths equal to three fit the observed energy distributions well. The physical conditions and continuum emission of a dense slab of hydrogen heated by gamma rays are analyzed.

  15. Optical Monitoring of Quasars; 1, Variability

    CERN Document Server

    García, A; Jablonski, F J; Terlevich, R J

    1999-01-01

    We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratorio Nacional de Astrofisica, Brazil, between March 1993 and July 1996. A distinctive feature of this survey is its photometric accuracy, ~ 0.02 V mag, achieved through differential photometry with CCD detectors, what allows the detection of faint levels of variability. We find that the relative variability, delta = sigma / L, observed in the V band is anti-correlated with both luminosity and redshift, although we have no means of discovering the dominant relation, given the strong coupling between luminosity and redshift for the objects in our sample.We introduce a model for the dependence of quasar variability on frequency that is consistent with multi-wavelength observations of the nuclear variability of the Seyfert galaxy NGC 4151. We show that correcting the observed variability for this effect slightly increases the significance of the trends of variability with lumin...

  16. Quasar Accretion Disks Are Strongly Inhomogeneous

    CERN Document Server

    Dexter, Jason

    2010-01-01

    Active galactic nuclei (AGN) have been observed to vary stochastically with 10-20 rms amplitudes over a range of optical wavelengths where the emission arises in an accretion disk. Since the accretion disk is unlikely to vary coherently, local fluctuations may be significantly larger than the global rms variability. We investigate toy models of quasar accretion disks consisting of a number of regions, n, whose temperatures vary independently with an amplitude of \\sigma_T in dex. Models with large fluctuations (\\sigma_T=0.35-0.50) in 100-1000 independently fluctuating zones for every factor of two in radius can explain the observed discrepancy between thin accretion disk sizes inferred from microlensing events and optical luminosity while matching the observed optical variability. For the same range of \\sigma_T, inhomogeneous disk spectra provide excellent fits to the HST quasar composite without invoking global Compton scattering atmospheres to explain the high levels of observed UV emission. Simulated microl...

  17. Mining for Dust in Type 1 Quasars

    Science.gov (United States)

    Krawczyk, Coleman M.; Richards, Gordon T.; Gallagher, S. C.; Leighly, Karen M.; Hewett, Paul C.; Ross, Nicholas P.; Hall, P. B.

    2015-06-01

    We explore the extinction/reddening of ˜35,000 uniformly selected quasars with 0\\lt z≤slant 5.3 in order to better understand their intrinsic optical/ultraviolet (UV) spectral energy distributions. Using rest-frame optical-UV photometry taken from the Sloan Digital Sky Survey’s (SDSS) 7th data release, cross-matched to WISE in the mid-infrared, 2MASS and UKIDSS in the near-infrared, and GALEX in the UV, we isolate outliers in the color distribution and find them well described by an SMC-like reddening law. A hierarchical Bayesian model with a Markov Chain Monte Carlo sampling method was used to find distributions of power law indices and E(B-V) consistent with both the broad absorption line (BAL) and non-BAL samples. We find that, of the ugriz color-selected type 1 quasars in SDSS, 2.5% (13%) of the non-BAL (BAL) sample are consistent with E(B-V)\\gt 0.1 and 0.1% (1.3%) with E(B-V)\\gt 0.2. Simulations show both populations of quasars are intrinsically bluer than the mean composite, with a mean spectral index ({{α }λ }) of -1.79 (-1.83). The emission and absorption-line properties of both samples reveal that quasars with intrinsically red continua have narrower Balmer lines and stronger high-ionization emission lines, the latter indicating a harder continuum in the extreme-UV and the former pointing to differences in black hole mass and/or orientation.

  18. Quasars with Gaia: Identification and Astrophysical Parameters

    OpenAIRE

    Claeskens, Jean-François; Smette, A.; Surdej, Jean

    2005-01-01

    Gaia will provide astrometric and photometric observations for about 500 000 quasars distributed over the whole sky. The latter would constitute an isotropic grid of fixed sources perfectly suited to determine the referential frame. However, they must first be properly identified among stars, whose population is about 2000 times larger. Using broad and medium band photometry, we first compare the efficiency of two analysis methods (Ï 2 fitting and Artificial Neural Networks, ANNs) to produce ...

  19. Quasar Accretion Disks Are Strongly Inhomogeneous

    OpenAIRE

    Dexter, Jason; Agol, Eric

    2010-01-01

    Active galactic nuclei (AGN) have been observed to vary stochastically with 10-20 rms amplitudes over a range of optical wavelengths where the emission arises in an accretion disk. Since the accretion disk is unlikely to vary coherently, local fluctuations may be significantly larger than the global rms variability. We investigate toy models of quasar accretion disks consisting of a number of regions, n, whose temperatures vary independently with an amplitude of \\sigma_T in dex. Models with l...

  20. Modeling quasar accretion disc temperature profiles

    CERN Document Server

    Hall, Patrick B; Chajet, L S; Weiss, E; Nixon, C J

    2013-01-01

    Microlensing observations indicate that quasar accretion discs have half-light radii larger than expected from standard theoretical predictions based on quasar fluxes or black hole masses. Blackburne and colleagues have also found a very weak wavelength dependence of these half-light radii. We consider disc temperature profile models that might match these observations. Nixon and colleagues have suggested that misaligned accretion discs around spinning black holes will be disrupted at radii small enough for the Lense-Thirring torque to overcome the disc's viscous torque. Gas in precessing annuli torn off a disc will spread radially and intersect with the remaining disc, heating the disc at potentially large radii. However, if the intersection occurs at an angle of more than a degree or so, highly supersonic collisions will shock-heat the gas to a Compton temperature of T~10^7 K, and the spectral energy distributions (SEDs) of discs with such shock-heated regions are poor fits to observations of quasar SEDs. T...

  1. Fe II Diagnostic Tools for Quasars

    CERN Document Server

    Verner, E; Verner, D; Johansson, S; Kallman, T; Gull, T R

    2004-01-01

    The enrichment of Fe, relative to alpha-elements such as O and Mg, represents a potential means to determine the age of quasars and probe the galaxy formation epoch. To explore how \\ion{Fe}{2} emission in quasars is linked to physical conditions and abundance, we have constructed a 830-level \\ion{Fe}{2} model atom and investigated through photoionization calculations how \\ion{Fe}{2} emission strengths depend on non-abundance factors. We have split \\ion{Fe}{2} emission into three major wavelength bands, \\ion{Fe}{2} (UV), \\ion{Fe}{2}(Opt1), and \\ion{Fe}{2}(Opt2), and explore how the \\ion{Fe}{2}(UV)/\\ion{Mg}{2}, \\ion{Fe}{2}(UV)/\\ion{Fe}{2}(Opt1) and \\ion{Fe}{2}(UV)/\\ion{Fe}{2}(Opt2) emission ratios depend upon hydrogen density and ionizing flux in broad-line regions (BLR's) of quasars. Our calculations show that: 1) similar \\ion{Fe}{2}(UV)/\\ion{Mg}{2} ratios can exist over a wide range of physical conditions; 2) the \\ion{Fe}{2}(UV)/\\ion{Fe}{2}(Opt1) and \\ion{Fe}{2}(UV)/\\ion{Fe}{2}(Opt2) ratios serve to constrain...

  2. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope Quasar Survey: Quasar Properties from First Data Release

    CERN Document Server

    Ai, Y L; Yang, Jinyi; Yang, Qian; Wang, Feige; Guo, Rui; Zuo, Wenwen; Dong, Xiaoyi; Zhang, Y -X; Yuan, H -L; Song, Y -H; Wang, Jianguo; Dong, Xiaobo; Yang, M; Wu, H; Shen, S -Y; Shi, J -R; He, B -L; Lei, Y -J; Li, Y -B; Luo, A -L; Zhao, Y -H; Zhang, Hao-Tong

    2015-01-01

    We present preliminary results of the quasar survey in Large Sky Area Multi- Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes pilot survey and the first year regular survey. There are 3921 quasars identified with reliability, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with highest z of 4.83. We compile emission line measurements around the H{\\alpha}, H{\\beta}, Mg II, and C IV regions for the new quasars. The continuum luminosities are inferred from SDSS photo- metric data with model fitting as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, and flags indicating the selec- tion methods, broad absorption line quasars. The catalog and spectra for these quasars are available online. 28% of the 3921 quasars are selected with optical- infrared colours independently, indicating that the method is quite promising in completeness of quasar survey. LAMOST DR1 and the on-g...

  3. The Multi-Wavelength Quasar Survey Ⅲ.Quasars in Field 836

    Institute of Scientific and Technical Information of China (English)

    Yu Bai; Yang Chen; Xiang-Tao He; Jiang-Hua Wu; Qing-Kang Li; Richard F.Green; Wolfgang Voges

    2007-01-01

    This is the third Paper in a series connected with our Multiwavelength Quasar Survey.The survey is aimed to provide a quasar sample more complete than any previous survey by using a combined selection technique to reduce selection effects.we present the observational results for the X-ray candidates in field f836.We found 15 X-ray AGNs in this field of which eight are new discoveries.The X-ray data and optical spectra of these AGNs are given.We give the X-ray candidate selection criteria.which proved to be highly efficient in isolating X-ray AGNs.

  4. Seeking the epoch of maximum luminosity for dusty quasars

    International Nuclear Information System (INIS)

    Infrared luminosities νLν(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 quasar Gpc–3 having νLν(7.8 μm) > 1046.6 erg s–1 for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νLν(0.25 μm), have the largest values of the ratio νLν(0.25 μm)/νLν(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  5. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    Science.gov (United States)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature–density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h∼ 2.5× {10}12 {h}-1 {M}ȯ for the lightbulb model, and {M}h∼ 2.3× {10}12 {h}-1 {M}ȯ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5–2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  6. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    Science.gov (United States)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature-density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h˜ 2.5× {10}12 {h}-1 {M}⊙ for the lightbulb model, and {M}h˜ 2.3× {10}12 {h}-1 {M}⊙ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5-2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  7. Teradiode's high brightness semiconductor lasers

    Science.gov (United States)

    Huang, Robin K.; Chann, Bien; Burgess, James; Lochman, Bryan; Zhou, Wang; Cruz, Mike; Cook, Rob; Dugmore, Dan; Shattuck, Jeff; Tayebati, Parviz

    2016-03-01

    TeraDiode is manufacturing multi-kW-class ultra-high brightness fiber-coupled direct diode lasers for industrial applications. A fiber-coupled direct diode laser with a power level of 4,680 W from a 100 μm core diameter, lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 3.5 mm-mrad and is the lowest BPP multi-kW-class direct diode laser yet reported. This laser is suitable for industrial materials processing applications, including sheet metal cutting and welding. This 4-kW fiber-coupled direct diode laser has comparable brightness to that of industrial fiber lasers and CO2 lasers, and is over 10x brighter than state-of-the-art direct diode lasers. We have also demonstrated novel high peak power lasers and high brightness Mid-Infrared Lasers.

  8. Multi-wavelength observations of the gamma-ray flaring quasar S4 1030+61 in 2009-2014

    CERN Document Server

    Kravchenko, E V; Hovatta, T; Ramakrishnan, V

    2016-01-01

    We present a study of the parsec-scale multi-frequency properties of the quasar S4 1030+61 during a prolonged radio and gamma-ray activity. Observations were performed within Fermi gamma-ray telescope, OVRO 40-m telescope and MOJAVE VLBA monitoring programs, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24, and 43 GHz, which were triggered by the bright gamma-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4+-0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and gamma-ray emission implies a spatial separation between emitting regions at these bands of about 12 pc and locates the gamma-ray emission within a parsec from the central engine. We detected changes in the val...

  9. Near-Infrared Spectroscopy of Quasars at z~3 and Estimates of Their Supermassive Black Hole Masses

    CERN Document Server

    Saito, Yuriko; Minowa, Yosuke; Morokuma, Tomoki; Kawaguchi, Toshihiro; Sameshima, Hiroaki; Minezaki, Takeo; Oi, Nagisa; Nagao, Tohru; Kawatatu, Nozomu; Matsuoka, Kenta

    2015-01-01

    We present the results of new infrared spectroscopic observations of 37 quasars at z~3, selected based on the optical r'-band magnitude and the availability of nearby bright stars for future imaging follow-up with Adaptive Optics system. The supermassive black hole (SMBH) masses (M_BH) were successfully estimated in 28 out of 37 observed objects from the combination of the H_beta emission linewidth and continuum luminosity at rest-frame 5100A. Comparing these results with those from previous studies of quasars with similar redshift, our sample exhibited slightly lower (~ -0.11 dex in median) Eddington ratios; and, the SMBH masses are slightly (~ 0.38 dex in median) higher. The SMBH growth time, t_grow, was calculated by dividing the estimated SMBH mass by the mass accretion rate measured using optical luminosity. We found, given reasonable assumptions, that t_grow was smaller than the age of the universe at the redshift of individual quasars for a large fraction of observed sources, suggesting that the SMBHs ...

  10. Serendipitous discovery of an extended X-ray jet without a radio counterpart in a high-redshift quasar

    CERN Document Server

    Simionescu, A; Ichinohe, Y; Cheung, C C; Jamrozy, M; Siemiginowska, A; Hagino, K; Gandhi, P; Werner, N

    2015-01-01

    A recent Chandra observation of the nearby galaxy cluster Abell 585 has led to the discovery of an extended X-ray jet associated with the high-redshift background quasar B3 0727+409, a luminous radio source at redshift z=2.5. This is one of only few examples of high-redshift X-ray jets known to date. It has a clear extension of about 10-12", corresponding to a projected length of 80-100 kpc, with a possible hot spot as far as 35" from the quasar. The archival high resolution VLA maps surprisingly reveal no extended jet emission, except for one knot about 1.4" away from the quasar. The high X-ray to radio luminosity ratio for this source appears consistent with the $\\propto (1+z)^{4}$ amplification expected from the inverse Compton radiative model. This serendipitous discovery may signal the existence of an entire population of similar systems with bright X-ray and faint radio jets at high redshift, a selection bias which must be accounted for when drawing any conclusions about the redshift evolution of jet pr...

  11. Witnessing the key early phase of quasar evolution: an obscured AGN pair in the interacting galaxy IRAS 20210+1121

    CERN Document Server

    Piconcelli, E; Bianchi, S; Mathur, S; Fiore, F; Guainazzi, M; Lanzuisi, G; Maiolino, R; Nicastro, F

    2010-01-01

    We report the discovery of an active galactic nucleus (AGN) pair in the interacting galaxy system IRAS 20210+1121 at z = 0.056. An XMM-Newton observation reveals the presence of an obscured (Nh ~ 5 x 10^{23} cm^-2), Seyfert-like (L_{2-10 keV} = 4.7 x 10^{42} erg/s) nucleus in the northern galaxy, which lacks unambiguous optical AGN signatures. Our spectral analysis also provides strong evidence that the IR-luminous southern galaxy hosts a Type 2 quasar embedded in a bright starburst emission. In particular, the X-ray primary continuum from the nucleus appears totally depressed in the XMM-Newton band as expected in case of a Compton-Thick absorber, and only the emission produced by Compton scattering ('reflection') of the continuum from circumnuclear matter is seen. As such, IRAS 20210+1121 seems to provide an excellent opportunity to witness a key, early phase in the quasar evolution predicted by the theoretical models of quasar activation by galaxy collisions.

  12. Alignment of quasar polarizations with large-scale structures

    Science.gov (United States)

    Hutsemékers, D.; Braibant, L.; Pelgrims, V.; Sluse, D.

    2014-12-01

    We have measured the optical linear polarization of quasars belonging to Gpc scale quasar groups at redshift z ~ 1.3. Out of 93 quasars observed, 19 are significantly polarized. We found that quasar polarization vectors are either parallel or perpendicular to the directions of the large-scale structures to which they belong. Statistical tests indicate that the probability that this effect can be attributed to randomly oriented polarization vectors is on the order of 1%. We also found that quasars with polarization perpendicular to the host structure preferentially have large emission line widths while objects with polarization parallel to the host structure preferentially have small emission line widths. Considering that quasar polarization is usually either parallel or perpendicular to the accretion disk axis depending on the inclination with respect to the line of sight, and that broader emission lines originate from quasars seen at higher inclinations, we conclude that quasar spin axes are likely parallel to their host large-scale structures. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 092.A-0221.Table 1 is available in electronic form at http://www.aanda.org

  13. High resolution VLA observations of quasars with distorted radio structure

    International Nuclear Information System (INIS)

    To examine the physics of distorted quasars, the authors have mapped the quasars 3C 270.1 and 3C 275.1 in both I and P using the VLA A-Array at 20 cm and 6 cm. The results are displayed in tables and figures but are not discussed. (Auth.)

  14. The Sloan Digital Sky Survey quasar catalog: tenth data release

    CERN Document Server

    Pâris, Isabelle; Aubourg, Éric; Ross, Nicholas P; Myers, Adam D; Streblyanska, Alina; Bailey, Stephen; Hall, Patrick B; Strauss, Michael A; Anderson, Scott F; Bizyaev, Dmitry; Borde, Arnaud; Brinkmann, Jon; Bovy, Jo; Brandt, William N; Brewington, Howard; Brownstein, Joel R; Cook, Benjamin A; Ebelke, Garrett; Fan, Xiaohui; Ak, Nurten Filiz; Finley, Hayley; Font-Ribera, Andreu; Ge, Jian; Hamann, Fred; Ho, Shirley; Jiang, Linhua; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Marchante, Moses; McGreer, Ian D; McMahon, Richard G; Miralda-Escudé, Jordi; Muna, Demitri; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pan, Kaike; Perez-Fournon, Ismaël; Pieri, Matthew; Riffel, Rogério; Schlegel, David J; Schneider, Donald P; Simmons, Audrey; Viel, Matteo; Weaver, Benjamin A; Wood-Vasey, W Michael; Yèche, Christophe; York, Donald G

    2013-01-01

    We present the Data Release 10 Quasar (DR10Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the first 2.5 years of the survey and that are confirmed as quasars via visual inspection of the spectra. The catalog also includes known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 166,583 quasars (74,454 are new discoveries since SDSS-DR9) detected over 6,373 deg$^{2}$ with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with $z>2.15$ (117,668) is $\\sim$5 times greater than the number of $z>2.15$ quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII, MgII). The catalog identifies 16,461 broad absorption line quasars and gives their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-...

  15. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

    Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Brandt, W. N.;

    2009-01-01

    We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z > 4. These weak emission-line quasars (WLQs) constitute a prominent...

  16. The EUVE bright source list

    Science.gov (United States)

    Stroozas, B.; Mcdonald, K.; Antia, B.; Mcdonald, J.; Wiercigroch, A.

    1993-01-01

    Initial results for bright extreme ultraviolet sources discovered during the EUVE all-sky and deep ecliptic surveys have been published as a Bright Source List (BSL) and released to the astronomical community with a recent NASA research announcement (NRA 93-OSS-02, Appendix F). This paper describes the data processing software, the EUVE survey data set, and the production of the BSL at the Center for EUV Astrophysics. The contents, format, and selection criteria for sources, the data processing strategy, some problems encountered, and a summary of the BSL results are presented.

  17. All things bright and beautiful

    OpenAIRE

    Brown, Chloe

    2012-01-01

    'All Things Bright and Beautiful' was exhibited in 20/21 Visual Arts Centre, Scunthorpe, which is sited in a 'redundant' church. The fundamental question that the exhibition explored concerned the role of 'the animal' within contemporary art and within secular society, which in turn hoped to prompt reflections on our understanding of the place of 'the human' in the world and in nature. If there is no divine order, as posited by the hymn 'All Things Bright and Beautiful', where does this leave...

  18. Simple Stellar Population Modeling of Low S/N Galaxy Spectra and Quasar Host Galaxy Applications

    CERN Document Server

    Mosby, Gregory; Hooper, Eric; Wolf, Marsha; Sheinis, Andrew; Richards, Joseph

    2014-01-01

    To study the effect of supermassive black holes (SMBHs) on their host galaxies it is important to study the hosts when the SMBH is near its peak activity. A method to investigate the host galaxies of high luminosity quasars is to obtain optical spectra at positions offset from the nucleus where the relative contribution of the quasar and host are comparable. However, at these extended radii the galaxy surface brightness is often low (20-22 mag per arcsec$^{2}$) and the resulting spectrum might have such low S/N that it hinders analysis with standard stellar population modeling techniques. To address this problem we have developed a method that can recover galaxy star formation histories (SFHs) from rest frame optical spectra with S/N $\\sim$ 5~\\AA$^{-1}$. This method uses the statistical technique diffusion k-means to tailor the stellar population modeling basis set. Our diffusion k-means minimal basis set, composed of 4 broad age bins, is successful in recovering a range of galaxy SFHs. Additionally, using an...

  19. Adaptive Optics Imaging of Low-redshift Damped Lyman-alpha Quasar Absorbers

    CERN Document Server

    Chun, M R; Kulkarni, V P; Takamiya, M; Chun, Mark R.; Gharanfoli, Soheila; Kulkarni, Varsha P.; Takamiya, Marianne

    2005-01-01

    We have carried out a high angular resolution near-infrared imaging study of the fields of 6 quasars with 7 strong absorption line systems at z < 0.5, using the Hokupa'a adaptive optics system and the QUIRC near-infrared camera on the Gemini-North telescope. These absorption systems include 4 classical damped Lyman-alpha absorbers (DLAs), 2 sub-DLAs, and one Lyman-limit system. Images were obtained in the H or K' filters with FWHM between 0.2"-0.5" with the goal of detecting the absorbing galaxies and identifying their morphologies. Features are seen at projected separations of 0.5"-16.0" from the quasars and all of the fields show features at less than 2" separation. We find candidate absorbers in all of the seven systems. With the assumption that some of these are associated with the absorbers, the absorbers are low luminosity < 0.1 L*_H or L*_K; we do not find any large bright candidate absorbers in any of our fields. Some fields show compact features that are too faint for quantitative morphology, b...

  20. Searching for the Physical Drivers of Eigenvector-1 From Quasars to Nano-Quasars

    CERN Document Server

    Marziani, P

    2002-01-01

    We point out an analogy between two accreting white dwarfs with jets (CH Cyg and MWC 560) and powerful quasars. In spite of the enormous difference in the mass of the central object (a factor about 10^7), the emission lines are strikingly similar to those of I Zw1 (the prototype "Narrow Line Seyfert 1" nucleus whose spectrum is widely used as an FeII template for almost all quasars). The spectral similarity give us the unique possibility to consider the optical Eigenvector-1 diagram using objects less massive by a factor of millions. Our results reinforce the interpretation of the "Eigenvector-1 correlations" found for low redshift quasars as driven mainly by the source luminosity to central compact object mass ratio(L/M). The accreting white dwarfs CH Cyg and MWC 560, their jets and emission lines, may well represent the low energy, non relativistic end of the accretion phenomena, which encompass the most powerful quasars and the microquasars. The remarkable similarities suggest that they may be legitimately...

  1. Quasar Variability Measurements With SDSS Repeated Imaging and POSS Data

    CERN Document Server

    Ivezic, Z; Juric, M; Anderson, S; Hall, P B; Richards, G T; Rockosi, C M; Vanden Berk, Daniel E; Turner, E L; Knapp, G R; Gunn, J E; Schlegel, D J; Strauss, M A; Schneider, D P

    2004-01-01

    We analyze the properties of quasar variability using repeated SDSS imaging data in five UV-to-far red photometric bands, accurate to 0.02 mag, for 13,000 spectroscopically confirmed quasars. The observed time lags span the range from 3 hours to over 3 years, and constrain the quasar variability for rest-frame time lags of up to two years, and at rest-frame wavelengths from 1000 Ang. to 6000 Ang. We demonstrate that 66,000 SDSS measurements of magnitude differences can be described within the measurement noise by a simple function of only three free parameters. The addition of POSS data constrains the long-term behavior of quasar variability and provides evidence for a turn-over in the structure function. This turn-over indicates that the characteristic time scale for optical variability of quasars is of the order 1 year.

  2. Around the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar II Results for the second observing season

    CERN Document Server

    Colley, W N; Abajas, C; Alcalde, D; Aslan, Z; Bikmaev, I F; Chavushyan, V H; Chinarro, L; Cournoyer, J P; Crowe, R; Dudinov, V; Kathinka, A; Evans, D; Jeon, Y B; Goicoechea, L J; Golbasi, O; Khamitov, I; Kjernsmo, K; Lee, H J; Lee, J; Lee, K W; Lee, M G; López-Cruz, O; Mediavilla, E; Moffatt, A F J; Mujica, R; Ullán, M; Oscoz, A; Park, M G; Purves, N; Sakhibullin, N A; Sinelnikov, I; Stabell, R; Stockton, A; Teuber, J; Thompson, R; Woo, H S; Zheleznyak, A T; Colley, Wesley N.; Schild, Rudolph E.; Abajas, Cristina; Alcalde, David; Aslan, Zeki; Bikmaev, Ilfan; Chavushyan, Vahram; Chinarro, Luis; Cournoyer, Jean-Philippe; Crowe, Richard; Dudinov, Vladimir; Kathinka, Anna; Evans, Dalland; Jeon, Young-Beom; Goicoechea, Luis J.; Golbasi, Orhan; Khamitov, Irek; Kjernsmo, Kjetil; Lee, Hyun Ju; Lee, Jonghwan; Lee, Ki Won; Lee, Myung Gyoon; Lopez-Cruz, Omar; Mediavilla, Evencio; Moffatt, Anthony F.J.; Mujica, Raul; Ullan, Aurora M.; Oscoz, Alexander; Park, Myeong-Gu; Purves, Norman; Sakhibullin, Nail; Sinelnikov, Igor; Stabell, Rolf; Stockton, Alan; Teuber, Jan; Thompson, Roy; Woo, Hwa-Sung

    2003-01-01

    We report on an observing campaign in March 2001 to monitor the brightness of the later arriving Q0957+561 B image in order to compare with the previously published brightness observations of the (first arriving) A image. The 12 participating observatories provided 3543 image frames which we have analyzed for brightness fluctuations. From our classical methods for time delay determination, we find a 417.09 +/- 0.07 day time delay which should be free of effects due to incomplete sampling. During the campaign period, the quasar brightness was relatively constant and only small fluctuations were found; we compare the structure function for the new data with structure function estimates for the 1995--6 epoch, and show that the structure function is statistically non-stationary. We also examine the data for any evidence of correlated fluctuations at zero lag. We discuss the limits to our ability to measure the cosmological time delay if the quasar's emitting surface is time resolved, as seems likely.

  3. Voigt Profile Fitting to Quasar Absorption Lines: A Simple Approximation to the Voigt-Hjerting Function

    CERN Document Server

    García, T T

    2006-01-01

    The Voigt-Hjerting function is fundamental in order to correctly model the profiles of absorption lines imprinted in the spectra of bright background sources (e.g quasars) by intervening neutral hydrogen. In this work we present a simple analytical approximation to this function in the context of intergalactic neutral hydrogen absorption-line profiles. Using basic calculus tools, we derive an expression that contains only fourth order polynomial and Gaussian functions, and that approximates this function with an accuracy better than $10^{-3}$ per cent. In connection with the absorption coefficient of intergalactic neutral hydrogen, $\\tau_{\\mathrm{H I}}(\\lambda)$, this approximation is valid for an arbitrary wavelength baseline, for column densities up to $\

  4. Leveraging Spitzer's Legacy: Quasars and Feedback at High Redshift

    Science.gov (United States)

    Richards, Gordon; Anderson, Scott; Bauer, Franz; Deo, Rajesh; Fan, Xiaohui; Gallagher, Sarah; Myers, Adam; Strauss, Michael; Zakamska, Nadia

    2009-04-01

    Recent research efforts to understand the evolution of galaxies and quasars are beginning to form a consistent picture. Galaxies and their supermassive black holes grow through mergers, but with decreasing characteristic mass scales over time. Much less, however, is known about the evolution of galaxies at high redshifts and the role played by energy injection from the onset of active black hole growth. Understanding these events requires investigating a statistically significant number of high-redshift quasars and crossing the L* boundary in luminosity. To construct an appropriate data set requires both relatively wide-areas (to find these rare objects) and moderate-depth imaging (to probe below L* in luminosity). Unfortunately, existing optical and MIR surveys fail to meet both of these requirements. Furthermore, both optical and MIR quasar selection are blindest at the most crucial redshifts. Here we propose to address these gaps with targeted IRAC observations of a few hundred high-redshift quasars from the Sloan Digital Sky Survey. Such a sample will enable the construction of a proper training set for the discovery of 2.5learn how to identify high-redshift quasars in other fields over a large range in luminosity. With this knowledge, we will crack open the high-z quasar discovery space within existing IRAC legacy surveys (SWIRE, XFLS, Bootes, COSMOS). With a large sample of high-redshift quasars spanning a large range in luminosity, we can turn the quasar luminosity function and quasar clustering analysis into tools for distinguishing between different evolutionary models and feedback prescriptions. In all, we will observe 330 SDSS quasars using 307 pointings/AORs, totaling 48.5 hours of IRAC time.

  5. Dissecting the complex environment of a distant quasar with MUSE

    Science.gov (United States)

    Husband, K.; Bremer, M. N.; Stanway, E. R.; Lehnert, M. D.

    2015-09-01

    High-redshift quasars can be used to trace the early growth of massive galaxies and may be triggered by galaxy-galaxy interactions. We present Multi-Object Spectroscopic Explorer (MUSE) science verification data on one such interacting system consisting of the well-studied z = 3.2 PKS1614+051 quasar, its AGN companion galaxy and bridge of material radiating in Ly α between the quasar and its companion. We find a total of four companion galaxies (at least two galaxies are new discoveries), three of which reside within the likely virial radius of the quasar host, suggesting that the system will evolve into a massive elliptical galaxy by the present day. The MUSE data are of sufficient quality to split the extended Ly α emission line into narrow velocity channels. In these the gas can be seen extending towards each of the three neighbouring galaxies suggesting that the emission-line gas originates in a gravitational interaction between the galaxies and the quasar host. The photoionization source of this gas is less clear but is probably dominated by the two AGN. The quasar's Ly α emission spectrum is double peaked, likely due to absorbing neutral material at the quasar's systemic redshift with a low column density as no damping wings are present. The spectral profiles of the AGN and bridge's Ly α emission are also consistent with absorption at the same redshift indicating that this neutral material may extend over >50 kpc. The fact that the neutral material is seen in the line of sight to the quasar and transverse to it, and the fact that we see the quasar and it also illuminates the emission-line bridge, suggests that the quasar radiates isotropically and any obscuring torus is small. These results demonstrate the power of MUSE for investigating the dynamics of interacting systems at high redshift.

  6. Quasars Probing Quasars VIII. The Physical Properties of the Cool Circumgalactic medium Surrounding z ~ 2-3 Massive Galaxies

    CERN Document Server

    Lau, Marie Wingyee; Hennawi, Joseph F

    2015-01-01

    We characterize the physical properties of the cool T ~ 10^4 K circumgalactic medium surrounding z ~ 2-3 quasar host galaxies, which are predicted to evolve into present day massive ellipticals. Using a statistical sample of 14 quasar pairs with projected separation 100 cm^-3 and subparsec scale gas clumps.

  7. An Ultra-luminous Quasar at z = 5.363 with a Ten Billion Solar Mass Black Hole and a Metal-rich DLA at z ∼ 5

    Science.gov (United States)

    Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; Yang, Jinyi; Cai, Zheng; Yi, Weimin; Zuo, Wenwen; Wang, Ran; McGreer, Ian D.; Ho, Luis C.; Kim, Minjin; Yang, Qian; Bian, Fuyan; Jiang, Linhua

    2015-07-01

    We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a supermassive black hole with {M}{BH}=(1.07+/- 0.27)× {10}10 {M}ȯ . With an absolute magnitude {M}1450=-28.92 and a bolometric luminosity {L}{bol}∼ 3.4× {10}14{L}ȯ , J0306+1853 is one of the most luminous objects in the early universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness, and normal broad emission lines. In addition, a z=4.986 damped Lyα system (DLA) with [{{M}}/{{H}}]=-1.3+/- 0.1, among the most metal-rich DLAs at z≳ 5, is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraints on the bright end of the quasar luminosity function and massive end of the black hole mass function. It will provide a unique laboratory for the study of BH growth and the co-evolution between a BH and the host galaxy with multi-wavelength follow-up observations. The future high-resolution spectra will give more insight into the DLA and other absorption systems along the line of sight of J0306+1853.

  8. The z=0.0912 and z=0.2212 Damped Lyman Alpha Galaxies Along the Sight-Line Toward the Quasar OI 363

    CERN Document Server

    Turnshek, D A; Nestor, D; Lane, W; Monier, E M; Bergeron, J; Smette, A

    2000-01-01

    New optical and infrared observations along the sight-line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding systems which lack confirming UV spectroscopic observations of the actual Lyman alpha line, this sight-line presently contains the two lowest-redshift classical damped Lyman alpha (DLA) quasar absorption line systems known (i.e. with N(HI) \\ge 2 x 10^{20} atoms cm^{-2}), one at z(abs)=0.0912 and the other at z(abs)=0.2212. The z=0.09 DLA galaxy appears to be an extended low surface brightness galaxy which is easily visible only in infrared images and shows rich morphological structure. Subtraction of the quasar nuclear and host light yields L_K \\approx 0.08L_K* at z=0.09. The impact parameter between the galaxy and quasar sight-line is very small, b<3.6 kpc (<2 arcsec), which makes measurements difficult. The z=0.22 DLA galaxy is an early-type dwarf with a K-band luminosity of L_K \\approx 0.1L_K* at impact parameter b=20 kpc. In general, these results serve to support mou...

  9. Bright Transients discovered by PSST

    Science.gov (United States)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Young, D. R.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-08-01

    Six bright transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  10. The VLBI structure of radio-loud Broad Absorption Line quasars

    Science.gov (United States)

    Liu, Y.; Jiang, D. R.; Gu, M.

    2016-02-01

    The nature and origin of Broad Absorption Line (BAL) quasars and their relationship to non-BAL quasars are an open question. The BAL quasars are probably normal quasars seen along a particular line of sight. Alternatively, they are young or recently refueled. The high resolution radio morphology of BAL quasars is very important to understand the radio properties of BAL quasars. We present VLBA observations at L and C bands for a sample of BAL quasars. The observations will help us to explore the VLBI radio properties, and distinguish the present models of explaining BAL phenomena.

  11. Nuclear structure of quasars at 329 megahertz

    International Nuclear Information System (INIS)

    This thesis presents studies of compact quasars using Very Long Baseline Interferometry at 329 MHz. Chapter 1 presents hybrid maps of 3C147 and 3C286, made at 329 MHz from VLBI observations taken in 1975 with three stations. These are the first maps of compact radio structure at this frequency. Both objects have an unresolved core; an extended, asymmetric jet; and an even larger, completely resolved halo. For 3C147 it is possible to decompose the spectrum into individual component spectra; at 329 MHz the core of 3C147 is self-absorbed. For both sources the spectral index decreases monotonically from core to jet to halo. Chapter 2 presents further 329 MHz VLBI observations. Seven stations were used to map the quasars 3C48, 3C147, 3C309.1, 3C380, and 3C454.3. These are the first reliable, high dynamic range maps at this frequency, and reveal complex structure in four of these sources. All five quasars are seen to have asymmetric structure that can be interpreted in the ''core-jet'' picture of compact extragalactic radio sources. Chapter 3 analyzes the two maps of 3C147 presented in chapters 1 and 2. Those maps reveal that the core of 3C147 is a low-frequency variable radio source which has brightened by a factor of two in six years. In combination with X-ray observations, this is used to demonstrate that bulk relativistic motion is taking place within the core, and leads the prediction that 3C147 is a ''superluminal'' radio source. In chapter 4, the observations presented in chapter 2 are analyzed using standard synchrotron theory to discover conditions occurring in these objects

  12. The high-z quasar Hubble Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Melia, Fulvio, E-mail: fmelia@email.arizona.edu [Department of Physics, the Applied Math Program, and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (United States)

    2014-01-01

    Two recent discoveries have made it possible for us to begin using high-z quasars as standard candles to construct a Hubble Diagram (HD) at z > 6. These are (1) the recognition from reverberation mapping that a relationship exists between the optical/UV luminosity and the distance of line-emitting gas from the central ionizing source. Thus, together with a measurement of the velocity of the line-emitting gas, e.g., via the width of BLR lines, such as Mg II, a single observation can therefore in principle provide a determination of the black hole's mass; and (2) the identification of quasar ULAS J1120+0641 at z = 7.085, which has significantly extended the redshift range of these sources, providing essential leverage when fitting theoretical luminosity distances to the data. In this paper, we use the observed fluxes and Mg II line-widths of these sources to show that one may reasonably test the predicted high-z distance versus redshift relationship, and we assemble a sample of 20 currently available high-z quasars for this exercise. We find a good match between theory and observations, suggesting that a more complete, high-quality survey may indeed eventually produce an HD to complement the highly-detailed study already underway (e.g., with Type Ia SNe, GRBs, and cosmic chronometers) at lower redshifts. With the modest sample we have here, we show that the R{sub h} = ct Universe and ΛCDM both fit the data quite well, though the smaller number of free parameters in the former produces a more favorable outcome when we calculate likelihoods using the Akaike, Kullback, and Bayes Information Criteria. These three statistical tools result in similar probabilities, indicating that the R{sub h} = ct Universe is more likely than ΛCDM to be correct, by a ratio of about 85% to 15%.

  13. Quasar Outflows and Black Hole Masses

    Science.gov (United States)

    Coatman, Liam; Hewett, Paul; Banerji, Manda; Richards, Gordon; Hennawi, Joseph; Prochaska, Jason X.

    2016-08-01

    Black-hole masses are crucial to understanding the physics of the connection between quasars and their host galaxies and measuring cosmic black hole-growth. At high redshift, z > 2, black hole masses are normally derived using the velocity-width of the CIV broad emission line, based on the assumption that the observed velocity-widths arise from virial-induced motions. In many quasars, the CIV-emission line exhibits significant blue asymmetries ('blueshifts') with the line centroid displaced by up to thousands of km/s to the blue. These blueshifts almost certainly signal the presence of strong outflows, most likely originating in a disc wind. Using both archival data and new observations, we have obtained near-infrared spectra, including the Ha and/or Hb emission lines, for ~400 luminous (L_Bol = 45.5-48.5 erg/s) SDSS quasars, at redshifts 1.5 population. A strong correlation between CIV-velocity width and blueshift is found and, at large blueshifts, >2000 km/s, the velocity-widths appear to be dominated by non-virial motions. Using the Ha/Hb emission to provide black hole masses free from non-virial contributions, we are able to derive a quantitative correction to the CIV-based black-hole masses as a function of blueshift. This correction reduces the scatter between Ha/Hb and CIV velocity widths to just ~0.1 dex. Without the correction, black hole masses would be overestimated by a factor of nine at the largest blueshifts. With a suitable systemic redshift-estimation algorithm, this correction can be straightforwardly applied based only on information contained in the rest-frame UV spectra.

  14. Parsec-scale radio structures in Quasars

    Science.gov (United States)

    Coldwell, G.; Paragi, Z.; Gurvits, L.

    Very Long Baseline Interferometry (VLBI) con su nueva extensión para el radio telescopio orbital, VSOP/HALCA, ofrece una incomparable resolución angular alcanzando escalas de milisegundos y submilisegundos de arco a longitudes de onda de centímetros. En este trabajo presentamos observaciones y análisis de estructuras en radio, en escalas de parsec, para 3 radio fuentes extragalácticas de la muestra de VSOP Survey y 1 quasar, 1442+101, del proyecto `VSOP High Redshift'.

  15. Neutrinos from flat-spectrum radio quasars

    Science.gov (United States)

    Mannheim, K.; Stanev, T.; Biermann, P. L.

    1992-01-01

    The GRO observation (Hartman et al., 1992) of a very strong flux of gamma rays with an energy index close to 2 from the distant quasar 3C279 and other extragalactic flat-spectrum radio sources is in very good agreement with models that advocate the important role of very high energy protons and nuclei in the energy transport in AGN. Protons and nuclei cool by interactions on the nonthermal fields in the nuclear jet of the AGN and generate gamma ray and neutrino fluxes. Ultra high energy neutrinos could be observed with sensitive air shower experiments in outbursts as powerful as the one seen by GRO.

  16. Wavelet analysis of 'double quasar' flux data

    Science.gov (United States)

    Hjorth, P. G.; Villemoes, L. F.; Teuber, J.; Florentin-Nielsen, R.

    1992-02-01

    We have used a wavelet transform method to extract time delay information from the light curves of the gravitationally lensed quasar 0957+561 A,B. The time-frequency performance of wavelet transforms is different from that of, e.g., windowed Fourier transforms in allowing a better temporal resolution and localization of the multiple scales of the signal. It is shown that the discrepancies between the time delays derived by different authors may in part be ascribed to the choice of reduction method.

  17. A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255 II. Emission- and absorption-line variability time lags

    CERN Document Server

    Saturni, F G; Vagnetti, F; Perna, M; Dadina, M

    2015-01-01

    The study of high-redshift bright quasars is crucial to gather information about the history of galaxy assembly and evolution. Variability analyses can provide useful data on the physics of the quasar processes and their relation with the host galaxy. In this study, we aim at measuring the black hole mass of the bright lensed BAL QSO APM 08279+5255 at $z=3.911$ through reverberation mapping, and at updating and extending the monitoring of its C IV absorption line variability. Thanks to 138 R-band photometric data and 30 spectra available over 16 years of observations, we perform the first reverberation mapping of the Si IV and C IV emission lines for a high-luminosity quasar at high redshift. We also cross-correlate the C IV absorption equivalent width variations with the continuum light curve, in order to estimate the recombination time lags of the various absorbers and infer the physical conditions of the ionised gas. We find a reverberation-mapping time lag of $\\sim 900$ rest-frame days for both Si IV and ...

  18. Unveiling the Intrinsic X-ray Properties of Broad Absorption Line Quasars with a Relatively Unbiased Sample

    CERN Document Server

    Morabito, Leah K; Leighly, Karen M; Sivakoff, Gregory R; Shankar, Francesco

    2013-01-01

    There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at $z\\sim2$, selected from a near-infrared (2MASS) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically-faint ($i-K_s\\geq 2.3$ mag) and optically-bright ($i-K_s < 2.3$ mag) samples to be $\\Gamma \\simeq 1.5$--2.1. We constrain their intrinsic column density by modelling the X-ray fractional hardness ratio, finding a mean column density of $3.5\\times10^{22}$ \\cmsq\\ assuming neutral absorption. We incorporate SDSS optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We find that the optically-faint BALQSOs are X-ray weaker than the optically-bright ones, and ...

  19. A reduced orbital period for the supermassive black hole binary candidate in the quasar PG 1302-102?

    CERN Document Server

    D'Orazio, Daniel J; Duffell, Paul; Farris, Brian D; MacFadyen, Andrew I

    2015-01-01

    Graham et al. (2015) have detected a 5.2 year periodic optical variability of the quasar PG 1302-102 at redshift $z=0.3$, which they interpret as the redshifted orbital period $(1+z)t_{\\rm bin}$ of a putative supermassive black hole binary (SMBHB). Here we consider the implications of a $3-8$ times shorter orbital period, suggested by hydrodynamical simulations of circumbinary discs (CBDs) with nearly equal--mass SMBHBs ($q\\equiv M_2/M_1\\gtrsim 0.3$). With the corresponding $2-4$ times tighter binary separation, PG 1302 would be undergoing gravitational wave dominated inspiral, and serve as a proof that the BHs can be fueled and produce bright emission even in this late stage of the merger. The expected fraction of binaries with the shorter $t_{\\rm bin}$, among bright quasars, would be reduced by 1-2 orders of magnitude, compared to the 5.2 year period, in better agreement with the rarity of candidates reported by Graham et al. (2015). Finally, shorter periods would imply higher binary speeds, possibly imprin...

  20. Extreme Brightness Temperatures and Refractive Substructure in 3C273 with RadioAstron

    CERN Document Server

    Johnson, Michael D; Gwinn, Carl R; Gurvits, Leonid I; Narayan, Ramesh; Macquart, Jean-Pierre; Jauncey, David L; Voitsik, Peter A; Anderson, James M; Sokolovsky, Kirill V; Lisakov, Mikhail M

    2016-01-01

    Earth-space interferometry with RadioAstron provides the highest direct angular resolution ever achieved in astronomy at any wavelength. RadioAstron detections of the classic quasar 3C273 on interferometric baselines up to 171,000 km suggest brightness temperatures exceeding expected limits from the "inverse-Compton catastrophe" by two orders of magnitude. We show that at 18 cm, these estimates most probably arise from refractive substructure introduced by scattering in the interstellar medium. We use the scattering properties to estimate an intrinsic brightness temperature of 7*10^12 K, which is consistent with expected theoretical limits, but which is ~15 times lower than estimates that neglect substructure. At 6 cm, the substructure influences the measured values appreciably but gives an estimated brightness temperature that is comparable to models that do not account for the substructure. At 1.3 cm, the substructure does not affect the extremely high inferred brightness temperatures, in excess of 10^13 K....

  1. The soft x-ray properties of a complete sample of optically selected quasars. 1: First results

    Science.gov (United States)

    Laor, Ari; Fiore, Fabrizio; Elvis, Martin; Wilkes, Belinda J.; Mcdowell, Jonathan C.

    1994-01-01

    We present the results of ROSAT position sensitive proportional counter (PSPC) observations of 10 quasars. These objects are part of our ROSAT program to observe a complete sample of optically selected quasars. This sample includes all 23 quasars from the bright quasar survey with a redshift z less than or = 0.400 and a Galactic H I column density N(sup Gal sub H I) less than 1.9 x 10(exp 20)/sq cm. These selection criteria, combined with the high sensitivity and improved energy resolution of the PSPC, allow us to determine the soft (approximately 0.2-2 keV) X-ray spectra of quasars with about an order of magnitude higher precision compared with earlier soft X-ray observations. The following main results are obtained: Strong correlations are suggested between the soft X-ray spectral slope alpha(sub x) and the following emission line parameters: H beta Full Width at Half Maximum (FWHM), L(sub O III), and the Fe II/H beta flux ratio. These correlations imply the following: (1) The quasar's environment is likely to be optically thin down to approximately 0.2 keV. (2) In most objects alpha(sub x) varies by less than approximately 10% on timescales shorter than a few years. (3) alpha(sub x) might be a useful absolute luminosity indicator in quasars. (4) The Galactic He I and H I column densities are well correlated. Most spectra are well characterized by a simple power law, with no evidence for either significant absorption excess or emission excess at low energies, to within approximately 30%. We find mean value of alpha(sub x) = -1.50 +/- 0.40, which is consistent with other ROSAT observations of quasars. However, this average is significantly steeper than suggested by earlier soft X-ray observations of the Einstein IPC. The 0.3 keV flux in our sample can be predicted to better than a factor of 2 once the 1.69 micrometer(s) flux is given. This implies that the X-ray variability power spectra of quasars flattens out between f approximately 10(exp -5) and f

  2. Quasar feedback at the peak of the galaxy formation epoch

    Science.gov (United States)

    Alexandroff, Rachael; Zakamska, Nadia; Liu, Guilin; Greene, Jenny; Strauss, Michael

    2014-08-01

    Feedback from accreting supermassive black holes is now a standard ingredient in galaxy formation models. It is seen as necessary for limiting the maximal masses of galaxies and for establishing the black- hole / bulge correlations. Using Gemini GMOS, we demonstrated that powerful ionized gas winds are a ubiquitous feature in luminous obscured z=0.5 quasars. We now propose to extend this discovery to the epoch of peak galaxy formation and quasar activity - to the era at which feedback was most prominent and the galaxy / black hole correlations were established. We request 4.5 hours of Gemini-NIFS LGS adaptive- optics observations of an extremely luminous moderately obscured quasar at z=2.3 to map the morphology and kinematics of the ionized gas and to determine whether it exhibits the signs of black hole feedback in the form of an unbound ionized gas outflow. We will observe H(beta) and [OIII](lambda)5007Ain the H-band and H(alpha) and [NII](lambda)(lambda)6548,6583Ain the K-band on sub-galactic and galaxy-wide scales (spatial resolution 0.8 kpc, field of view 24 kpc). Obscured quasars likely constitute the majority of the quasar population and may represent the relatively early enshrouded phase of the black hole growth; thus, luminous obscured quasars are the most likely sites of quasar feedback, in agreement with our findings at low redshift.

  3. Similarity of ionized gas nebulae around unobscured and obscured quasars

    CERN Document Server

    Liu, Guilin; Greene, Jenny E

    2014-01-01

    Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III]5007 emission line. We find that ionized gas nebulae extend out to ~13 kpc from the quasar, that they are smooth and round, and that their kinematics are inconsistent with gas in dynamical equilibrium with the host galaxy. The observed morphological and kinematic properties are strikingly similar to those of ionized gas around obscured (type 2) quasars with matched [O III] luminosity, with marginal evidence that nebulae around unobscured quasars are slightly more compact. Therefore in samples of obscured and unob...

  4. Quasar Clustering from SDSS DR5: Dependences on Physical Properties

    CERN Document Server

    Shen, Yue; Ross, Nicholas P; Hall, Patrick B; Lin, Yen-Ting; Richards, Gordon T; Schneider, Donald P; Weinberg, David H; Connolly, Andrew J; Fan, Xiaohui; Hennawi, Joseph F; Shankar, Francesco; Berk, Daniel E Vanden; Bahcall, Neta A; Brunner, Robert J

    2008-01-01

    Using a homogenous sample of 38,208 quasars with a sky coverage of $4000 {\\rm deg^2}$ drawn from the SDSS Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole mass, quasar color, and radio loudness. At $z<2.5$, quasar clustering depends weakly on luminosity and virial black hole mass, with typical uncertainty levels $\\sim 10%$ for the measured correlation lengths. These weak dependences are consistent with models in which substantial scatter between quasar luminosity, virial black hole mass and the host dark matter halo mass has diluted any clustering difference, where halo mass is assumed to be the relevant quantity that best correlates with clustering strength. However, the most luminous and most massive quasars are more strongly clustered (at the $\\sim 2\\sigma$ level) than the remainder of the sample, which we attribute to the rapid increase of the bias factor at the high-mass end of host halos. We do not observe a strong dependence of clusterin...

  5. Distributions of Quasar Hosts on the Galaxy Main Sequence Plane

    Science.gov (United States)

    Zhang, Zhoujian; Shi, Yong; Rieke, George H.; Xia, Xiaoyang; Wang, Yikang; Sun, Bingqing; Wan, Linfeng

    2016-03-01

    The relation between star formation rates (SFRs) and stellar masses, i.e., the galaxy main sequence, is a useful diagnostic of galaxy evolution. We present the distributions relative to the main sequence of 55 optically selected PG and 12 near-IR-selected Two Micron All Sky Survey (2MASS) quasars at z ≤ 0.5. We estimate the quasar host stellar masses from Hubble Space Telescope or ground-based AO photometry, and the SFRs through the mid-infrared aromatic features and far-IR photometry. We find that PG quasar hosts more or less follow the main sequence defined by normal star-forming galaxies while 2MASS quasar hosts lie systematically above the main sequence. PG and 2MASS quasars with higher nuclear luminosities seem to have higher specific SFRs (sSFRs), although there is a large scatter. No trends are seen between sSFRs and SMBH masses, Eddington ratios, or even morphology types (ellipticals, spirals, and mergers). Our results could be placed in an evolutionary scenario with quasars emerging during the transition from ULIRGs/mergers to ellipticals. However, combined with results at higher redshift, they suggest that quasars can be widely triggered in normal galaxies as long as they contain abundant gas and have ongoing star formation.

  6. Quasar Accretion Disks are Strongly Inhomogeneous

    Science.gov (United States)

    Dexter, Jason; Agol, Eric

    2011-01-01

    Active galactic nuclei have been observed to vary stochastically with 10%-20% rms amplitudes over a range of optical wavelengths where the emission arises in an accretion disk. Since the accretion disk is unlikely to vary coherently, local fluctuations may be significantly larger than the global rms variability. We investigate toy models of quasar accretion disks consisting of a number of regions, n, whose temperatures vary independently with an amplitude of σ T in dex. Models with large fluctuations (σ T = 0.35-0.50) in 102-103 independently fluctuating zones for every factor of two in radius can explain the observed discrepancy between thin accretion disk sizes inferred from microlensing events and optical luminosity while matching the observed optical variability. For the same range of σ T , inhomogeneous disk spectra provide excellent fits to the Hubble Space Telescope quasar composite without invoking global Compton scattering atmospheres to explain the high levels of observed UV emission. Simulated microlensing light curves for the Einstein cross from our time-varying toy models are well fit using a time-steady power-law temperature disk and produce magnification light curves that are consistent with current microlensing observations. Deviations due to the inhomogeneous, time-dependent disk structure should occur above the 1% level in the light curves, detectable in future microlensing observations with millimagnitude sensitivity.

  7. Helmholtz bright and boundary solitons

    Energy Technology Data Exchange (ETDEWEB)

    Christian, J M [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); McDonald, G S [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); Chamorro-Posada, P [Departmento de TeorIa de la Senal y Comunicaciones e IngenierIa Telematica, Universidad de Valladolid, ETSI Telecomunicacion, Campus Miguel Delibes s/n, 47011 Valladolid (Spain)

    2007-02-16

    We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts.

  8. GPM Intercalibrated Radiometer Brightness Temperatures

    Science.gov (United States)

    Stocker, Erich Franz; Chou, Joyce

    2013-04-01

    One of the keys to consistent precipitation retrieval from passive microwave radiometer measurements (whether imagers or sounders) is accurate, long-term consistent brightness temperature retrievals. This becomes doubly important when there measurements are taken from radiometers on multiple platforms, from multiple agencies, with many different purposes. The Global Precipitation Measurement (GPM) mission addresses this issue directly with the production of intercalibrated brightness temperatures from all the partner satellites contributing to the GPM mission. These intercalibrated brightness temperatures are given the product designation: 1C within GPM. This paper will describe the GPM approach to intercalibration 1C products. The intercalibration and creation of the products uses a 5-step methodology: comparison of the partner standard products (either Tb or Ta) with the GPM reference standard; determination of adjustments that should be made to each product to create consistent brightness temperatures; re-orbitization of all orbits (in non-realtime) to be in the standard GPM south-south orbit; application of the adjustments to the partner provide 1B(or 1A) products; production of 1C products in HDF5 using a "standard" logical format for any radiometer regardless of its 1B format. This paper describes each of these steps and provides the background for them. It discusses in some detail the current 1C logical format and why this format facilitates use by downstream product algorithms and end-users. Most importantly it provides the analysis approach established by the GPM inter-calibration working group in establishing the adjustments to be made at the 1C level. Finally, using DMSP F16-18, it provides examples of the 1C products and discusses the adjustments that are made.

  9. Bright solitons from defocusing nonlinearities

    OpenAIRE

    Borovkova, Olga V.; Kartashov, Yaroslav; Torner Sabata, Lluís; Malomed, Boris A.

    2011-01-01

    We report that defocusing cubic media with spatially inhomogeneous nonlinearity, whose strength increases rapidly enough toward the periphery, can support stable bright localized modes. Such nonlinearity landscapes give rise to a variety of stable solitons in all three dimensions, including one-dimensional fundamental and multihump states, two-dimensional vortex solitons with arbitrarily high topological charges, and fundamental solitons in three dimensions. Solitons maintain their coherence ...

  10. Relations between the emission spectra and radio structures of quasars

    International Nuclear Information System (INIS)

    We present evidence that the emission spectra and radio structures of low-redshift quasars are related statistically. Our sample compriese 34 quasars with z<0.70 and known radio structures. Objects with the broadest and most irregular emission lines are associated with extended radio sources, while those with relatively narrow emission lines with smooth profiles tend to have compact radio structures. There is also a significant tendency for Fe II emission lines to be found preferentially in quasars with compact radio structure

  11. How do optically-similar quasars look elsewhere?

    Science.gov (United States)

    Shang, Zhaohui; Ma, Bin; Brotherton, Michael S.

    2016-06-01

    As too many spectroscopic and physical parameters complicates the study of quasars, reducing the number of parameters can help to isolate many problems in general. Using spectral principal component analysis, we selected from SDSS a pilot sample of quasars with virtually identical spectral features in H-beta region. We found that they also show very similar spectral features outside the H-beta region in the optical band. We also explore their properties in other available wavelength bands and plan to study the accretion, ionization, and possibly geometry of quasars using this controlled sample.

  12. A survey of z > 5.7 quasars in the sloan digital sky survey. 4. discovery of seven additional quasars

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiao-Hui; Strauss, Michael A.; Richards, Gordon T.; Hennawi, Joseph F.; Becker, Robert H.; White, Richard L.; Diamond-Stanic, Aleksandar M.; onley, Jennifer L.D; Jiang, Lin-Hua; Kim, J.Serena; Vestergaard, Marianne; Young, Jason E.; Gunn, James E.; Lupton, Robert H.; Knapp, Gillian R.; Schneider, Donald P.; Brandt, W.N.; Bahcall, Neta A.; Barentine, J.C.; Brinkmann, J.; Brewington, Howard J.; /Arizona U., Astron. Dept. - Steward Observ. /Princeton U. Observ. /Johns Hopkins U. /UC, Berkeley, Astron. Dept. /UC, Davis

    2005-12-01

    We present the discovery of seven quasars at z > 5.7, selected from {approx}2000 deg{sup 2} of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger photometric errors and are not part of the complete sample. One of the new quasars, SDSS J1335+3533 (z = 5.93), exhibits no emission lines; the 3-{sigma} limit on the rest-frame equivalent width of Ly{alpha} + NV line is 5 {angstrom}. It is the highest redshift lineless quasar known, and could be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z > 6 quasars, SDSS 1250+3130 (z = 6.13) and SDSS J1137+3549 (z = 6.01), show deep Gunn-Peterson absorption gaps in Ly{alpha}. These gaps are narrower the complete Gunn-Peterson absorption troughs observed among quasars at z > 6.2 and do not have complete Ly{beta} absorption.

  13. High brightness semiconductor lasers with reduced filamentation

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter.; Skovgaard, Peter M. W.;

    1999-01-01

    High brightness semiconductor lasers have applications in spectroscopy, fiber lasers, manufacturing and materials processing, medicine and free space communication or energy transfer. The main difficulty associated with high brightness is that, because of COD, high power requires a large aperture...

  14. Post-Starburst Quasars: Bridging the Gap Between Post-Starburst Galaxies and Quasars

    CERN Document Server

    Cales, Sabrina L

    2015-01-01

    In order to better understand the nature of post-starburst quasars (PSQs) in the context of galaxy evolution, we compare their properties to those of post-starburst galaxies and quasars from appropriately selected samples possessing similar redshift ($z \\sim 0.3$), luminosity ($M_r \\sim -$23), and data quality. We consider morphologies, spectral features, and derived physical properties of the stellar populations and central supermassive black hole. PSQs themselves come in two types: the more luminous AGNs with more luminous post-starburst stellar populations hosted by elliptical galaxies, some which are clearly merger products, and the less luminous systems existing within relatively undisturbed spiral galaxies and possessing signs of a more extended period of star formation. Post-starburst galaxies (PSQs) have elliptical and disturbed/post-merger morphologies similar to those of the more luminous PSQs, display similar spectral properties, but also can have younger stellar populations for a given starburst m...

  15. High-brightness rf linear accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Jameson, R.A.

    1986-01-01

    The issue of high brightness and its ramifications in linacs driven by radio-frequency fields is discussed. A history of the RF linacs is reviewed briefly. Some current applications are then examined that are driving progress in RF linacs. The physics affecting the brightness of RF linacs is then discussed, followed by the economic feasibility of higher brightness machines. (LEW)

  16. THE MAGELLANIC QUASARS SURVEY. II. CONFIRMATION OF 144 NEW ACTIVE GALACTIC NUCLEI BEHIND THE SOUTHERN EDGE OF THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    We quadruple the number of quasars known behind the Large Magellanic Cloud (LMC) from 56 (42 in the Optical Gravitational Lensing Experiment (OGLE)-III LMC fields) to 200 by spectroscopically confirming 169 (144 new) quasars from a sample of 845 observed candidates in four ∼3 deg2 Anglo-Australian Telescope/AAOmega fields south of the LMC center. The candidates were selected based on their Spitzer mid-infrared colors, X-ray emission, and/or optical variability properties in the database of the OGLE microlensing survey. The contaminating sources can be divided into 115 young stellar objects (YSOs), 17 planetary nebulae (PNe), 39 Be and 24 blue stars, 68 red stars, and 12 objects classed as either YSO/PN or blue star/YSO. There are also 402 targets with either featureless spectra or too low signal-to-noise ratios for source classification. Our quasar sample is 50% (30%) complete at I = 18.6 mag (19.3 mag). The newly discovered active galactic nuclei (AGNs) provide many additional reference points for proper motion studies of the LMC, and the sample includes 10 bright AGNs (I < 18 mag) that are potentially suitable for absorption line studies. Their primary use, however, is for detailed studies of quasar variability, as they all have long-term, high cadence, continuously growing light curves from the microlensing surveys of the LMC. Completing the existing Magellanic Quasars Survey fields in the LMC and Small Magellanic Cloud should yield a sample of ∼700 well-monitored AGNs, and expanding it to the larger regions covered by the OGLE-IV survey should yield a sample of ∼3600 AGNs.

  17. Cosmology with AGN: can we use quasars as standard candles?

    Science.gov (United States)

    Risaliti, G.

    2016-06-01

    The non-linear relation between X-ray and UV luminosity in quasars can be used to estimate their distance. Recently, we have shown that despite the large dispersion of the relation, a Hubble Diagram made of large samples of quasars can provide unique constraints on cosmology at high redshift. Furthermore, the dispersion of the relation is heavily affected by measurement errors: until now we have used serendipitous X-ray observations, but dedicated observations would significantly increase the precision of the distance estimates. I discuss the future role of XMM in this new field, showing (1) the fundamental contribution of the Serendipitous Source Catalogue and of large surveys, and (2) the breakthrough advancements we may achieve with the observation of a large number of SDSS quasars at high redshift: every 12-15 quasars observed at z~3 would be equivalent to discovering a supernova at that redshift.

  18. New sample of quasars to B = 22. 0

    Energy Technology Data Exchange (ETDEWEB)

    Marano, B.; Zamorani, G.; Zitelli, V.

    1988-05-01

    Data for a new sample of optically selected quasars are presented. The 'standard' multicolour technique for selecting quasar candidates has been applied to all the objects brighter than J = 22.0 in a field of 0.69 deg/sup 2/. Additional candidates have been selected from a search on grism plates obtained in the same area and through a variability analysis on two sets of plates taken one year apart from each other. Slit spectroscopy for all the high priority candidates brighter than J 20.9 has provided a sample of 23 confirmed quasars. Within this magnitude limit colour and grism selections have been about equally successful in selecting quasars.

  19. Distribution of Doppler Redshifts of Associated Absorbers of SDSS Quasars

    Indian Academy of Sciences (India)

    Cai-Juan Pan; Zhi-Fu Chen

    2013-12-01

    Doppler redshifts of a sample of Mg II associated absorbers of SDSS DR7 quasars are analysed. We find that there might be three Gaussian components in the distribution of the Doppler redshift. The first Gaussian component, with the peak being located at Dopp = -0.0074, probably arises from absorbers with outflow histories observed in the direction close to jets of quasars. The second Gaussian component, with the peak being located at Dopp = -0.0017, possibly arises from absorbers with outflow histories observed in the direction far away from jets of quasars. Whereas, the third Gaussian component, with the peak being located at Dopp = -0.0004, might arise from the random motion of absorbers with respect to quasars.

  20. The Doppler Effect: A Consideration of Quasar Redshifts.

    Science.gov (United States)

    Gordon, Kurtiss J.

    1980-01-01

    Provides information on the calculation of the redshift to blueshift ratio introduced by the transverse Doppler effect at relativistic speeds. Indicates that this shift should be mentioned in discussions of whether quasars are "local" rather than "cosmological" objects. (GS)

  1. On the Iwasawa-Taniguchi effect of radio-quiet AGN

    Directory of Open Access Journals (Sweden)

    S. Bianchi

    2008-01-01

    Full Text Available La existencia de una anticorrelación entre la anchura equivalente (EW de la línea de emisión de hierro Kα y la luminosidad 2-10 keV (el efecto X-ray Baldwin ó Iwasawa-Taniguchi ha sido debatida en los últimos años. Nuestro objetivo es someter a prueba este resultado, utilizando el mayor catálogo de AGN ‘radio callados’ con espectros de alta calidad en rayos-X que ha sido publicado hasta la fecha. Nuestro catálogo comprende 157 fuentes. Buscamos una relación entre la EW de la línea de hierro con la luminosidad en rayos X, y también con la masa del agujero negro, el cociente de Eddington y la distancia cosmológica. Los datos aquí presentados han sido analizados homogéneamente, todos los espectros son del mismo instrumento y tienen una relación señal-ruido alta. El ajuste lineal entre la EW y la luminosidad 2-10 keV es muy significativo y produce log(EW = (1.73 +-0.03+(-0.17 +- 0.03 log(LX, donde EW es la EW de la línea de hierro neutro Kα en eV y LX es la luminosidad 2-10 keV en unidades de 10 44 erg sֿ¹. La anticorrelación con el cociente de Eddington es también muy significativa, pero no hay una clara dependencia de la EW del hierro con la masa del agujero negro.

  2. The geometry of radio-quiet AGN studied with X-ray polarimetry

    Science.gov (United States)

    Matt, Giorgio

    2016-07-01

    Our current X-ray view of AGN in the local Universe is based on spectroscopic, imaging and timing data. In this talk I will discuss the importance of adding the polarimetric view. The geometry of the matter around the black hole (from the X-ray emitting corona to more distant circumnuclear matter) can be probed by X-ray polarimetry. Observational perspectives in view of the X-ray polarimetric missions currently under study at NASA and ESA will be also discussed.

  3. The nature of the radio-quiet compact X-ray source in SNR RCW 103

    OpenAIRE

    Gotthelf, E. V.; Petre, R.; Hwang, U.

    1997-01-01

    We consider the nature of the elusive neutron star candidate 1E~161348-5055 using X-ray observations obtained with the ASCA Observatory. The compact X-ray source is centered on the shell-type Galactic supernova remnant RCW103 and has been interpreted as a cooling neutron star associated with the remnant. The X-ray spectrum of the remnant shell can be characterized by a non-equilibrium ionization (NEI) thermal model for a shocked plasma of temperature kT ~ 0.3 keV. The spectrum falls off rapid...

  4. Parsec-scale jet properties of the gamma-ray quasar 3C 286

    CERN Document Server

    An, T; Zhao, W; Mohan, P; Cheng, X -P; Cui, Y -Z; Zhang, Z -L

    2016-01-01

    The quasar 3C~286 is one of two compact steep spectrum sources detected by the {\\it Fermi}/LAT. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the $\\gamma$-ray emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at various frequencies reveal a one-sided core--jet structure extending to the southwest at a projected distance of $\\sim$1 kpc. The component at the jet base showing an inverted spectrum is identified as the core, with a mean brightness temperature of $2.8\\times 10^{9}$~K. The jet bends at about 600 pc (in projection) away from the core, from a position angle of $-135^\\circ$ to $-115^\\circ$. Based on the available VLBI data, we inferred the proper motion speed of the inner jet as $0.013 \\pm 0.011$ mas yr$^{-1}$ ($\\beta_{\\rm app} = 0.6 \\pm 0.5$), corresponding to a jet speed of about $0.5\\,c$ at an inclination angle of $48^\\circ$ between the jet and the line of sight of the observer. The brightness temperature, jet speed an...

  5. From local active galactic nuclei to early quasars

    Energy Technology Data Exchange (ETDEWEB)

    Cavaliere, A.; Giallongo, E.; Vagnetti, F.

    1985-09-15

    To close the gap between the local luminosity function of the optically selected active galactic nuclei and the population properties of distant (z< or approx. =2) quasars, we propose a model of differential luminosity evolution which is astrophysically based and contains a minimal number of free parameters. We discuss the advantages of the model and its predictions, and indicate how to extend it for z > 2 to cover the beginning of the quasar era.

  6. Quasar absorption spectra and the structure of the universe

    International Nuclear Information System (INIS)

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed

  7. Quasar absorption spectra and the structure of the universe

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.

    1984-03-01

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed.

  8. Fifty Years of Quasars: Physical Insights and Potential for Cosmology

    Science.gov (United States)

    Sulentic, J. W.; Marziani, P.; Dultzin, D.; D'Onofrio, M.; del Olmo, A.

    2014-12-01

    Last year (2013) was more or less the 50th anniversary of the discovery of quasars. It is an interesting time to review what we know (and don't know) about them both empirically and theoretically. These compact sources involving line emitting plasma show extraordinary luminosities extending to one thousand times that of our Milky Way in emitting volumes of a few solar system diameters (log Lboi= 44.0 - 48.0 erg s-1: D=1-3 light months ~ 103 - 104 gravitational radii). The advent of 8-10 meter class telescopes enables us to study them spectroscopically in ever greater detail. In 2000 we introduced a 4D Eigenvector 1 parameters space involving optical, UV and X- ray measures designed to serve as a 4D equivalent of the 2D H-R diagram so important for depicting the diversity of stellar types and evolutionary states. This diagram has revealed a principal sequence of quasars distinguished by Eddington ratio (proportional to the accretion rate per unit mass). Thus while stellar differences are primarily driven by the mass of a star, quasar differences are apparently driven by the ratio of luminosity-to-mass. Out of this work has emerged the concept of two quasars populations A and B separated at Eddington ratio around 0.2 which maximizes quasar multispectral differences. The mysterious 8% of quasars that are radio-loud belong to population B which are the lowest accretors with the largest black hole masses. Finally we consider the most extreme population A quasars which are the highest accretors and in some cases are among the youngest quasars. We describe how these sources might be exploited as standard candles for cosmology.

  9. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    International Nuclear Information System (INIS)

    We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

  10. Slicing the Torus: Obscuring Structures in Quasars

    Science.gov (United States)

    Elvis, Martin

    2012-07-01

    Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas. It is normally assumed that the obscuration occurs in an oblate "obscuring torus", that begins at the radius at which the most refractive dust can remain solid. The most famous form of this torus is a donut-shaped region of molecular gas with a large scale-height. While this model is elegant and accounts for many phenomena at once, it does not hold up to detailed tests. Instead the obscuration in AGNs must occur on a wide range of scales and be due to a minimum of three physically distinct absorbers. Slicing the "torus" into these three regions will allow interesting physics of the AGN to be extracted.

  11. Slicing the Torus: Obscuring Structures in Quasars

    International Nuclear Information System (INIS)

    Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas. It is normally assumed that the obscuration occurs in an oblate 'obscuring torus', that begins at the radius at which the most refractive dust can remain solid. The most famous form of this torus is a donut-shaped region of molecular gas with a large scale-height. While this model is elegant and accounts for many phenomena at once, it does not hold up to detailed tests. Instead the obscuration in AGNs must occur on a wide range of scales and be due to a minimum of three physically distinct absorbers. Slicing the 'torus' into these three regions will allow interesting physics of the AGN to be extracted.

  12. Slicing the Torus: Obscuring Structures in Quasars

    CERN Document Server

    Elvis, Martin

    2012-01-01

    Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas. It is normally assumed that the obscuration occurs in an oblate "obscuring torus", that begins at the radius at which the most refractive dust can remain solid. The most famous form of this torus is a donut-shaped region of molecular gas with a large scale-height. While this model is elegant and accounts for many phenomena at once, it does not hold up to detailed tests. Instead the obscuration in AGNs must occur on a wide range of scales and be due to a minimum of three physically distinct absorbers. Slicing the "torus" into these three regions will allow interesting physics of the AGN to be extracted.

  13. Measuring the dark energy with quasar clustering

    CERN Document Server

    Calvão, M O; Waga, I

    2002-01-01

    We show, through Monte Carlo simulations, that the Alcock-Pazynski test, as applied to quasar clustering, is a powerful tool to probe the cosmological density and equation of state parameters, Omega_{m0}, Omega_{x0} and w. By taking into account peculiar velocity corrections to the correlation function we obtain, for the Two-Degree Field QSO Redshift Survey (2QZ), the predicted 1\\sigma and 2\\sigma confidence contours. It turns out that the test is competitive with future supernova and galaxy number count ones, besides being complementary to them, for fixed curvature. In particular, we find out that it is especially sensitive to the difference Omega_{m0}-Omega_{Lambda 0}, thus being ideal to combine with CMB results.

  14. Quasar Variability in the Mid-Infrared

    Science.gov (United States)

    Kozłowski, Szymon; Kochanek, Christopher S.; Ashby, Matthew L. N.; Assef, Roberto J.; Brodwin, Mark; Eisenhardt, Peter R.; Jannuzi, Buell T.; Stern, Daniel

    2016-02-01

    The Decadal IRAC Boötes Survey is a mid-IR variability survey of the ˜9 sq. deg. of the NDWFS Boötes Field and extends the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5 μm. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable active galactic nuclei (AGNs) for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ˜1500 spectroscopically confirmed AGNs using single power-law structure functions (SFs), which we find to be steeper (index γ ≈ 0.45) than in the optical (γ ≈ 0.3), leading to much lower amplitudes at short time-lags. This provides evidence for large emission regions, smoothing out any fast UV/optical variations, as the origin of infrared quasar variability. The mid-IR AGN SF slope γ seems to be uncorrelated with both the luminosity and rest-frame wavelength, while the amplitude shows an anti-correlation with the luminosity and a correlation with the rest-frame wavelength.

  15. High-brightness electron injectors

    International Nuclear Information System (INIS)

    Free-electron laser (FEL) oscillators and synchrotron light sources require pulse trains of high peak brightness and, in some applications, high-average power. Recent developments in the technology of photoemissive and thermionic electron sources in rf cavities for electron-linac injector applications offer promising advances over conventional electron injectors. Reduced emittance growth in high peak-current electron injectors may be achieved by using high field strengths and by linearizing the radial component of the cavity electric field at the expense of lower shunt impedance

  16. High brightness beams and applications

    International Nuclear Information System (INIS)

    This paper describes the present research on attaining intense bright electron beams. Thermionic systems are briefly covered. Recent and past results from the photoinjector programs are given. The performance advantages and difficulties presently faced by researchers using photoinjectors is discussed. The progress that has been made in photocathode materials, both in lifetime and quantum efficiency, is covered. Finally, a discussion of emittance measurements of photoinjector systems and how the measurement is complicated by the non-thermal nature of the electron beam is presented

  17. Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales

    CERN Document Server

    Hennawi, J F; Oguri, M; Inada, N; Richards, G T; Pindor, B; Schneider, D P; Becker, R H; Gregg, M D; Hall, P B; Johnston, D E; Fan, X; Burles, S; Schlegel, D J; Gunn, J E; Lupton, R; Bahcall, Neta A; Brunner, R J; Brinkmann, J; Hennawi, Joseph F.; Strauss, Michael A.; Oguri, Masamune; Inada, Naohisa; Richards, Gordon T.; Pindor, Bartosz; Schneider, Donald P.; Becker, Robert H.; Gregg, Michael D.; Hall, Patrick B.; Johnston, David E.; Fan, Xiaohui; Burles, Scott; Schlegel, David J.; Gunn, James E.; Lupton, Robert; Bahcall, Neta A.; Brunner, Robert J.; Brinkman, Jon

    2006-01-01

    We present a sample of 218 new quasar pairs with proper transverse separations R_prop 3 Mpc/h quasar correlation function, extrapolated down as a power law to the separations probed by our binaries. The excess grows to ~ 30 at R_prop ~ 10 kpc/h, and provides compelling evidence that the quasar autocorrelation function gets progressively steeper on sub-Mpc scales. This small scale excess can likely be attributed to dissipative interaction events which trigger quasar activity in rich environments. Recent small scale measurements of galaxy clustering and quasar-galaxy clustering are reviewed and discussed in relation to our measurement of small scale quasar clustering.

  18. Quasar Structure Effects on the VLBI Reference Frame: The Case of 1144 - 379

    Science.gov (United States)

    Shabala, S.; Titov, O.; Lovell, J.; McCallum, J.; Blanchard, J.; Watson, C.; Dickey, J.

    2012-12-01

    The structure and variability of quasars used in geodetic VLBI has a significant impact on geodetic solutions. We investigate these effects in the case of ICRF2 quasar 1144 - 379. We find that the precision of geodetic solutions is directly related to the multi-frequency temporal variability in the quasar flux density. Worst solutions are found when the quasar is observed at different evolutionary stages at S and X-bands; this introduces significant error into ionospheric corrections. Our results suggests that quasar variability can be more important than quasar structure. Accurate calibration of IVS amplitude data is crucial for mitigation of these effects.

  19. The near-to-mid infrared spectrum of quasars

    Science.gov (United States)

    Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena; Mateos, Silvia

    2016-08-01

    We analyse a sample of 85 luminous (log (νLν(3µm)/erg s-1)>45.5) quasars with restframe ˜2-11 µm spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disk and two blackbodies for the dust emission successfully reproduces the 0.1-10 µm spectral energy distributions (SEDs). Excess emission at 1-2 µm over the best-fitting model suggests that hotter dust is necessary in addition to the ˜1200 K blackbody and the disk to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disk and in the relative strength of the disk and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disk luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the restframe range 0.1-11 µm, and separate templates for the disk and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2-4 µm range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 µm bump.

  20. The Sloan Digital Sky Survey Quasar Catalog: twelfth data release

    CERN Document Server

    Pâris, Isabelle; Ross, Nicholas P; Myers, Adam D; Aubourg, Éric; Streblyanska, Alina; Bailey, Stephen; Armengaud, Éric; Palanque-Delabrouille, Nathalie; Yèche, Christophe; Hamann, Fred; Strauss, Michael A; Albareti, Franco D; Bovy, Jo; Bizyaev, Dmitry; Brandt, W Niel; Brusa, Marcella; Buchner, Johannes; Comparat, Johan; Croft, Rupert A C; Dwelly, Tom; Fan, Xiaohui; Font-Ribera, Andreu; Ge, Jian; Georgakakis, Antonis; Hall, Patrick B; Jian, Linhua; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; McMahon, Richard G; Menzel, Marie-Luise; Merloni, Andrea; Nandra, Kirpal; Noterdaeme, Pasquier; Oravetz, Daniel; Pan, Kaike; Pieri, Matthew M; Prada, Francisco; Salvato, Mara; Schlegel, David J; Schneider, Donald P; Simmons, Audrey; Viel, Matteo; Weinberg, David H; Zhu, Liu

    2016-01-01

    We present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the SDSS-III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities Mi[z=2]2.15 is about an order of magnitude greater than the number of z>2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 29,580 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and PTF multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properti...

  1. An extinction curve template for intrinsically reddened quasars

    CERN Document Server

    Zafar, Tayyaba; Watson, Darach; Fynbo, Johan P U; Krogager, Jens-Kristian; Zafar, Nosheen; Saturni, Francesci G; Geier5, Stefan; Venemans, Bram P

    2015-01-01

    We analyze the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 $<$ $z$ $<$ 2.13 to investigate dust extinction properties. The sample presented in this work is obtained from the High $A_V$ Quasar (HAQ) survey. The quasar candidates were selected from the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New Technology Telescope (NTT). To study dust extinction curves intrinsic to the quasars, from the HAQ survey we selected 16 cases where the Small Magellanic Cloud (SMC) law could not provide a good solution to the spectral energy distributions (SEDs). We derived the extinction curves using Fitzpatrick & Massa 1986 (FM) law by comparing the observed SEDs to the combined quasar template from Vanden Berk et al. 2001 and Glikman et al. 2006. The derived extinction, $A_V$, ranges from 0.2-1.0 mag. All the individual extinction curves of our quasars are steeper ($...

  2. X-ray Absorption of High Redshift Quasars

    CERN Document Server

    Eitan, Assaf

    2013-01-01

    Soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astro-physical context. We construct the largest sample to date of 58 high redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (> 1800). We measure the optical depth tau at 0.5 keV, and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars drive their observed absorption, e.g., redshift, radio luminosity, radio loudness, or the X-ray luminosity. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption, and with a comparison sample of gamma ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. On...

  3. Black hole masses and enrichment of z ~ 6 SDSS quasars

    CERN Document Server

    Kurk, Jaron D; Fan, Xiaohui; Jiang, Linhua; Riechers, Dominik A; Rix, Hans-Walter; Pentericci, Laura; Strauss, Michael A; Carilli, Chris; Wagner, Stefan

    2007-01-01

    We present sensitive near-infrared spectroscopic observations for a sample of five z ~ 6 quasars. These are amongst the most distant, currently known quasars in the universe. The spectra have been obtained using ISAAC at the VLT and include the CIV, MgII and FeII lines. We measure the FeII/MgII line ratio, as an observational proxy for the Fe/alpha element ratio. We derive a ratio of 2.7+/-0.8 for our sample, which is similar to that found for lower redshift quasars, i.e., we provide additional evidence for the lack of evolution in the FeII/MgII line ratio of quasars up to the highest redshifts. This result demonstrates that the sample quasars must have undergone a major episode of iron enrichment in less than one Gyr and star formation must have commenced at z > 8. The linewidths of the MgII and CIV lines give two estimates for the black hole masses. A third estimate is given by assuming that the quasars emit at their Eddington luminosity. The derived masses using these three methods agree well, implying tha...

  4. Dissecting the Quasar Main Sequence: Insight from Host Galaxy Properties

    Science.gov (United States)

    Sun, Jiayi; Shen, Yue

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/LEdd) of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ* (hence, the BH mass via the M-σ* relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ* systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ* on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  5. The Sloan Digital Sky Survey quasar catalog: ninth data release

    CERN Document Server

    Pâris, Isabelle; Aubourg, Eric; Bailey, Stephen; Ross, Nicholas P; Myers, Adam D; Strauss, Michael A; Anderson, Scott F; Arnau, Eduard; Bautista, Julian; Bizyaev, Dmitry; Bolton, Adam S; Bovy, Jo; Brandt, William N; Brewington, Howard; Brownstein, Joel R; Busca, Nicolas; Capellupo, Daniel; Carithers, William; Croft, Rupert A C; Dawson, Kyle; Delubac, Timothée; Ebelke, Garrett; Eisenstein, Daniel J; Engelke, Philip; Fan, Xiaohui; Ak, Nur Filiz; Finley, Hayley; Font-Ribera, Andreu; Ge, Jian; Gibson, Robert R; Hall, Patrick B; Hamann, Fred; Hennawi, Joseph F; Ho, Shirley; Hogg, David W; Ivezic, Zeljko; Jiang, Linhua; Kimball, Amy E; Kirkby, David; Kirkpatrick, Jessica A; Lee, Khee-Gan; Goff, Jean-Marc Le; Lundgren, Britt; MacLeod, Chelsea L; Malanushenko, Elena; Malanushenko, Viktor; Maraston, Claudia; McGreer, Ian D; McMahon, Richard G; Miralda-Escudé, Jordi; Muna, Demitri; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pan, Kaike; Perez-Fournon, Ismaël; Pieri, Matthew M; Richards, Gordon T; Rollinde, Emmanuel; Sheldon, Erin S; Schlegel, David J; Schneider, Donald P; Slosar, Anze; Shelden, Alaina; Shen, Yue; Simmons, Audrey; Snedden, Stephanie; Suzuki, Nao; Tinker, Jeremy; Viel, Matteo; Weaver, Benjamin A; Weinberg, David H; White, Martin; Wood-Vasey, W Michael; Yèche, Christophe

    2012-01-01

    We present the Data Release 9 Quasar (DR9Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the survey, are spectrocopically confirmed as quasars via visual inspection, have luminosities Mi[z=2]2.15$ (61,931) is ~2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 broad absorption line quasars and gives their characteristics. For each object the catalog presents five-band (u,g,r,i,z) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys.

  6. DISSECTING THE QUASAR MAIN SEQUENCE: INSIGHT FROM HOST GALAXY PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiayi [Tsinghua Center for Astrophysics, Department of Physics, Tsinghua University, Beijing 100084 (China); Shen, Yue [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L{sub Edd}) of the black hole (BH) accretion. Shen and Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ{sub *} (hence, the BH mass via the M–σ{sub *} relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ{sub *} systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ{sub *} on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  7. Eight new quasars discovered by LAMOST in one extragalactic field

    CERN Document Server

    Wu, Xue-Bing; Chen, Zhaoyu; Zuo, Wenwen; Zhao, Yongheng; Luo, Ali; Bai, Zhongrui; Chen, Jianjun; Zhang, Haotong; Yan, Hongliang; Ren, Juanjuan; Sun, Shiwei; Wu, Hong; Zhang, Yong; Li, Yeping; Lu, Qishuai; Wang, You; Ni, Jijun; Wang, Hai; Kong, Xu; Shen, Shiyin

    2010-01-01

    We report the discovery of eight new quasars in one extragalactic field (five degree centered at RA=$08^h58^m08.2^s$, Dec=$01^o32'29.7''$) with the LAMOST commissioning observations on December 18, 2009. These quasars, with $i$ magnitudes from 16.21 to 19.13 and redshifts from 0.898 to 2.773, have optical colors quite similar as stars and were not targeted in the SDSS spectroscopic survey. Seven of them were selected as quasar candidates by a newly proposed criterion involving both near-IR and optical colors. Two of them were found in the 'redshift desert' for quasars ($z$ from 2.2 to 3), indicating that the new criterion is efficient for recovering the missing quasars with similar optical colors as stars. Although LAMOST met many problems including the the low accuracy of fiber positioning and poor dom seeing condition during the commissioning observations, we were still able to identify other 38 known SDSS quasars in this field, with $i$ magnitudes from 16.24 to 19.10 and redshifts from 0.297 to 4.512. Our ...

  8. Sources of the Radio Background Considered

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; /KIPAC, Menlo Park /Stanford U.; Stawarz, L.; /KIPAC, Menlo Park /Stanford U. /Jagiellonian U., Astron. Observ.; Lawrence, A.; /Edinburgh U., Inst. Astron. /KIPAC, Menlo Park /Stanford U.; Petrosian, V.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.

    2011-08-22

    We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio background is produced by radio point sources that dominate at sub {mu}Jy fluxes. We show that a truly diffuse background produced by elections far from galaxies is ruled out because such energetic electrons would overproduce the observed X-ray/{gamma}-ray background through inverse Compton scattering of the other photon fields. Unrecognized flux from low surface brightness regions of extended radio sources, or moderate flux sources missed entirely by radio source count surveys, cannot explain the bulk of the observed background, but may contribute as much as 10%. We consider both radio supernovae and radio quiet quasars as candidate sources for the background, and show that both fail to produce it at the observed level because of insufficient number of objects and total flux, although radio quiet quasars contribute at the level of at least a few percent. We conclude that the most important population for production of the background is likely ordinary starforming galaxies above redshift 1 characterized by an evolving radio far-infrared correlation, which increases toward the radio loud with redshift.

  9. Sources of the Radio Background Considered

    International Nuclear Information System (INIS)

    We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio background is produced by radio point sources that dominate at sub μJy fluxes. We show that a truly diffuse background produced by elections far from galaxies is ruled out because such energetic electrons would overproduce the observed X-ray/γ-ray background through inverse Compton scattering of the other photon fields. Unrecognized flux from low surface brightness regions of extended radio sources, or moderate flux sources missed entirely by radio source count surveys, cannot explain the bulk of the observed background, but may contribute as much as 10%. We consider both radio supernovae and radio quiet quasars as candidate sources for the background, and show that both fail to produce it at the observed level because of insufficient number of objects and total flux, although radio quiet quasars contribute at the level of at least a few percent. We conclude that the most important population for production of the background is likely ordinary starforming galaxies above redshift 1 characterized by an evolving radio far-infrared correlation, which increases toward the radio loud with redshift.

  10. The Bright New Financial System

    Directory of Open Access Journals (Sweden)

    Associate Professor Adela Coman

    2009-05-01

    Full Text Available By the end of 2008, Mr. Paul Volcker gave financiers a devastating critique. “For all its talented participants, for all its rich rewards” he said, the “bright new financial system” has “failed the test of the marketplace”.In light of the events of recent weeks, it is hard to disagree. A financial system that ends up with the government taking over some of its biggest institutions in serial weekend rescues and which requires the promise of 700 billion dollars in public money to stave off catastrophe is not a trustworthy system. The disappearance of all five big American investment banks – either by bankruptcy or rebirth as commercial banks – is powerful evidence that Wall Street failed “the test of the marketplace”. Something went wrong.But what exactly and why? A more serious analysis needs to distinguish between three separate questions: what is Mr. Volcker’s “bright new financial system”? Second, how far was today’s mess created by instabilities that are inseparable from modern finance and how far was it fuelled by other errors and distortions? Third, to the extent that modern finance does bear the blame, what is the balance between its costs and its benefits and how can it be improved?

  11. The quasar-galaxy cross SDSS J1320+1644: A probable large-separation lensed quasar

    CERN Document Server

    Rusu, Cristian E; Iye, Masanori; Inada, Naohisa; Kayo, Issha; Shin, Min-Su; Sluse, Dominique; Strauss, Michael A

    2012-01-01

    We report the discovery of a pair of quasars at $z=1.487$, with a separation of $8\\farcs585\\pm0\\farcs002$. Subaru Telescope infrared imaging reveals the presence of an elliptical and a disk-like galaxy located almost symmetrically between the quasars, creating a cross-like configuration. Based on absorption lines in the quasar spectra and the colors of the galaxies, we estimate that both galaxies are located at redshift $z=0.899$. This, as well as the similarity of the quasar spectra, suggests that the system is a single quasar multiply imaged by a galaxy group or cluster acting as a gravitational lens, although the possibility of a binary quasar cannot be fully excluded. We show that the gravitational lensing hypothesis implies these galaxies are not isolated, but must be embedded in a dark matter halo of virial mass $\\sim 4 \\times 10^{14}\\ h_{70}^{-1}\\ {M}_\\odot$ assuming an NFW model with a concentration parameter of $c_{vir}=6$, or a singular isothermal sphere profile with a velocity dispersion of $\\sim 6...

  12. MOLECULAR GAS IN z ∼ 6 QUASAR HOST GALAXIES

    International Nuclear Information System (INIS)

    We report our new observations of redshifted carbon monoxide emission from six z ∼ 6 quasars, using the IRAM Plateau de Bure Interferometer. CO (6-5) or (5-4) line emission was detected in all six sources. Together with two other previous CO detections, these observations provide unique constraints on the molecular gas emission properties in these quasar systems close to the end of the cosmic re-ionization. Complementary results are also presented for low-J CO lines observed at the Green Bank Telescope and the Very Large Array, and dust continuum from five of these sources with the SHARC-II bolometer camera at the Caltech Submillimeter Observatory. We then present a study of the molecular gas properties in our combined sample of eight CO-detected quasars at z ∼ 6. The detections of high-order CO line emission in these objects indicates the presence of highly excited molecular gas, with estimated masses on the order of 1010 Msun within the quasar host galaxies. No significant difference is found in the gas mass and CO line width distributions between our z ∼ 6 quasars and samples of CO-detected 1.4 ≤ z ≤ 5 quasars and submillimeter galaxies. Most of the CO-detected quasars at z ∼ 6 follow the far-infrared-CO luminosity relationship defined by actively star-forming galaxies at low and high redshifts. This suggests that ongoing star formation in their hosts contributes significantly to the dust heating at FIR wavelengths. The result is consistent with the picture of galaxy formation co-eval with supermassive black hole (SMBH) accretion in the earliest quasar-host systems. We investigate the black hole-bulge relationships of our quasar sample, using the CO dynamics as a tracer for the dynamical mass of the quasar host. The median estimated black hole-bulge mass ratio is about 15 times higher than the present-day value of ∼0.0014. This places important constraints on the formation and evolution of the most massive SMBH-spheroidal host systems at the

  13. Testing quasar unification: radiative transfer in clumpy winds

    Science.gov (United States)

    Matthews, J. H.; Knigge, C.; Long, K. S.; Sim, S. A.; Higginbottom, N.; Mangham, S. W.

    2016-05-01

    Various unification schemes interpret the complex phenomenology of quasars and luminous active galactic nuclei (AGN) in terms of a simple picture involving a central black hole, an accretion disc and an associated outflow. Here, we continue our tests of this paradigm by comparing quasar spectra to synthetic spectra of biconical disc wind models, produced with our state-of-the-art Monte Carlo radiative transfer code. Previously, we have shown that we could produce synthetic spectra resembling those of observed broad absorption line (BAL) quasars, but only if the X-ray luminosity was limited to 1043 erg s-1. Here, we introduce a simple treatment of clumping, and find that a filling factor of ˜0.01 moderates the ionization state sufficiently for BAL features to form in the rest-frame UV at more realistic X-ray luminosities. Our fiducial model shows good agreement with AGN X-ray properties and the wind produces strong line emission in, e.g., Lyα and C IV 1550 Å at low inclinations. At high inclinations, the spectra possess prominent LoBAL features. Despite these successes, we cannot reproduce all emission lines seen in quasar spectra with the correct equivalent-width ratios, and we find an angular dependence of emission line equivalent width despite the similarities in the observed emission line properties of BAL and non-BAL quasars. Overall, our work suggests that biconical winds can reproduce much of the qualitative behaviour expected from a unified model, but we cannot yet provide quantitative matches with quasar properties at all viewing angles. Whether disc winds can successfully unify quasars is therefore still an open question.

  14. How Bright Can Supernovae Get?

    Science.gov (United States)

    Kohler, Susanna

    2016-04-01

    Supernovae enormous explosions associated with the end of a stars life come in a variety of types with different origins. A new study has examined how the brightest supernovae in the Universe are produced, and what limits might be set on their brightness.Ultra-Luminous ObservationsRecent observations have revealed many ultra-luminous supernovae, which haveenergies that challenge our abilities to explain them usingcurrent supernova models. An especially extreme example is the 2015 discovery of the supernova ASASSN-15lh, which shone with a peak luminosity of ~2*1045 erg/s, nearly a trillion times brighter than the Sun. ASASSN-15lh radiated a whopping ~2*1052 erg in the first four months after its detection.How could a supernova that bright be produced? To explore the answer to that question, Tuguldur Sukhbold and Stan Woosley at University of California, Santa Cruz, have examined the different sources that could produce supernovae and calculated upper limits on the potential luminosities ofeach of these supernova varieties.Explosive ModelsSukhbold and Woosley explore multiple different models for core-collapse supernova explosions, including:Prompt explosionA stars core collapses and immediately explodes.Pair instabilityElectron/positron pair production at a massive stars center leads to core collapse. For high masses, radioactivity can contribute to delayed energy output.Colliding shellsPreviously expelled shells of material around a star collide after the initial explosion, providing additional energy release.MagnetarThe collapsing star forms a magnetar a rapidly rotating neutron star with an incredibly strong magnetic field at its core, which then dumps energy into the supernova ejecta, further brightening the explosion.They then apply these models to different types of stars.Setting the LimitThe authors show that the light curve of ASASSN-15lh (plotted in orange) can be described by a model (black curve) in which a magnetar with an initial spin period of 0.7 ms

  15. [Bright light therapy for elderly].

    Science.gov (United States)

    Okawa, Masako

    2015-06-01

    Bright light therapy (BLT) holds considerable promise for sleep problems in the elderly. BLT for community-dwelling patients with Alzheimer's disease showed significant improvement in sleep parameters. In the institutional setting, BLT was effective in reducing daytime nap duration. Morning BLT was found to advance the peak circadian rhythm and increase activity level in daytime and melatonin level at night. Light therapy could be used in combination with other nonpharmacological methods such as social activities, outside walking, physical exercises, which showed greater effects than independent BLT on sleep and cognitive function. BLT treatment strategy was proposed in the present paper. We should pay more attentions to BLT in community setting for mental and physical well-being. PMID:26065132

  16. On the nature of bright compact radio sources at z>4.5

    Science.gov (United States)

    Coppejans, Rocco; Frey, Sándor; Cseh, Dávid; Müller, Cornelia; Paragi, Zsolt; Falcke, Heino; Gabányi, Krisztina É.; Gurvits, Leonid I.; An, Tao; Titov, Oleg

    2016-09-01

    High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here we report on observations of an additional ten z > 4.5 sources at 1.7 and 5 GHz with the European VLBI Network (EVN), thereby increasing the number of imaged sources by 50 per cent. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z > 4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis (unbeamed) radio sources with rest-frame self-absorption peaks at or below GHz frequencies and that these sources can be classified as gigahertz peaked-spectrum (GPS) and megahertz peaked-spectrum (MPS) sources.

  17. On the nature of bright compact radio sources at z>4.5

    CERN Document Server

    Coppejans, Rocco; Cseh, Dávid; Müller, Cornelia; Paragi, Zsolt; Falcke, Heino; Gabányi, Krisztina É; Gurvits, Leonid I; An, Tao; Titov, Oleg

    2016-01-01

    High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here we report on observations of an additional ten z>4.5 sources at 1.7 and 5 GHz with the European VLBI Network (EVN), thereby increasing the number of imaged sources by 50%. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z>4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis ...

  18. Hints on the Broad Line Region Structure of Quasars at High and Low Luminosities

    Science.gov (United States)

    Marziani, Paola; Sulentic, Jack W.; Zamfir, Sebastian; Negrete, C. A.; Dultzin, Deborah

    2011-08-01

    Quasars show a considerable spectroscopic diversity. However, the variety of quasar spectra at low redshifts is non-random: a principal component analysis applied to large samples customarily identifies two main eigenvectors. In this contribution we show that the range of quasar optical spectral properties observed at low-z\\ and associated with the first eigenvector is preserved up to z ≈ 2 in a sample of high luminosity quasars. We also describe two major luminosity effects.

  19. Quantum communication with macroscopically bright nonclassical states.

    Science.gov (United States)

    Usenko, Vladyslav C; Ruppert, Laszlo; Filip, Radim

    2015-11-30

    We analyze homodyne detection of macroscopically bright multimode nonclassical states of light and propose their application in quantum communication. We observe that the homodyne detection is sensitive to a mode-matching of the bright light to the highly intense local oscillator. Unmatched bright modes of light result in additional noise which technically limits detection of Gaussian entanglement at macroscopic level. When the mode-matching is sufficient, we show that multimode quantum key distribution with bright beams is feasible. It finally merges the quantum communication with classical optical technology of visible beams of light. PMID:26698776

  20. Photometric Classification of quasars from RCS-2 using Random Forest

    CERN Document Server

    Carrasco, D; Pichara, K; Anguita, T; Murphy, D N A; Gilbank, D G; Gladders, M D; Yee, H K C; Hsieh, B C; López, S

    2014-01-01

    We describe the construction of a quasar catalog containing 91,842 candidates derived from analysis of imaging data with a Random Forest algorithm. Using spectroscopically-confirmed stars and quasars from the SDSS as a training set, we blindly search the RCS-2 (~750 deg^2) imaging survey. From a source catalogue of 1,863,970 RCS-2 point sources, our algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colours. Exploiting NUV GALEX measurements available for a subset 16,898 of these objects, we refine the classifier by adding NUV-optical colours to the algorithm's search. An additional subset (comprising 13% of the source catalog) features WISE coverage; we explore the effect of including W1 and W2 bands on the performance of the algorithm. Upon analysing all RCS-2 point sources, the algorithm identified 85,085 quasar candidates, with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 90.4% and a recall (the fraction of true ...

  1. Dissecting the quasar main sequence: insight from host galaxy properties

    CERN Document Server

    Sun, Jiayi

    2015-01-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical FeII strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L_Edd) of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing FeII strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion sigma* (hence the BH mass via the M-sigma* relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, sigma* systematically decreases with increasing FeII strength, confirming that Eddington ratio increases with FeII strength. We also found that at fixed luminosity and FeII strength, there is little dependence of sigma* on the broad Hbeta FWHM. These new results reinforce the framework put forward by Shen & H...

  2. Quasar Feedback: the Missing Link in Structure Formation

    CERN Document Server

    Scannapieco, E S; Scannapieco, Evan

    2004-01-01

    We consider the impact of quasar outflows on structure formation. As quasars are powered by supermassive black holes, whose masses scale roughly with the depth of the potential well of their host galaxies (M_BH \\propto M_galaxy^5/3), they dominate over starbursts (E_starburst \\propto M_galaxy) in powering outflows from the large galaxies that form at low redshifts. Using a simple analytical model for the quasar distribution, coupled with a one-dimensional Sedov-Taylor model, we are able to make robust statements as to the impact of these outflows on structure formation. As large regions of the intergalactic medium (IGM) are heated above a critical entropy of approximately 100 keV cm^2, cooling become impossible within them, regardless of changes in density. On quasar scales, this has the effect of inhibiting further formation, resulting in their observed fall-off in number densities below z ~ 2. On galaxy scales, quasar feedback fixes the turn-over scale in the galaxy luminosity function (L_*) as the nonlinea...

  3. Time Variability of Quasars: the Structure Function Variance

    Science.gov (United States)

    MacLeod, C.; Ivezić, Ž.; de Vries, W.; Sesar, B.; Becker, A.

    2008-12-01

    Significant progress in the description of quasar variability has been recently made by employing SDSS and POSS data. Common to most studies is a fundamental assumption that photometric observations at two epochs for a large number of quasars will reveal the same statistical properties as well-sampled light curves for individual objects. We critically test this assumption using light curves for a sample of ~2,600 spectroscopically confirmed quasars observed about 50 times on average over 8 years by the SDSS stripe 82 survey. We find that the dependence of the mean structure function computed for individual quasars on luminosity, rest-frame wavelength and time is qualitatively and quantitatively similar to the behavior of the structure function derived from two-epoch observations of a much larger sample. We also reproduce the result that the variability properties of radio and X-ray selected subsamples are different. However, the scatter of the variability structure function for fixed values of luminosity, rest-frame wavelength and time is similar to the scatter induced by the variance of these quantities in the analyzed sample. Hence, our results suggest that, although the statistical properties of quasar variability inferred using two-epoch data capture some underlying physics, there is significant additional information that can be extracted from well-sampled light curves for individual objects.

  4. Dissecting the complex environment of a distant quasar with MUSE

    CERN Document Server

    Husband, K; Stanway, E R; Lehnert, M D

    2015-01-01

    High redshift quasars can be used to trace the early growth of massive galaxies and may be triggered by galaxy-galaxy interactions. We present MUSE science verification data on one such interacting system consisting of the well-studied z=3.2 PKS1614+051 quasar, its AGN companion galaxy and bridge of material radiating in Lyalpha between the quasar and its companion. We find a total of four companion galaxies (at least two galaxies are new discoveries), three of which reside within the likely virial radius of the quasar host, suggesting that the system will evolve into a massive elliptical galaxy by the present day. The MUSE data are of sufficient quality to split the extended Lyalpha emission line into narrow velocity channels. In these the gas can be seen extending towards each of the three neighbouring galaxies suggesting that the emission-line gas originates in a gravitational interaction between the galaxies and the quasar host. The photoionization source of this gas is less clear but is probably dominate...

  5. Quasar optical variability: searching for interband time delays

    Science.gov (United States)

    Bachev, R. S.

    2009-01-01

    Aims: The main purpose of this paper is to study time delays between the light variations in different wavebands for a sample of quasars. Measuring a reliable time delay for a large number of quasars may help constraint the models of their central engines. The standard accretion disk irradiation model predicts a delay of the longer wavelengths behind the shorter ones, a delay that depends on the fundamental quasar parameters. Since the black hole masses and the accretion rates are approximately known for the sample we use, one can compare the observed time delays with the expected ones. Methods: We applied the interpolation cross-correlation function (ICCF) method to the Giveon et al. sample of 42 quasars, monitored in two (B and R) colors, to find the time lags represented by the ICCF peaks. Different tests were performed to assess the influence of photometric errors, sampling, etc., on the final result. Results: We found that most of the objects show a delay in the red light curve behind the blue one (a positive lag), which on average for the sample is about +4 days (+3 for the median), although the scatter is significant. These results are broadly consistent with the reprocessing model, especially for the well-sampled objects. The normalized time-lag deviations do not seem to correlate significantly with other quasar properties, including optical, radio, or X-ray measurables. On the other hand, many objects show a clear negative lag, which, if real, may have important consequences for the variability models.

  6. Optical variability properties of mini-BAL and NAL quasars

    Science.gov (United States)

    Horiuchi, Takashi; Misawa, Toru; Morokuma, Tomoki; Koyamada, Suzuka; Takahashi, Kazuma; Wada, Hisashi

    2016-08-01

    While narrow absorption lines (NALs) are relatively stable, broad absorption lines (BALs) and mini-BAL systems usually show violent time variability within a few years via a mechanism that is not yet understood. In this study, we examine the variable ionization state (VIS) scenario as a plausible mechanism, as previously suspected. Over three years, we performed photometric monitoring observations of four mini-BAL and five NAL quasars at zem ˜ 2.0-3.1 using the 105 cm Kiso Schmidt Telescope in u, g, and i bands. We also performed spectroscopic monitoring observation of one of our mini-BAL quasars (HS 1603+3820) using the 188 cm Okayama Telescope over the same period as the photometric observations. Our main results are as follows: (1) Structure function (SF) analysis revealed that the quasar UV flux variability over three years was not large enough to support the VIS scenario, unless the ionization condition of outflow gas is very low. (2) There was no crucial difference between the SFs of mini-BAL and NAL quasars. (3) The variability of the mini-BAL and quasar light curves was weakly synchronized with a small time delay for HS 1603+3820. These results suggest that the VIS scenario may need additional mechanisms such as variable shielding by X-ray warm absorbers.

  7. A Variable PV Broad Absorption Line and Quasar Outflow Energetics

    CERN Document Server

    Capellupo, Daniel M; Barlow, Tom A

    2014-01-01

    Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that might exist in all quasars and could play a major role in feedback to galaxy evolution. The viability of BAL outflows as a feedback mechanism depends on their kinetic energies, as derived from the outflow velocities, column densities, and distances from the central quasar. We estimate these quantities for the quasar, Q1413+1143 (redshift $z_e = 2.56$), aided by the first detection of PV $\\lambda\\lambda$1118,1128 BAL variability in a quasar. In particular, PV absorption at velocities where the CIV trough does not reach zero intensity implies that the CIV BAL is saturated and the absorber only partially covers the background continuum source (with characteristic size 22.3 (cm^-2). Variability in the PV and saturated CIV BALs strongly disfavors changes in the ionization as the cause of the BAL variability, but supports models with high-column density BAL clouds moving across our lines of sight. The observed variability time of ...

  8. He II Proximity Effect and the Lifetime of Quasars

    CERN Document Server

    Khrykin, I S; McQuinn, M; Worseck, G

    2015-01-01

    The lifetime of quasars is fundamental for understanding the growth of supermassive black holes, and is an important ingredient in models of the reionization of the intergalactic medium. However, despite various attempts to determine quasar lifetimes, current estimates from a variety of methods are uncertain by orders of magnitude. This work combines cosmological hydrodynamical simulations and 1D radiative transfer to investigate the structure and evolution of the He II Ly$\\alpha$ proximity zones around quasars at $z \\simeq 3-4$. We show that the time evolution in the proximity zone can be described by a simple analytical model for the approach of the He II fraction $x_{\\rm HeII}\\left( t \\right)$ to ionization equilibrium, and use this picture to illustrate how the transmission profile depends on the quasar lifetime, quasar UV luminosity, and the ionization state of helium in the ambient IGM (i.e. the average He II fraction, or equivalently the metagalactic He II ionizing background). A significant degeneracy...

  9. Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars

    CERN Document Server

    Richards, G T; Budavari, T; Fan, X; Gallagher, S C; Hall, P B; Hines, D C; Jester, S; Lacy, M; Papovich, C; Schneider, D P; Storrie-Lombardi, L J; Szalay, A S; Trammell, G B; Vanden Berk, Daniel E; Vestergaard, M; York, D G; Anderson, Scott F.; Berk, Daniel E. Vanden; Budavari, Tamas; Fan, Xiaohui; Hall, Patrick B.; Hines, Dean C.; Jester, Sebastian; Lacy, Mark; Papovich, Casey; Richards, Gordon T.; Schneider, Donald P.; Storrie-Lombardi, Lisa J.; Szalay, Alexander S.; Trammell, George B.; Vestergaard, Marianne; York, Donald G.

    2006-01-01

    We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z=3, with predictions to z=7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGN) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA and ROSAT data where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as a factor of 2 for individual quasars. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to ...

  10. Structure of radiation dominated gravitoturbulent quasar discs

    CERN Document Server

    Shadmehri, Mohsen; Dib, Sami

    2016-01-01

    Self-gravitating accretion discs in a gravitoturbulent state, including radiation and gas pressures, are studied using a set of new analytical solutions. While the Toomre parameter of the disc remains close to its critical value for the onset of gravitational instability, the dimensionless stress parameter is uniquely determined from the thermal energy reservoir of the disc and its cooling rate. Our solutions are applicable to the accretion discs with dynamically important radiation pressure like in the quasars discs. We show that physical quantities of a gravitoturbulent disc in the presence of radiation are significantly modified compared to solutions with only gas pressure. We show that the dimensionless stress parameter is an increasing function of the radial distance so that its steepness strongly depends on the accretion rate. In a disc without radiation its slope is 4.5, however, we show that in the presence of radiation, it varies between 2 and 4.5 depending on the accretion rate and the central mass....

  11. A portable modeler of lensed quasars

    CERN Document Server

    Saha, P; Saha, Prasenjit; Williams, Liliya L.R.

    2004-01-01

    We introduce and implement two novel ideas for modeling lensed quasars. The first idea is to require different lenses to agree about H_0. This means that some models for one lens can be ruled out by data on a different lens. We explain using two worked examples. One example models 1115+080, 1608+656 (time-delay quads) and 1933+503 (a prospective time-delay system) all together, yielding time-delay predictions for the third lens and a 90%-confidence estimate of 1/H_0=14.6_{-1.7}^{+9.4} Gyr (H_0=67_{-26}^{+9} km/s/Mpc) assuming Omega_M=0.3, Omega_Lambda=0.7. The other example models the time-delay doubles 1520+530, 1600+434, 1830-211, and 2149-275, which gives 1/H_0=14.5_{-1.5}^{+3.3} Gyr (H_0=67_{-13}^{+8} km/s/Mpc). Our second idea is to write the whole modeling software as a highly interactive Java applet, which can be used both for coarse-grained results inside a browser and for fine-grained results on a workstation. Several obstacles come up in trying to implement a numerically-intensive method thus, but w...

  12. Quasar Variability in the Mid-Infrared

    CERN Document Server

    Kozlowski, Szymon; Ashby, Matthew L N; Assef, Roberto J; Brodwin, Mark; Eisenhardt, Peter R; Jannuzi, Buell T; Stern, Daniel

    2015-01-01

    The Decadal IRAC Bootes Survey (DIBS) is a mid-IR variability survey of the ~9 sq. deg. of the NDWFS Bootes Field and extnds the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5 microns. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In the mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable AGNs for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ~1500 spectroscopically confirmed AGNs using single power-law structure functions, which we f...

  13. Quasars Probing Quasars VII. The Pinnacle of the Cool Circumgalactic Medium Surrounds Massive z~2 Galaxies

    CERN Document Server

    Prochaska, J Xavier; Hennawi, Joseph F

    2014-01-01

    We survey the incidence and absorption strength of the metal-line transitions CII 1334 and CIV from the circumgalactic medium (CGM) surrounding z~2 quasars, which act as signposts for massive dark matter halos M_halo~10^12.5 Msun. On scales of the virial radius (Mvir~160kpc), we measure a high covering fraction fC=0.73+/-0.10 to strong CII absorption (rest equivalent width W1334>0.2A), implying a massive reservoir of cool (T~10^4K) metal enriched gas. We conservatively estimate a metal mass exceeding 10^8 Msun. We propose these metals trace enrichment of the incipient intragroup/intracluster medium that these halos eventually inhabit. This cool CGM around quasars is the pinnacle amongst galaxies observed at all epochs, as regards covering fraction and average equivalent width of HI Lya and low-ion metal absorption. We argue that the properties of this cool CGM primarily reflect the halo mass, and that other factors such as feedback, star-formation rate, and accretion from the intergalactic medium are secondar...

  14. Nitrogen-deficient and iron-rich associated absorbers with oversolar metallicities towards the quasar HE0141-3932

    CERN Document Server

    Levshakov, S A; Reimers, D; Fechner, C; Janknecht, E; López, S

    2005-01-01

    HE0141-3932 (zem=1.80) is a bright blue radio-quite quasar which reveals an emission line spectrum with an unusually weak Ly-alpha line. In addition, large redshift differences (Delta z=0.05) are observed between high ionization and low ionization emission lines. Absorption systems identified at z=1.78, 1.71, and 1.68 show mild oversolar metallicities (Z ~= 1-2Zsolar) and can be attributed to the associated gas clouds ejected from the circumnuclear region. The joint analysis of the emission and absorption lines leads to the conclusion that this quasar is seen almost pole-on. Its apparent luminosity may be Doppler boosted by ~10 times. The absorbing gas shows high abundance of Fe, Mg, and Al ([Fe, Mg, Al/C] ~= 0.15+/-0.10) along with underabundance of N ([N/C]0 and [Fe/C]<0 at Z ~ Zsolar. Full details of this work are given in Reimers et al. (2005).

  15. Photo-centric variability of quasars caused by variations in their inner structure: Consequences on Gaia measurements

    CERN Document Server

    Popovic, Luka C; Stalevski, Marko; Anton, Sonia; Andrei, Alexandre H; Kovacevic, Jelena; Baes, Maarten

    2011-01-01

    We study the photocenter position variability due to variations in the quasar inner structure. We consider variability in the accretion disk emissivity and torus structure variability due to different illumination by the central source. We discuss possible detection of these effects by Gaia. Observations of the photocenter variability in two AGNs, SDSS J121855+020002 and SDSS J162011+1724327 have been reported and discussed. With investigation of the variations in the quasar inner structure we explore how much this effect can affect the position determination and whether it can be (or not) detected with Gaia mission. We used (a) a model of a relativistic disk, including the perturbation that can increase brightness of a part of the disk, and consequently offset the photocenter position, and (b) a model of a dusty torus which absorbs and re-emits the incoming radiation from accretion disk. We estimated the value of the photocenter offset due to these two effects. We found that perturbations in the inner struct...

  16. The unprecedented optical outburst of the quasar 3C 454.3. The WEBT campaign of 2004-2005

    CERN Document Server

    Villata, M; Balonek, T J; Aller, M F; Jorstad, S G; Kurtanidze, O M; Nicastro, F; Nilsson, K; Aller, H D; Arai, A; Arkharov, A; Bach, U; Benítez, E; Berdyugin, A; Buemi, C S; Böttcher, M; Carosati, D; Casas, R; Caulet, A; Chen, W P; Chiang, P S; Chou, Y; Ciprini, S; Coloma, J M; Di Rico, G; Díaz, C; Efimova, N V; Forsyth, C; Frasca, A; Fuhrmann, L; Gadway, B; Gupta, S; Hagen-Thorn, V A; Harvey, J; Heidt, J; Hernandez-Toledo, H; Hroch, F; Hu, C P; Hudec, R; Ibrahimov, M A; Imada, A; Kamata, M; Kato, T; Katsuura, M; Konstantinova, T; Kopatskaya, E; Kotaka, D; Kovalev, Y Y; Kovalev, Yu A; Krichbaum, T P; Kubota, K; Kurosaki, M; Lanteri, L; Larionov, V M; Larionova, L; Laurikainen, E; Lee, C U; Leto, P; Lahteenmaki, A; López-Cruz, O; Marilli, E; Marscher, A P; McHardy, I M; Mondal, S A; Mullan, B; Napoleone, N; Nikolashvili, M G; Ohlert, J M; Postnikov, S; Pursimo, T; Ragni, M; Ros, J A; Sadakane, K; Sadun, A C; Savolainen, T; Sergeeva, E A; Sigua, L A; Sillanpää, A; Sixtova, L; Sumitomo, N; Takalo, L O; Terasranta, H; Tornikoski, M; Trigilio, C; Umana, G; Volvach, A; Voss, B; Wortel, S

    2006-01-01

    The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was R = 12.0, which represents the most luminous quasar state thus far observed (M_B ~ -31.4). In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005. The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests t...

  17. NuSTAR J033202-2746.8: Direct constraints on the Compton reflection in a heavily obscured quasar at z ≈ 2

    Energy Technology Data Exchange (ETDEWEB)

    Del Moro, A.; Mullaney, J. R.; Alexander, D. M.; Aird, J. A.; Gandhi, P. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Comastri, A.; Vignali, C.; Gilli, R. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile); Treister, E. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Civano, F. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Ranalli, P. [National Observatory of Athens, Institute of Astronomy, Astrophysics, Space Applications and Remote Sensing, Metaxa and Pavlou St., 15236 Penteli (Greece); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M. [Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Craig, W. W. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Hailey, C. J., E-mail: agnese.del-moro@durham.ac.uk [Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States); and others

    2014-05-01

    We report Nuclear Spectroscopic Telescope Array (NuSTAR) observations of NuSTAR J033202-2746.8, a heavily obscured, radio-loud quasar detected in the Extended Chandra Deep Field-South, the deepest layer of the NuSTAR extragalactic survey (∼400 ks, at its deepest). NuSTAR J033202-2746.8 is reliably detected by NuSTAR only at E > 8 keV and has a very flat spectral slope in the NuSTAR energy band (Γ=0.55{sub −0.64}{sup +0.62}; 3-30 keV). Combining the NuSTAR data with extremely deep observations by Chandra and XMM-Newton (4 Ms and 3 Ms, respectively), we constrain the broad-band X-ray spectrum of NuSTAR J033202-2746.8, indicating that this source is a heavily obscured quasar (N{sub H}=5.6{sub −0.8}{sup +0.9}×10{sup 23} cm{sup –2}) with luminosity L {sub 10-40} {sub keV} ≈ 6.4 × 10{sup 44} erg s{sup –1}. Although existing optical and near-infrared (near-IR) data, as well as follow-up spectroscopy with the Keck and VLT telescopes, failed to provide a secure redshift identification for NuSTAR J033202-2746.8, we reliably constrain the redshift z = 2.00 ± 0.04 from the X-ray spectral features (primarily from the iron K edge). The NuSTAR spectrum shows a significant reflection component (R=0.55{sub −0.37}{sup +0.44}), which was not constrained by previous analyses of Chandra and XMM-Newton data alone. The measured reflection fraction is higher than the R ∼ 0 typically observed in bright radio-loud quasars such as NuSTAR J033202-2746.8, which has L {sub 1.4} {sub GHz} ≈ 10{sup 27} W Hz{sup –1}. Constraining the spectral shape of active galactic nuclei (AGNs), including bright quasars, is very important for understanding the AGN population, and can have a strong impact on the modeling of the X-ray background. Our results show the importance of NuSTAR in investigating the broad-band spectral properties of quasars out to high redshift.

  18. Quasar Rain: Chandra and the Inner Structure of AGN

    Science.gov (United States)

    Elvis, Martin

    2014-11-01

    Chandra observations of X-ray eclipses (XRE) and Warm Absorbers (WA) in quasars produce a self-consistent view of the X-ray source and of the broad emission line region (BELR). XREs limit the size of the X-ray source and enable topographic imaging of both continuum and relativistic Fe-K. XREs imply the existence of >10(8) discrete absorbing clouds with properties consistent with being BELR clouds. These clouds are being ablated away in months and must be constantly renewed. Both eclipsing and BELR clouds have the same properties as the low ionization phase of the WAs found in LETG/HETG spectra. Hence BELR clouds must be continually condensing out of the quasar disk wind in a mist. If the clouds have not reached escape velocity they will fall toward the black hole as a quasar rain.

  19. Modeling the Structure of the Windy Torus in Quasars

    Science.gov (United States)

    Gallagher, Sarah C.; Abado, Mathew M.; Everett, John E.

    2014-07-01

    Mass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion. A convincing argument for radiation pressure driving this ionized outflow can be made within the dust sublimation radius. Beyond, radiation pressure is even more ubiquitous, as high energy photons from the central engine can now push on dust grains. This physics underlies the dusty-wind model for the putative obscuring torus. Specifically, the dusty wind in our model is first launched from the outer accretion disk as a magneto-centrifugal wind and then accelerated and shaped by radiation pressure from the central continuum. Such a wind can plausibly account for both the necessary obscuring medium to explain the observed ratio of broad-to-narrow-line quasars and the mid-infrared emission commonly seen in quasar spectral energy distributions.

  20. FAR-INFRARED PROPERTIES OF TYPE 1 QUASARS

    International Nuclear Information System (INIS)

    We use the Spitzer Space Telescope Enhanced Imaging Products and the Spitzer Archival Far-InfraRed Extragalactic Survey to study the spectral energy distributions (SEDs) of spectroscopically confirmed type 1 quasars selected from the Sloan Digital Sky Survey (SDSS). By combining the Spitzer and SDSS data with the Two Micron All Sky Survey, we are able to construct a statistically robust rest-frame 0.1-100 μm type 1 quasar template. We find that the quasar population is well-described by a single power-law SED at wavelengths less than 20 μm, in good agreement with previous work. However, at longer wavelengths, we find a significant excess in infrared luminosity above an extrapolated power-law, along with significant object-to-object dispersion in the SED. The mean excess reaches a maximum of 0.8 dex at rest-frame wavelengths near 100 μm.

  1. Smoking Quasars a New Source for Cosmic Dust

    CERN Document Server

    Elvis, M; Karovska, M; Elvis, Martin; Marengo, Massimo; Karovska, Margarita

    2002-01-01

    Although dust is widely found in astrophysics, forming dust is surprisingly difficult. The proper combination of low temperature (<2000 K) and high density is mainly found in the winds of late-type giant and supergiant stars which, as a result, are the most efficient sources of dust known. Dust ejected from these stars into the interstellar medium has multiple important effects, including obscuring background objects and enhancing star formation. We show here that quasars are also naturally copious producers of dust, if the gas clouds producing their characteristic broad lines are part of an outflowing wind. This offers an explanation for the strong link between quasars and dust, for the heavy nuclear obscuration around many quasars and introduces a new means of forming dust at early cosmological times.

  2. High-redshift quasar host galaxies with adaptive optics

    CERN Document Server

    Kuhlbrodt, B; Wisotzki, L; Jahnke, K

    2005-01-01

    We present K band adaptive optics observations of three high-redshift (z ~ 2.2) high-luminosity quasars, all of which were studied for the first time. We also bserved several point spread function (PSF) calibrators, non-simultaneously because of the small field of view. The significant temporal PSF variations on timescales of minutes inhibited a straightforward scaled PSF removal from the quasar images. Characterising the degree of PSF concentration by the radii encircling 20% and 80% of the total flux, respectively, we found that even under very different observing conditions the r20 vs. r80 relation varied coherently between individual short exposure images, delineating a well-defined relation for point sources. Placing the quasar images on this relation, we see indications that all three objects were resolved. We designed a procedure to estimate the significance of this result, and to estimate host galaxy parameters, by reproducing the statistical distribution of the individual short exposure images. We fi...

  3. Luminosity and Redshift dependence of quasar spectral properties

    Energy Technology Data Exchange (ETDEWEB)

    Daniel E. Vanden Berk et al.

    2004-03-09

    Using a large sample of quasar spectra from the SDSS, we examine the composite spectral trends of quasars as functions of both redshift and luminosity, independently of one another. Aside from the well known Baldwin effect (BE)--the decrease of line equivalent width with luminosity--the average spectral properties are remarkably similar. Host galaxy contamination and the BE are the primary causes for apparent changes in the average spectral slope of the quasars. The BE is detected for most emission lines, including the Balmer lines, but with several exceptions including NV1240A. Emission line shifts of several lines are associated with the BE. The BE is mainly a function of luminosity, but also partly a function of redshift in that line equivalent widths become stronger with redshift. Some of the complex iron features change with redshift, particularly near the small blue bump region.

  4. Microlensing in the double quasar SBS1520+530

    CERN Document Server

    Gaynullina, E R; Akhunov, T; Burkhonov, O M; Gottlöber, S; Mirtadjieva, K; Nuritdinov, S N; Tadjibaev, I; Wambsganss, J; Wisotzki, L

    2005-01-01

    We present the results of a monitoring campaign of the double quasar SBS1520+530 at Maidanak observatory from April 2003 to August 2004. We obtained light curves in V and R filters that show small-amplitude \\Delta m~0.1 mag intrinsic variations of the quasar on time scales of about 100 days. The data set is consistent with the previously determined time delay of \\Delta t=(130+-3) days by Burud et al. (2002). We find that the time delay corrected magnitude difference between the quasar images is now larger by (0.14+-0.03) mag than during the observations by Burud et al. (2002). This confirms the presence of gravitational microlensing variations in this system.

  5. The Intrinsic Quasar Luminosity Function: Accounting for Accretion Disk Anisotropy

    CERN Document Server

    DiPompeo, M A; Brotherton, M S; Runnoe, J C; Green, R F

    2014-01-01

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic --- in part due to its disk-like structure --- but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic l...

  6. Soliton fay identities: II. Bright soliton case

    International Nuclear Information System (INIS)

    We present a set of bilinear matrix identities that generalize the ones that have been used to construct the bright soliton solutions for various models. As an example of an application of these identities, we present a simple derivation of the N-bright soliton solutions for the Ablowitz–Ladik hierarchy. (paper)

  7. Spatial Brightness Perception of Trichromatic Stimuli

    Energy Technology Data Exchange (ETDEWEB)

    Royer, Michael P.; Houser, Kevin W.

    2012-11-16

    An experiment was conducted to examine the effect of tuning optical radiation on brightness perception for younger (18-25 years of age) and older (50 years of age or older) observers. Participants made forced-choice evaluations of the brightness of a full factorial of stimulus pairs selected from two groups of four metameric stimuli. The large-field stimuli were created by systematically varying either the red or the blue primary of an RGB LED mixture. The results indicate that light stimuli of equal illuminance and chromaticity do not appear equally bright to either younger or older subjects. The rank-order of brightness is not predicted by any current model of human vision or theory of brightness perception including Scotopic to Photopic or Cirtopic to Photopic ratio theory, prime color theory, correlated color temperature, V(λ)-based photometry, color quality metrics, linear brightness models, or color appearance models. Age may affect brightness perception when short-wavelength primaries are used, especially those with a peak wavelength shorter than 450 nm. The results suggest further development of metrics to predict brightness perception is warranted, and that including age as a variable in predictive models may be valuable.

  8. SURFACE PHOTOMETRY OF LOW SURFACE BRIGHTNESS GALAXIES

    NARCIS (Netherlands)

    DEBLOK, WJG; VANDERHULST, JM; BOTHUN, GD

    1995-01-01

    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies. Th

  9. Brightness and darkness as perceptual dimensions

    NARCIS (Netherlands)

    Vladusich, T.; Lucassen, M.P.; Cornelissen, F.W.

    2007-01-01

    A common-sense assumption concerning visual perception states that brightness and darkness cannot coexist at a given spatial location. One corollary of this assumption is that achromatic colors, or perceived grey shades, are contained in a one-dimensional (1-D) space varying from bright to dark. The

  10. Incoherently coupled dark-bright photorefractive solitons

    Science.gov (United States)

    Chen, Zhigang; Segev, Mordechai; Coskun, Tamer H.; Christodoulides, Demetrios N.; Kivshar, Yuri S.; Afanasjev, Vsevolod V.

    1996-11-01

    We report the observation of incoherently coupled dark-bright spatial soliton pairs in a biased bulk photorefractive crystal. When such a pair is decoupled, the dark component evolves into a triplet structure, whereas the bright one decays into a self-defocusing beam.

  11. Brightness Alteration with Interweaving Contours

    Directory of Open Access Journals (Sweden)

    Sergio Roncato

    2012-12-01

    Full Text Available Chromatic induction is observed whenever the perceived colour of a target surface shifts towards the hue of a neighbouring surface. Some vivid manifestations may be seen in a white background where thin coloured lines have been drawn (assimilation or when lines of different colours are collinear (neon effect or adjacent (watercolour to each other. This study examines a particular colour induction that manifests in concomitance with an opposite effect of colour saturation (or anti-spread. The two phenomena can be observed when a repetitive pattern is drawn in which outline thin contours intercept wider contours or surfaces, colour spreading appear to fill the surface occupied by surfaces or thick lines whereas the background traversed by thin lines is seen as brighter or filled of a saturated white. These phenomena were first observed by Bozzi (1975 and Kanizsa (1979 in figural conditions that did not allow them to document their conjunction. Here we illustrate various manifestations of this twofold phenomenon and compare its effects with the known effects of brightness and colour induction. Some conjectures on the nature of these effects are discussed.

  12. An ultra-luminous quasar at \\lowercase{$z=5.363$} with a ten billion solar mass black hole and a Meta-Rich DLA at \\lowercase{$z\\sim5$}

    CERN Document Server

    Wang, Feige; Fan, Xiaohui; Yang, Jinyi; Cai, Zheng; Yi, Weimin; Zuo, Wenwen; Wang, Ran; McGreer, Ian D; Ho, Luis C; Kim, Minjin; Yang, Qian; Bian, Fuyan; Jiang, Linhua

    2015-01-01

    We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a super-massive black hole (SMBH) with $M_{BH} = (1.07 \\pm 0.27) \\times10^{10}~M_\\odot$. With an absolute magnitude $M_{1450}=-28.92$ and bolometric luminosity $L_{bol}\\sim3.4\\times10^{14} L_{\\odot}$, J0306+1853 is one of the most luminous objects in the early Universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness and normal broad emission lines. In addition, a $z=4.986$ Damped Ly$\\alpha$ system (DLA) with $\\rm [M/H]=-1.3\\pm0.1$, among the most metal rich DLAs at $z \\gtrsim 5$, is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraint on the bright-end of quasar luminosity function and massive-end of black hole mass function. It will provide a unique laboratory to the study of BH growth and the co-evolution between BH and host galaxy with multi-wavelength follow-up observations. The future ...

  13. Environments of strong/ultrastrong, ultraviolet Fe II emitting quasars

    Science.gov (United States)

    Clowes, Roger G.; Raghunathan, Srinivasan; Söchting, Ilona K.; Graham, Matthew J.; Campusano, Luis E.

    2013-08-01

    We have investigated the strength of ultraviolet (UV) Fe II emission from quasars within the environments of large quasar groups (LQGs) in comparison with quasars elsewhere, for 1.1 ≤ zLQG ≤ 1.7, using the DR7QSO catalogue of the Sloan Digital Sky Survey. We use the Weymann et al. W2400 equivalent width, defined between the rest-frame continuum windows 2240-2255 and 2665-2695 Å, as the measure of the UV Fe II emission. We find a significant shift of the W2400 distribution to higher values for quasars within LQGs, predominantly for those LQGs with 1.1 ≤ zLQG ≤ 1.5. There is a tentative indication that the shift to higher values increases with the quasar i magnitude. We find evidence that within LQGs the ultrastrong emitters with W2400 ≥ 45 Å (more precisely, ultrastrong plus with W2400 ≥ 44 Å) have preferred nearest-neighbour separations of ˜30-50 Mpc to the adjacent quasar of any W2400 strength. No such effect is seen for the ultrastrong emitters that are not in LQGs. The possibilities for increasing the strength of the Fe II emission appear to be iron abundance, Lyα fluorescence and microturbulence, and probably all of these operate. The dense environment of the LQGs may have led to an increased rate of star formation and an enhanced abundance of iron in the nuclei of galaxies. Similarly, the dense environment may have led to more active blackholes and increased Lyα fluorescence. The preferred nearest-neighbour separation for the stronger emitters would appear to suggest a dynamical component, such as microturbulence. In one particular LQG, the Huge-LQG (the largest structure known in the early Universe), six of the seven strongest emitters very obviously form three pairings within the total of 73 members.

  14. Locating star-forming regions in quasar host galaxies

    Science.gov (United States)

    Young, J. E.; Eracleous, M.; Shemmer, O.; Netzer, H.; Gronwall, C.; Lutz, Dieter; Ciardullo, R.; Sturm, Eckhard

    2014-02-01

    We present a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope. Our observations are motivated by recent evidence for a close relationship between black hole growth and the stellar mass evolution in its host galaxy. We use narrow-band [O II]λ3727, Hβ, [O III]λ5007 and Paα images, taken with the Wide Field Planetary Camera 2 and NICMOS instruments, to map the morphology of line-emitting regions, and, after extinction corrections, diagnose the excitation mechanism and infer star-formation rates. Significant challenges in this type of work are the separation of the quasar light from the stellar continuum and the quasar-excited gas from the star-forming regions. To this end, we present a novel technique for image decomposition and subtraction of quasar light. Our primary result is the detection of extended line-emitting regions with sizes ranging from 0.5 to 5 kpc and distributed symmetrically around the nucleus, powered primarily by star formation. We determine star-formation rates of the order of a few tens of M⊙ yr-1. The host galaxies of our target quasars have stellar masses of the order of 1011 M⊙ and specific star-formation rates on a par with those of M82 and luminous infrared galaxies. As such they fall at the upper envelope or just above the star-formation mass sequence in the specific star formation versus stellar mass diagram. We see a clear trend of increasing star-formation rate with quasar luminosity, reinforcing the link between the growth of the stellar mass of the host and the black hole mass found by other authors.

  15. Unveiling the intrinsic X-ray properties of broad absorption line quasars with a relatively unbiased sample

    Energy Technology Data Exchange (ETDEWEB)

    Morabito, Leah K.; Dai, Xinyu; Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Sivakoff, Gregory R. [Department of Physics, University of Alberta, CCIS 4-183 Edmonton, AB T6G 2E1 (Canada); Shankar, Francesco [School of Physics and Astronomy, University of Southampton, Southampton SO17 IBJ (United Kingdom)

    2014-05-01

    There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at z ∼ 2, selected from a near-infrared (Two Micron All Sky Survey) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically faint (i – K{sub s} ≥ 2.3 mag) and optically bright (i – K{sub s} < 2.3 mag) samples to be Γ ≅ 1.5-2.1. We constrain their intrinsic column density by modeling the X-ray fractional hardness ratio, finding a mean column density of 3.5 × 10{sup 22} cm{sup –2} assuming neutral absorption. We incorporate Sloan Digital Sky Survey optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We estimate that the optically faint BALQSOs are X-ray weaker than the optically bright ones, and the entire sample of BALQSOs are intrinsically X-ray weak when compared to normal active galactic nuclei (AGNs). Correcting for magnification of X-ray emission via gravitational lensing by the central black hole viewed at large inclination angles makes these BALQSOs even more intrinsically X-ray weak. Finally, we estimate AGN kinetic feedback efficiencies of a few percent for an X-ray wind of 0.3c in high-ionization BALQSOs. Combined with energy carried by low-ionization BALQSOs and UV winds, the total kinetic energy in BALQSOs can be sufficient to provide AGN kinetic feedback required to explain the co-evolution between black holes and host galaxies.

  16. Formation of the Black Holes in the Highest Redshift Quasars

    OpenAIRE

    Yoo, Jaiyul; Miralda-Escude, Jordi

    2004-01-01

    The recent discovery of luminous quasars up to a redshift z=6.43 has renewed interest in the formation of black holes massive enough to power quasars. If black holes grow by Eddington-limited gas accretion with a radiative efficiency of at least 10%, the time required to grow from a stellar black hole to ~10^9 msun is ~10^9 years, close to the age of the universe at z=6. Black hole mergers may accelerate the rate of mass growth, but can also completely eject black holes from halo centers owin...

  17. Gravitational Microlensing and the Structure of Quasar Outflows

    CERN Document Server

    Chelouche, D

    2005-01-01

    We show that invaluable information on the structure of quasar outflows can be obtained by considering microlensing (ML) induced variability of absorption line troughs in lensed quasars. Depending on the structure and geometry of the outflowing gas, such extrinsic line variability can be manifested as changes to the equivalent width of the line as well as line profile distortions. Here we consider several physically distinct outflow models, having very similar spectral predictions, and show how ML induced absorption line variability can be used to distinguish between them. The merits of future systematic studies of these effects are exemplified.

  18. Microlensing of a Ring Model for Quasar Structure

    CERN Document Server

    Schild, R; Schild, Rudolph; Vakulik, Viktor

    2003-01-01

    Microlensing observations of the Q0957+561 A,B have consistently shown evidence for structure in the quasar that has not been evident in available microlensing models, where the luminous source has been consistently modeled as a single large round structure. We show that the microlensing features can easily be reproduced by a luminous quasar model motivated by observations; a luminous inner accretion disc edge and outer ring-shaped structures where the emission lines form. Such a model can explain all of the features known from 24 years of Q0957 microlensing observations.

  19. Quasars as Sources of Ultrahigh-Energy Cosmic Rays

    International Nuclear Information System (INIS)

    The results are presented that were obtained by analyzing arrival directions for cosmic rays that the Yakutsk array for studying extensive air showers recorded between 1974 and 2002 in the energy region E0 ≥5x1017 eV for zenith angles in the region θ ≤60 deg. . It is shown that quasars for which the redshift lies in the region z≤2.5 can be sources of these cosmic rays. Ordered structures are observed in the disposition of quasars and in the cosmic-ray arrival directions. These structures can be associated in one way or another with the large-scale structure of the Universe

  20. Absorption spectra of quasars and the structure of the Universe

    International Nuclear Information System (INIS)

    The analysis of the distribution of the distances between the systems of absorption lines in the quasars' spectra and the comparison of this distribution with the distribution of the distances between superclusters in the deep optical surveys are carried out. It is shown that the systems of absorption lines are connected with superclusters of galaxies. The comparison of the absorbing gas parameters with the data for coronae of the Galaxy and of the Magellanic Clouds confirms this connection and permits to revise conclusions of the theory on the properties of superclusters. The problem of unidentified absorption lines in the quasars spectra is discussed