WorldWideScience

Sample records for barred spiral galaxy

  1. Asymptotic Orbits in Barred Spiral Galaxies

    CERN Document Server

    Harsoula, Maria; Contopoulos, George

    2010-01-01

    We study the formation of the spiral structure of barred spiral galaxies, using an $N$-body model. The evolution of this $N$-body model in the adiabatic approximation maintains a strong spiral pattern for more than 10 bar rotations. We find that this longevity of the spiral arms is mainly due to the phenomenon of stickiness of chaotic orbits close to the unstable asymptotic manifolds originated from the main unstable periodic orbits, both inside and outside corotation. The stickiness along the manifolds corresponding to different energy levels supports parts of the spiral structure. The loci of the disc velocity minima (where the particles spend most of their time, in the configuration space) reveal the density maxima and therefore the main morphological structures of the system. We study the relation of these loci with those of the apocentres and pericentres at different energy levels. The diffusion of the sticky chaotic orbits outwards is slow and depends on the initial conditions and the corresponding Jaco...

  2. Orbital structure in barred spiral galaxies

    CERN Document Server

    Harsoula, Maria; 10.1111/j.1365-2966.2009.14427.x

    2010-01-01

    We study the orbital structure in a series of self-consistent $N$-body configurations simulating rotating barred galaxies with spiral and ring structures. We perform frequency analysis in order to measure the angular and the radial frequencies of the orbits at two different time snapshots during the evolution of each $N$-body system. The analysis is done separately for the regular and the chaotic orbits. We thereby identify the various types of orbits, determine the shape and percentages of the orbits supporting the bar and the ring/spiral structures, and study how the latter quantities change during the secular evolution of each system. Although the frequency maps of the chaotic orbits are scattered, we can still identify concentrations around resonances. We give the distributions of frequencies of the most important populations of orbits. We explore the phase space structure of each system using projections of the 4D surfaces of section. These are obtained via the numerical integration of the orbits of test...

  3. AGN spiral galaxies in groups: effects of bars

    OpenAIRE

    Alonso, Sol; Coldwell, Georgina; Lambas, Diego García

    2014-01-01

    We explore properties of barred active spiral galaxies in groups selected from the SDSS-DR7, with the aim of assessing the effects of bars on AGN and the role of the high density environment. We identified barred active galaxies that reside in groups from SDSS-DR7 group catalog. To provide a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distribution...

  4. AGN spiral galaxies in groups: effects of bars

    CERN Document Server

    Alonso, Sol; Lambas, Diego García

    2014-01-01

    We explore properties of barred active spiral galaxies in groups selected from the SDSS-DR7, with the aim of assessing the effects of bars on AGN and the role of the high density environment. We identified barred active galaxies that reside in groups from SDSS-DR7 group catalog. To provide a suitable quantification of the effects of bars, a reliable control sample of unbarred active galaxies in high density environments with similar redshift, magnitude, morphology, and bulge size distributions was constructed. We found that the fraction of barred AGN galaxies in groups (~ 38 %) is higher than those in the total barred AGN sample ( ~ 28 %), indicating that AGN spiral galaxies in groups are more likely to be barred than those in the field. We also found that barred AGN galaxies are more concentrated towards the group centers than the other unbarred AGN group members. In addition, barred AGN host galaxies show an excess of population dominated by red colors suggesting that bars produce an importanteffect on gala...

  5. Near-infrared surface photometry of barred spiral galaxies

    International Nuclear Information System (INIS)

    On the basis of a number of theoretical studies, it must be concluded that bar-like stellar structures are a preferred dynamical form in the process of galaxy formation and evolution. The objective of the observational research reported in this paper is to study by surface photometry parameters which describe the radial and azimuthal luminosity distributions of the bars of barred spiral galaxies. Such information is important for a comparison with theoretical models. The observational data are discussed, taking into account the photographic material, the reduction of data, and the decomposition of the radial luminosity profiles. Attention is also given to the structure of the bars, a comparison with the Miller and Smith models, and a discussion of the results. The considered study has provided near-infrared surface photometry for the stellar bars of a number of barrel spiral galaxies. 53 references

  6. The formation of spiral arms and rings in barred galaxies

    CERN Document Server

    Romero-Gomez, M; Masdemont, J J; García-Gomez, C

    2007-01-01

    In this and in a previous paper (Romero-Gomez et al. 2006) we propose a theory to explain the formation of both spirals and rings in barred galaxies using a common dynamical framework. It is based on the orbital motion driven by the unstable equilibrium points of the rotating bar potential. Thus, spirals, rings and pseudo-rings are related to the invariant manifolds associated to the periodic orbits around these equilibrium points. We examine the parameter space of three barred galaxy models and discuss the formation of the different morphological structures according to the properties of the bar model. We also study the influence of the shape of the rotation curve in the outer parts, by making families of models with rising, flat, or falling rotation curves in the outer parts. The differences between spiral and ringed structures arise from differences in the dynamical parameters of the host galaxies. The results presented here will be discussed and compared with observations in a forthcoming paper.

  7. Rings and spirals in barred galaxies. I Building blocks

    CERN Document Server

    Athanassoula, E; Masdemont, J J

    2008-01-01

    In this paper we present building blocks which can explain the formation and properties both of spirals and of inner and outer rings in barred galaxies. We first briefly summarise the main results of the full theoretical description we have given elsewhere, presenting them in a more physical way, aimed to an understanding without the requirement of extended knowledge of dynamical systems or of orbital structure. We introduce in this manner the notion of manifolds, which can be thought of as tubes guiding the orbits. The dynamics of these manifolds can govern the properties of spirals and of inner and outer rings in barred galaxies. We find that the bar strength affects how unstable the L1 and L2 Lagrangian points are, the motion within the 5A5A5Amanifold tubes and the time necessary for particles in a manifold to make a complete turn around the galactic centre. We also show that the strength of the bar, or, to be more precise, of the non-axisymmetric forcing at and somewhat beyond the corotation region, deter...

  8. Short-term dynamical evolution of grand-design spirals in barred galaxies

    CERN Document Server

    Baba, Junichi

    2015-01-01

    We investigate the short-term dynamical evolution of stellar grand-design spiral arms in barred spiral galaxies using a three-dimensional (3D) $N$-body/hydrodynamic simulation. Similar to previous numerical simulations of unbarred, multiple-arm spirals, we find that grand-design spiral arms in barred galaxies are not stationary, but rather dynamic. This means that the amplitudes, pitch angles, and rotational frequencies of the spiral arms are not constant, but change within a few hundred million years (i.e. the typical rotational period of a galaxy). We also find that the clear grand-design spirals in barred galaxies appear it only when the spirals connect with the ends of the bar. Furthermore, we find that the short-term behaviour of spiral arms in the outer regions ($R>$ 1.5--2 bar radius) can be explained by the swing amplification theory and that the effects of the bar are not negligible in the inner regions ($R<$ 1.5--2 bar radius). These results suggest that, although grand-design spiral arms in barr...

  9. Near-infrared mapping of spiral barred galaxies

    International Nuclear Information System (INIS)

    The results presented were obtained with a 32 x 32 InSb charge injection device (CID) array cooled at 4K, at the f/36 cassegrain focus of the 3m60 Canada-France-Hawaii telescope with a spatial resolution of 0.5 inches per pixel. The objects presented are spiral barred galaxies mapped at J(1.25 microns), H(1.65 microns) and K(2.2 microns). The non-axisymetric potential due to the presence of a bar induces dynamical processes leading to the confinement of matter and peculiar morphologies. Infrared imaging is used to study the link between various components. Correlations with other wavelengths ranges and 2-colors diagrams ((J-H), (H-K)) lead to the identification of star forming regions, nucleus. Maps show structures connected to the central core. The question is, are they flowing away or toward the nucleus. Observations of M83 lead to several conclusions. The star forming region, detected in the visible and the infrared cannot be very compact and must extend to the edge of the matter concentration. The general shape of the near-infrared emission and the location of radio and 10 micron peaks suggest the confinement of matter between the inner Linblad resonances localized from CO measurements about 100 and 400 pc. The distribution of color indices in the arc from southern part to the star forming region suggests an increasing amount of gas and a time evolution eventually triggered by supernova explosions. Close to the direction of the bar, a bridge-like structure connects the arc to the nucleus with peculiar color indices

  10. Effects of spiral arms on star formation in nuclear rings of barred-spiral galaxies

    International Nuclear Information System (INIS)

    We use hydrodynamic simulations to study the effect of spiral arms on the star formation rate (SFR) in nuclear rings of barred-spiral galaxies. We find that spiral arms can be an efficient means of gas transport from the outskirts to the central parts, provided that the arms are rotating slower than the bar. While the ring star formation in models with no arms or corotating arms is active only during around the bar growth phase, arm-driven gas accretion both significantly enhances and prolongs the ring star formation in models with slow-rotating arms. The arm-enhanced SFR is larger by a factor of ∼3-20 than in the no-arm model, with larger values corresponding to stronger and slower arms. Arm-induced mass inflows also make dust lanes stronger. Nuclear rings in slow-arm models are ∼45% larger than in the no-arm counterparts. Star clusters that form in a nuclear ring exhibit an age gradient in the azimuthal direction only when the SFR is small, whereas no notable age gradient is found in the radial direction for models with arm-induced star formation.

  11. Star Formation Properties in Barred Galaxies(SFB). III. Statistical Study of Bar-driven Secular Evolution using a sample of nearby barred spirals

    CERN Document Server

    Zhou, Zhi-Min; Wu, Hong

    2014-01-01

    Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend to be coincide with low concentrical star formation activity, while those with strong bars show a large scatter in the distribution of star formation activity. We find enhanced star formation activity in bulges towards stronger bars, although not predominantly, consistent with previous studies. Our results suggest that different stages of the secular process and many other factors may contribute to the complexity of the secular evolution. In addition, barred galaxies with intense star formation in bars tend to have active star formation in their bulges and disks, and bulges have higher star formation densities than bars and disks, indicating the evolutionary effects of bars. We then derived a possible criterion to quantify the ...

  12. The Frequency of Barred Spiral Galaxies in the Near-IR

    CERN Document Server

    Eskridge, P B; Pogge, R W; Quillen, A C; Davies, R L; De Poy, D L; Houdashelt, M L; Kuchinskii, L E; Ramírez, S V; Sellgren, K; Terndrup, D M; Tiede, G P; Eskridge, Paul B.; Frogel, Jay A.; Pogge, Richard W.; Quillen, Alice C.; Davies, Roger L.; Houdashelt, Mark L.; Kuchinski, Leslie E.; Ramirez, Solange V.; Terndrup, Donald M.; Tiede, Glenn P.

    1999-01-01

    We have determined the fraction of barred galaxies in the H-band for a statistically well-defined sample of 186 spirals drawn from the Ohio State University Bright Spiral Galaxy survey. We find 56% of our sample to be strongly barred at H, while another 16% is weakly barred. Only 27% of our sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of Galaxies both classify only about 30% of our sample as strongly barred. Thus strong bars are nearly twice as prevalent in the near-infrared as in the optical. The frequency of genuine optically hidden bars is significant, but lower than many claims in the literature: 40% of the galaxies in our sample that are classified as unbarred in the RC3 show evidence for a bar in the H-band, while for the Carnegie Atlas this fraction is 66%. Our data reveal no significant trend in bar fraction as a function of morphology in either the optical or H-band. Optical surveys of high redshift galaxies may be strongly biased against finding bars, as bars are increasin...

  13. Invariant manifolds as building blocks for the formation of spiral arms and rings in barred galaxies

    CERN Document Server

    Romero-Gomez, M; Masdemont, J J; García-Gomez, C

    2008-01-01

    We propose a theory to explain the formation of spiral arms and of all types of outer rings in barred galaxies, extending and applying the technique used in celestial mechanics to compute transfer orbits. Thus, our theory is based on the chaotic orbital motion driven by the invariant manifolds associated to the periodic orbits around the hyperbolic equilibrium points. In particular, spiral arms and outer rings are related to the presence of heteroclinic or homoclinic orbits. Thus, R1 rings are associated to the presence of heteroclinic orbits, while R1R2 rings are associated to the presence of homoclinic orbits. Spiral arms and R2 rings, however, appear when there exist neither heteroclinic nor homoclinic orbits. We examine the parameter space of three realistic, yet simple, barred galaxy models and discuss the formation of the different morphologies according to the properties of the galaxy model. The different morphologies arise from differences in the dynamical parameters of the galaxy.

  14. Invariant manifolds and the response of spiral arms in barred galaxies

    CERN Document Server

    Tsoutsis, P; Efthymiopoulos, C; Contopoulos, George

    2008-01-01

    The unstable invariant manifolds of the short-period family of periodic orbits around the unstable Lagrangian points $L_1$ and $L_2$ of a barred galaxy define loci in the configuration space which take the form of a trailing spiral pattern. In the present paper we investigate this association in the case of the self-consistent models of Kaufmann & Contopoulos (1996) which provide an approximation of real barred-spiral galaxies. We also examine the relation of `response' models of barred-spiral galaxies with the theory of the invariant manifolds. Our main results are the following: The invariant manifolds yield the correct form of the imposed spiral pattern provided that their calculation is done with the spiral potential term turned on. We provide a theoretical model explaining the form of the invariant manifolds that supports the spiral structure. The azimuthal displacement of the Lagrangian points with respect to the bar's major axis is a crucial parameter in this modeling. When this is taken into accou...

  15. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    Science.gov (United States)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  16. The effects of bar-spiral coupling on stellar kinematics in the Galaxy

    CERN Document Server

    Monari, Giacomo; Siebert, Arnaud; Grand, Robert J J; Kawata, Daisuke; Boily, Christian

    2016-01-01

    We investigate models of the Milky Way disc taking into account simultaneously the bar and a two-armed quasi-static spiral pattern. Away from major resonance overlaps, the mean stellar radial motions in the plane are essentially a linear superposition of the isolated effects of the bar and spirals. Thus, provided the bar is strong enough, even in the presence of spiral arms, these mean radial motions are predominantly affected by the Galactic bar for large scale velocity fluctuations. This is evident when comparing the peculiar line-of-sight velocity power spectrum of our coupled models with bar-only models. However, we show how forthcoming spectroscopic surveys could disentangle bar-only non-axisymmetric models of the Galaxy from models in which spiral arms have a significant amplitude. We also point out that overlaps of low-order resonances are sufficient to enhance stellar churning within the disc, even when the spirals amplitude is kept constant. Nevertheless, for churning to be truly non-local, stronger ...

  17. Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672

    Science.gov (United States)

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J.; Koribalski, B.; Kuntz, K. D.; Levan, A. J.; Ojha, R.; Roberts, T. P.; Ward, M. J.; Zezas, A.

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST) infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (LX 5 * 10(exp 39) erg s(exp -1)) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard (1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 * 10(exp 38) erg s(exp -1). This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  18. Star formation properties in barred galaxies. III. Statistical study of bar-driven secular evolution using a sample of nearby barred spirals

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Zhi-Min; Wu, Hong [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Cao, Chen, E-mail: zmzhou@bao.ac.cn, E-mail: hwu@bao.ac.cn, E-mail: caochen@sdu.edu.cn [School of Space Science and Physics, Shandong University at Weihai, Weihai, Shandong 264209 (China)

    2015-01-01

    Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend coincide with low concentrical star formation activity, while those with strong bars show a large scatter in the distribution of star formation activity. We find enhanced star formation activity in bulges toward stronger bars, although not predominantly, consistent with previous studies. Our results suggest that different stages of the secular process and many other factors may contribute to the complexity of the secular evolution. In addition, barred galaxies with intense star formation in bars tend to have active star formation in their bulges and disks, and bulges have higher star formation densities than bars and disks, indicating the evolutionary effects of bars. We then derived a possible criterion to quantify the different stages of the bar-driven physical process, while future work is needed because of the uncertainties.

  19. Rings and spirals in barred galaxies. III. Further comparisons and links to observations

    CERN Document Server

    Athanassoula, E; Bosma, A; Masdemont, J J

    2010-01-01

    In a series of papers, we propose a theory to explain the formation and properties of rings and spirals in barred galaxies. The building blocks of these structures are orbits guided by the manifolds emanating from the unstable Lagrangian points located near the ends of the bar. In this paper, the last of the series, we present more comparisons of our theoretical results to observations and also give new predictions for further comparisons. Our theory provides the right building blocks for the rectangular-like bar outline and for ansae. We consider how our results can be used to give estimates for the pattern speed values, as well as their effect on abundance gradients in barred galaxies. We present the kinematics along the manifold loci, to allow comparisons with the observed kinematics along the ring and spiral loci. We consider gaseous arms and their relations to stellar ones. We discuss several theoretical aspects and stress that the orbits that constitute the building blocks of the spirals and rings are c...

  20. Investigating the nuclear activity of barred spiral galaxies: the case of NGC 1672

    CERN Document Server

    Jenkins, L P; Colbert, E J M; Koribalski, B; Kuntz, K D; Levan, A J; Ojha, R; Roberts, T P; Ward, M J; Zezas, A

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST), infrared imaging from the Spitzer Space Telescope, and ATCA ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy, many of which correlate spatially with star-formation in the bar and spiral arms, while two are identified as background galaxies in the HST images. Nine of the X-ray sources are ULXs, with the three brightest (LX > 5E39 erg/s) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC1672 possesses a hard (Gamma~1.5) nuclear X-ray source with a 2-10 keV luminosity of 4E38 erg/s. This is surrounded by an X-ray bright circumnuclear star-forming ring, comprised of point sources an...

  1. Determination of resonance locations in barred spiral galaxies using multiband photometry

    CERN Document Server

    Sierra, Amber D; Treuthardt, Patrick; Puerari, Ivanio

    2015-01-01

    In this paper, we apply a method identified by Puerari & Dottori (1997) to find the corotation radii (CR) in spiral galaxies. We apply our method to 57 galaxies, 17 of which have already have their CR locations determined using other methods. The method we adopted entails taking Fourier transforms along radial cuts in the u, g, r, i, and z wavebands and comparing the phase angles as a function of radius between them. The radius at which the phase angles cross indicates the location of the corotation radius. We then calculated the relative bar pattern speed, $\\mathcal{R}$, and classified the bar as "fast", where $\\mathcal{R} < 1.4$, slow, where $\\mathcal{R} \\geq 1.4$, or intermediate, where the errors on $\\mathcal{R}$ are consistent with the bar being "slow" or "fast". For the 17 galaxies that had their CR locations previously measured, we found that our results were consistent with the values of $\\mathcal{R}$ obtained by the computer simulations of Rautiainen, Salo & Laurikainen (2008). For the lar...

  2. THE TWO-PHASE FORMATION HISTORY OF SPIRAL GALAXIES TRACED BY THE COSMIC EVOLUTION OF THE BAR FRACTION

    International Nuclear Information System (INIS)

    We study the evolution of galactic bars and the link with disk and spheroid formation in a sample of zoom-in cosmological simulations. Our simulation sample focuses on galaxies with present-day stellar masses in the 1010-1011 M☉ range, in field and loose group environments, with a broad variety of mass growth histories. In our models, bars are almost absent from the progenitors of present-day spirals at z > 1.5, and they remain rare and generally too weak to be observable down to z ≈ 1. After this characteristic epoch, the fractions of observable and strong bars rise rapidly, bars being present in 80% of spiral galaxies and easily observable in two thirds of these at z ≤ 0.5. This is quantitatively consistent with the redshift evolution of the observed bar fraction, although the latter is presently known up to z ≈ 0.8 because of band-shifting and resolution effects. Our models hence predict that the decrease in the bar fraction with increasing redshift should continue with a fraction of observable bars not larger than 10%-15% in disk galaxies at z > 1. Our models also predict later bar formation in lower-mass galaxies, in agreement with existing data. We find that the characteristic epoch of bar formation, namely redshift z ≈ 0.8-1 in the studied mass range, corresponds to the epoch at which today's spirals acquire their disk-dominated morphology. At higher redshift, disks tend to be rapidly destroyed by mergers and gravitational instabilities and rarely develop significant bars. We hence suggest that the bar formation epoch corresponds to the transition between an early 'violent' phase of spiral galaxy formation at z ≥ 1 and a late 'secular' phase at z ≤ 0.8. In the secular phase, the presence of bars substantially contributes to the growth of the (pseudo-)bulge, but the bulge mass budget remains statistically dominated by the contribution of mergers, interactions, and disk instabilities at high redshift. Early bars at z > 1 are often short

  3. GMC evolution in a barred spiral galaxy with star formation and thermal feedback

    Science.gov (United States)

    Fujimoto, Yusuke; Bryan, Greg L.; Tasker, Elizabeth J.; Habe, Asao; Simpson, Christine M.

    2016-09-01

    We explore the impact of star formation and thermal stellar feedback on the giant molecular cloud population forming in a M83-type barred spiral galaxy. We compare three high-resolution simulations (1.5 pc cell size) with different star formation/feedback models: one with no star formation, one with star formation but no feedback, and one with star formation and thermal energy injection. We analyse the resulting population of clouds, finding that we can identify the same population of massive, virialized clouds and transient, low-surface density clouds found in our previous work (that did not include star formation or feedback). Star formation and feedback can affect the mix of clouds we identify. In particular, star formation alone simply converts dense cloud gas into stars with only a small change to the cloud populations, principally resulting in a slight decrease in the transient population. Feedback, however, has a stronger impact: while it is not generally sufficient to entirely destroy the clouds, it does eject gas out of them, increasing the gas density in the intercloud region. This decreases the number of massive clouds, but substantially increases the transient cloud population. We also find that feedback tends to drive a net radial inflow of massive clouds, leading to an increase in the star formation rate in the bar region. We examine a number of possible reasons for this and conclude that it is possible that the drag force from the enhanced intercloud density could be responsible.

  4. GMC Evolution in a Barred Spiral Galaxy with Star Formation and Thermal Feedback

    CERN Document Server

    Fujimoto, Yusuke; Tasker, Elizabeth J; Habe, Asao; Simpson, Christine M

    2016-01-01

    We explore the impact of star formation and thermal stellar feedback on the giant molecular cloud (GMC) population forming in a M83-type barred spiral galaxy. We compare three high-resolution simulations (1.5 pc cell size) with different star formation/feedback models: one with no star formation, one with star formation but no feedback, and one with star formation and thermal energy injection. We analyze the resulting population of clouds, finding that we can identify the same population of massive, virialized clouds and transient, low-surface density clouds found in our previous work (that did not include star formation or feedback). Star formation and feedback can affect the mix of clouds we identify. In particular, star formation alone simply converts dense cloud gas into stars with only a small change to the cloud populations, principally resulting in a slight decrease in the transient population. Feedback, however, has a stronger impact: while it is not generally sufficient to entirely destroy the clouds...

  5. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  6. BARS DO DRIVE SPIRAL DENSITY WAVES

    International Nuclear Information System (INIS)

    Recently, Buta et al. examined the question 'Do Bars Drive Spiral Density Waves?', an idea supported by theoretical studies and also from a preliminary observational analysis. They estimated maximum bar strengths Qb , maximum spiral strengths Qs , and maximum m = 2 arm contrasts A 2s for 23 galaxies with deep Anglo-Australian Telescope (AAT) Ks -band images. These were combined with previously published Qb and Qs values for 147 galaxies from the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) sample and with the 12 galaxies from Block et al. Weak correlation between Qb and Qs was confirmed for the combined sample, whereas the AAT subset alone showed no significant correlations between Qb and Qs , nor between Qb and A 2s. A similar negative result was obtained in Durbala et al. for 46 galaxies. Based on these studies, the answer to the above question remains uncertain. Here we use a novel approach, and show that although the correlation between the maximum bar and spiral parameters is weak, these parameters do correlate when compared locally. For the OSUBSGS sample, a statistically significant correlation is found between the local spiral amplitude, and the forcing due to the bar's potential at the same distance, out to ∼1.6 bar radii (the typical bar perturbation is then of the order of a few percent). Also for the sample of 23 AAT galaxies of Buta et al., we find a significant correlation between local parameters out to ∼1.4 bar radii. Our new results confirm that, at least in a statistical sense, bars do indeed drive spiral density waves.

  7. Do Bars Drive Spiral Density Waves?

    CERN Document Server

    Buta, R J; Elmegreen, B G; Salo, H; Laurikainen, E; Elmegreen, D M; Puerari, I; Block, D L

    2009-01-01

    We present deep near-infrared K_s-band AAT IRIS2 observations of a selected sample of nearby barred spiral galaxies, including some with the strongest known bars. The sample covers a range of Hubble types from SB0- to SBc. The goal is to determine if the torque strengths of the spirals correlate with those of the bars, which might be expected if the bars actually drive the spirals as has been predicted by theoretical studies. This issue has implications for interpreting bar and spiral fractions at high redshift. Analysis of previous samples suggested that such a correlation exists in the near-infrared, where effects of extinction and star formation are less important. However, the earlier samples had only a few excessively strong bars. Our new sample largely confirms our previous studies, but still any correlation is relatively weak. We find two galaxies, NGC 7513 and UGC 10862, where there is a only a weak spiral in the presence of a very strong bar. We suggest that some spirals probably are driven by their ...

  8. Bar-driven evolution and quenching of spiral galaxies in cosmological simulations

    CERN Document Server

    Spinoso, Daniele; Dotti, Massimo; Mayer, Lucio; Madau, Piero; Bellovary, Jillian

    2016-01-01

    We analyse the output of the hi-res cosmological zoom-in simulation ErisBH to study self-consistently the formation of a strong stellar bar in a Milky Way-type galaxy and its effect on the galactic structure, on the central gas distribution and on star formation. The simulation includes radiative cooling, star formation, SN feedback and a central massive black hole which is undergoing gas accretion and is heating the surroundings via thermal AGN feedback. A large central region in the ErisBH disk becomes bar-unstable after z~1.4, but a clear bar-like structure starts to grow significantly only after z~0.4, possibly triggered by the interaction with a massive satellite. At z~0.1 the bar reaches its maximum radial extent of l~2.2 kpc. As the bar grows, it becomes prone to buckling instability, which we quantify based on the anisotropy of the stellar velocity dispersion. The actual buckling event is observable at z~0.1, resulting in the formation of a boxy-peanut bulge clearly discernible in the edge-on view of ...

  9. Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy

    Science.gov (United States)

    Beaton, R. L.; Athanassoula, E.; Majewski, S. R.; Guhathakurta, P.; Skrutskie, M. F.; Patterson, R. J.; Bureau, M.

    2005-12-01

    For the past 50 years a number of studies have suggested that the center of M31 may be barred. These optical studies, however, have been hampered by the highly inclined (i=77.5o) disk of M31 and the obscuring effects of its embedded dust, which strongly influence the observed isophotal structure of the M31 center. We analyze a new near-infrared survey of M31 by the Two Micron All Sky Survey (2MASS) 6X program. These data, covering the full extent of the optical disk, present a view of the central structure of M31 almost completely unfettered by dust. This new portrait vividly reveals a central bulge dominating the near infrared light profile from 3 to 1000 arcsecs along the semi-major axis, and with a number of interesting properties: (1) prominent boxy isophotes across the extent of the bulge, (2) a position angle inclined by about 10o from that of the M31 disk, (3) strong isophotal twisting in the innermost regions of the bulge, and (4) the presence of ansae symmetrically extending beyond the bulge along the position angle of the galaxy disk. In other highly inclined disks such properties have been associated with the presence of central bars obscured by projection effects. In the case of M31, these features have been well reproduced in a fully self consistent N-body simulation of a barred galaxy with a boxy bulge. The models further suggest the existence of an additional classical bulge component at the center of M31, and imply that the bar itself extends beyond the observationally established extent of the boxy bulge. This publication makes use of data products from 2MASS, which is a joint project of U Mass and IPAC/CalTech, funded by NASA and the NSF. This work was supported by NSF grants AST-0307842 and AST-0307966, as well as a SIM Key Project grant, NASA/JPL contract 1228235. MFS acknowledges support from NASA/JPL contract 1234021. This work was also partially supported by the Celerity Foundation. EA thanks the INSU/CNRS, the Région PACA and the University

  10. The VIRUS-P Exploration of Nearby Spiral Galaxies (VENGA): Spatially Resolved Gas-Phase Metallicity Distributions in Barred and Unbarred Spirals

    CERN Document Server

    Kaplan, Kyle F; Kewley, Lisa; Blanc, Guillermo A; Weinzirl, Tim; Song, Mimi; Drory, Niv; Luo, Rongxin; Bosch, Remco C E van den

    2016-01-01

    We present a study of the excitation conditions and metallicity of ionized gas ($Z_{\\rm gas}$) in eight nearby barred and unbarred spiral galaxies from the VIRUS-P Exploration of Nearby Galaxies (VENGA) survey, which provides high spatial sampling and resolution (median $\\sim$ 387 pc), large coverage from the bulge to outer disc, broad wavelength range (3600-6800 \\AA{}), and medium spectral resolution ($\\sim$ 120 km s$^{-1}$ at 5000 \\AA{}). Our results are: (1) We present high resolution gas excitation maps to differentiate between regions with excitation typical of Seyfert, LINER, or recent star formation. We find LINER-type excitation at large distances (3-10 kpc) from the centre, and associate this excitation with diffuse ionized gas (DIG). (2) After excluding spaxels dominated by Seyfert, LINER, or DIG, we produce maps with the best spatial resolution and sampling to date of the ionization parameter $q$, star formation rate, and $Z_{\\rm gas}$ using common strong line diagnostics. We find that isolated bar...

  11. Effect of bars on the galaxy properties

    CERN Document Server

    Vera, Matias; Coldwell, Georgina

    2016-01-01

    Aims: With the aim of assessing the effects of bars on disc galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong, weak and without bars. Method: We identified barred galaxies from the Sloan Digital Sky Survey. By visual inspection, we classified the face-on spiral galaxies brighter than g<16.5 mag into strong-bar, weak-bar and unbarred. In order to provide an appropiate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshift, magnitude, morphology, bulge sizes, and local density environment distributions to that of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies, representing a 25.82% of the full sample of spiral galaxies, in good agreement with previous studies. We also found that strong-barred galaxies show less efficient star formation activity and older stellar populations compared to weak-barred and unbarred spirals from the c...

  12. Bars do drive spiral density waves

    CERN Document Server

    Salo, H; Buta, R; Knapen, J H

    2010-01-01

    Recently, Buta etal. (2009) examined the question "Do Bars Drive Spiral Density Waves?", an idea supported by theoretical studies and also from a preliminary observational analysis Block etal (2004). They estimated maximum bar strengths Q_b, maximum spiral strengths Q_s, and maximum m=2 arm contrasts A_2s for 23 galaxies with deep AAT K_s-band images. These were combined with previously published Q_b and Q_s values for 147 galaxies from the OSUBSGS sample and with the 12 galaxies from Block etal(2004). Weak correlation between Q_b and Q_s was confirmed for the combined sample, whereas the AAT subset alone showed no significant correlations between Q_b and Q_s, nor between Q_b and A_2s. A similar negative result was obtained in Durbala etal. (2009) for 46 galaxies. Based on these studies, the answer to the above question remains uncertain. Here we use a novel approach, and show that although the correlation between the maximum bar and spiral parameters is weak, these parameters do correlate when compared local...

  13. Are spiral galaxies heavy smokers?

    International Nuclear Information System (INIS)

    The dustiness of spiral galaxies is discussed. Starburst galaxies and the shortage of truly bright spiral galaxies is cited as evidence that spiral galaxies are far dustier than has been thought. The possibility is considered that the dust may be hiding missing mass

  14. Gas flow in barred potentials II. Bar Driven Spiral Arms

    CERN Document Server

    Sormani, Mattia C; Magorrian, John

    2015-01-01

    Spiral arms that emerge from the ends of a galactic bar are important in interpreting observations of our and external galaxies. It is therefore important to understand the physical mechanism that causes them. We find that these spiral arms can be understood as kinematic density waves generated by librations around underlying ballistic closed orbits. This is even true in the case of a strong bar, provided the librations are around the appropriate closed orbits and not around the circular orbits that form the basis of the epicycle approximation. An important consequence is that it is a potential's orbital structure that determines whether a bar should be classified as weak or strong, and not crude estimates of the potential's deviation from axisymmetry.

  15. Backwards Spiral Galaxy

    Science.gov (United States)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected. A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus. The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State Community College in Alabama

  16. CO Multi-line Imaging of Nearby Galaxies (COMING): I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903

    CERN Document Server

    Muraoka, Kazuyuki; Kuno, Nario; Nakai, Naomasa; Nakanishi, Hiroyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Miyamoto, Yusuke; Kishida, Nozomi; Hatakeyama, Takuya; Umei, Michiko; Tanaka, Takahiro; Tomiyasu, Yuto; Saita, Chey; Ueno, Saeko; Matsumoto, Naoko; Salak, Dragan; Morokuma, Kana

    2016-01-01

    We present simultaneous mappings of J=1-0 emission of 12CO, 13CO, and C18O molecules toward the whole disk (8' x 5' or 20.8 kpc x 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45-m telescope at an effective angular resolution of 20" (or 870 pc). We detected 12CO(J=1-0) emission over the disk of NGC 2903. In addition, significant 13CO(J=1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C18O(J=1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of 12CO(J=2-1)/12CO(J=1-0) ($R_{2-1/1-0}$) and 13CO(J=1-0)/12CO(J=1-0) ($R_{13/12}$), we performed the stacking analysis for our 12CO(J=1-0), 13CO(J=1-0), and archival 12CO(J=2-1) spectra with velocity-axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged $R_{2-1/1-0}$ and $R_{13/12}$ with high significance for all the regions...

  17. Galaxy Zoo: Passive Red Spirals

    CERN Document Server

    Masters, Karen L; Romer, A Kathy; Nichol, Robert C; Bamford, Steven P; Schawinski, Kevin; Lintott, Chris J; Andreescu, Dan; Campbell, Heather C; Crowcroft, Ben; Doyle, Isabelle; Edmondson, Edward M; Murray, Phil; Raddick, M Jordan; Slosar, Anze; Szalay, Alexander S; Vandenberg, Jan

    2009-01-01

    We study the spectroscopic properties and environments of red spiral galaxies found by the Galaxy Zoo project. By carefully selecting face-on, disk dominated spirals we construct a sample of truly passive disks (not dust reddened, nor dominated by old stellar populations in a bulge). As such, our red spirals represent an interesting set of possible transition objects between normal blue spirals and red early types. We use SDSS data to investigate the physical processes which could have turned these objects red without disturbing their morphology. Red spirals prefer intermediate density regimes, however there are no obvious correlations between red spiral properties and environment - environment alone is not sufficient to determine if a galaxy will become a red spiral. Red spirals are a small fraction of spirals at low masses, but dominate at large stellar masses - massive galaxies are red independent of morphology. We confirm that red spirals have older stellar populations and less recent star formation than ...

  18. Rotation Curves of Spiral Galaxies

    CERN Document Server

    Sofue, Y; SOFUE, Yoshiaki; RUBIN, Vera

    2000-01-01

    Rotation curves of spiral galaxies are the major tool for determining the distribution of mass in spiral galaxies. They provide fundamental information for understanding the dynamics, evolution and formation of spiral galaxies. We describe various methods to derive rotation curves, and review the results obtained. We discuss the basic characteristics of observed rotation curves in relation to various galaxy properties, such as Hubble type, structure, activity, and environment.

  19. Morphologies introduced by bistability in barred-spiral galactic potentials

    Science.gov (United States)

    Tsigaridi, L.; Patsis, P. A.

    2015-04-01

    We investigate the orbital dynamics of a barred-spiral model when the system is rotating slowly and corotation is located beyond the end of the spiral arms. In the characteristic of the central family of periodic orbits, we find a `bistable region'. In the response model, we observe a ring surrounding the bar and spiral arms starting tangential to the ring. This is a morphology resembling barred-spiral systems with inner rings. However, the dynamics associated with this structure in the case we study is different from that of a typical bar ending close to corotation. The ring of our model is round, or rather elongated perpendicular to the bar. It is associated with a folding (an `S'-shaped feature) of the characteristic of the central family, which is typical in bistable bifurcations. Along the `S' part of the characteristic, we have a change in the orientation of the periodic orbits from an x1-type to an x2-type morphology. The orbits populated in the response model change rather abruptly their orientation when reaching the lowest energy of the `S'. The spirals of the model follow a standard `precessing ellipses flow' and the orbits building them have energies beyond the `S' region. The bar is structured mainly by sticky orbits from regions around the stability islands of the central family. This leads to the appearance of X features in the bars on the galactic plane. Such a bar morphology appears in the unsharp-masked images of some moderately inclined galaxies.

  20. Global extinction in spiral galaxies

    NARCIS (Netherlands)

    Tully, RB; Pierce, MJ; Saunders, W; Verheijen, MAW; Witchalls, PL

    1998-01-01

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces Clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in the B, R, I, and K' bands. Extinction causes systematic scatter in color-magnit

  1. Gas dynamics in barred spirals, II: NGC 7496 and 289

    International Nuclear Information System (INIS)

    The gas velocity fields in the barred spiral galaxies NGC 7496 and 289 have been measured by means of long-slit spectra obtained with the Anglo-Australian Telescope. Pronounced deviations from circular motion of the type predicted by recent theoretical models are seen in NGC 7496: the isovelocity contours are distorted into a characteristic S-shaped pattern and there is a large velocity gradient across the bar. The velocity field is virtually identical to that of a previously observed barred spiral, NGC 5383 for which a number of models have been published. The nuclear [OIII] emission lines are very asymmetric with a wing extending to about 1000 km s-1 to the blue of the systemic velocity; this wing is only faintly seen in the Balmer lines. NGC 289 has a much smaller bar and consequently the noncircular motions are less pronounced. The most obvious effect is that the kinematic major and minor axes are not perpendicular which is a signature of oval distortions. As a further test of the models of gas streaming in barred spirals the results from 11 previously studied galaxies have been collected. It is shown that the appearance of the velocity field depends on the orientation of the bar to the line of sight, in good agreement with the model predictions

  2. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    Science.gov (United States)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

  3. 棒对星系核区恒星形成活动的影响%The Effect of Bar on Nuclear Star-forming Activities in Nearby Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    汪潋

    2009-01-01

    利用SDSS光谱,研究了IRAS卫星亮红外源星表中的盘状星系中的恒星形成性质,并着重探讨了棒对星系核区恒星形成活动的影响.利用星族合成的方法得到了每个样本星系核区的恒星组成性质、恒星形成活动的强度等信息,并比较了星系整体和核区恒星形成性质的差异.得到的结论:除去相互作用,样本中的棒星系显示出比非棒旋星系更强的核区恒星形成活动和更多的年轻星族成分.%By using SDSS spectra, we have studied nuclear star-forming properties of nearby spiral galaxies selected from Infrared Revised Bright Galaxy Sample, and try to find the effect of bar structure on star-forming activities in the nuclear regions of nearby galaxies. The composition of stellar population and the strength of star formation activities in the sample galaxies are acquired by using stellar population synthesis code ?STARLIGHT, and the star formation properties in nuclear regions are compared with that of the whole galaxies. We find that the star formation in barred spiral galaxies is more intensive than non-barred ones and barred spirals show much younger stellar populations.

  4. Quantitative analysis of spirality in elliptical galaxies

    CERN Document Server

    Dojcsak, Levente

    2013-01-01

    We use an automated galaxy morphology analysis method to quantitatively measure the spirality of galaxies classified manually as elliptical. The data set used for the analysis consists of 60,518 galaxy images with redshift obtained by the Sloan Digital Sky Survey (SDSS) and classified manually by Galaxy Zoo, as well as the RC3 and NA10 catalogues. We measure the spirality of the galaxies by using the Ganalyzer method, which transforms the galaxy image to its radial intensity plot to detect galaxy spirality that is in many cases difficult to notice by manual observation of the raw galaxy image. Experimental results using manually classified elliptical and S0 galaxies with redshift <0.3 suggest that galaxies classified manually as elliptical and S0 exhibit a nonzero signal for the spirality. These results suggest that the human eye observing the raw galaxy image might not always be the most effective way of detecting spirality and curves in the arms of galaxies.

  5. Dynamical Evolution of Barred Galaxies

    OpenAIRE

    Athanassoula, E

    2005-01-01

    Angular momentum redistribution within barred galaxies drives their dynamical evolution. Angular momentum is emitted mainly by near-resonant material in the bar region and absorbed by resonant material mainly in the outer disc and in the halo. This exchange determines the strength of the bar, the decrease of its pattern speed, as well as its morphology. If the galaxy has also a gaseous component and/or a companion or satellite, then these also take part in the angular momentum exchange. Durin...

  6. The Spiral Galaxy M33

    CERN Document Server

    Hodge, P

    2012-01-01

    This book summarizes the gathering of information on and the growing understanding of M33 from the 1920s, when Hubble first determined its true nature, to the 21st century, when the Hubble Telescope probed deeply into its many secrets. With its regular symmetrical spiral structure, and its being not tilted too much and near enough to allow detailed studies of its stars, M33 is well-suited for the study of a typical spiral galaxy. In this work, Paul Hodge places current research on M33 (and similar galaxies) in both historical and global perspectives. The book is written in a language accessible for specialists and non-specialists, for professional and amateur astronomers, for scientists and the curious public and, most importantly, for students.  

  7. Global Extinction in Spiral Galaxies

    CERN Document Server

    Tully, R B; Huang, J S; Saunders, W J; Verheijen, M A W; Witchalls, P L

    1998-01-01

    Magnitude-limited samples of spiral galaxies drawn from the Ursa Major and Pisces clusters are used to determine their extinction properties as a function of inclination. Imaging photometry is available for 87 spirals in B,R,I and K' bands. Extinction causes systematic scatter in color-magnitude plots. A strong luminosity dependence is found. Relative edge-on to face-on extinction of up to 1.7 mag is found at B for the most luminous galaxies but is unmeasurably small for faint galaxies. At R the differential absorption with inclination reaches 1.3 mag, at I it reaches 1.0 mag, and at K' the differential absorption can in the extreme be as great as 0.3 mag. The luminosity dependence of reddening can be translated into a dependence on rotation rate which is a distance-independent observable. Hence, corrections can be made that are useful for distance measurements. The strong dependence of the corrections on luminosity act to steepen luminosity-linewidth correlations. The effect is greatest toward the blue, with...

  8. Tidally-Induced Offset Disks in Magellanic Spiral Galaxies

    CERN Document Server

    Pardy, Stephen A; Athanassoula, E; Wilcots, Eric M; Sheth, Kartik

    2016-01-01

    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar, and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyrs, the time that it takes for the disk to be re-centered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, thes...

  9. On Three-Dimensional Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    LUO Xin-Lian; PENG Qiu-He; LONG Min; PENG Fang; ZOU Zhi-Gang

    2000-01-01

    Density waves in 3D spiral galaxies are studied. In order to eliminate the forbidden region near the corotation in the grand-design galaxies, we assume that the perturbation satisfies the stable condition Q(r) > 1 over all the disk except that at the corotation. Then, a new method is put forward here to determine some basic parameters of spiral galaxies. We apply it to our Galaxy, and the results are in good agreement with the previous results.

  10. Hydrodynamical Simulations of Nuclear Rings in Barred Galaxies

    OpenAIRE

    Li, Zhi; Shen, Juntai; Kim, Woong-Tae

    2015-01-01

    Dust lanes, nuclear rings, and nuclear spirals are typical gas structures in the inner region of barred galaxies. Their shapes and properties are linked to the physical parameters of the host galaxy. We use high-resolution hydrodynamical simulations to study 2D gas flows in simple barred galaxy models. The nuclear rings formed in our simulations can be divided into two groups: one group is nearly round and the other is highly elongated. We find that roundish rings may not form when the bar pa...

  11. Bar Formation from Galaxy Flybys

    CERN Document Server

    Lang, Meagan; Sinha, Manodeep

    2014-01-01

    Recently, both simulations and observations have revealed that flybys - fast, one-time interactions between two galaxy halos - are surprisingly common, nearing/comparable to galaxy mergers. Since these are rapid, transient events with the closest approach well outside the galaxy disk, it is unclear if flybys can transform the galaxy in a lasting way. We conduct collisionless N-body simulations of three co-planer flyby interactions between pure-disk galaxies to take a first look at the effects flybys have on disk structure, with particular focus on stellar bar formation. We find that some flybys are capable of inciting a bar with bars forming in both galaxies during our 1:1 interaction and in the secondary during our 10:1 interaction. The bars formed have ellipticities >0.5, sizes on the order of the host disk's scale length, and persist to the end of our simulations, ~5 Gyr after pericenter. The ability of flybys to incite bar formation implies that many processes associated with secular bar evolution may be ...

  12. Fourier Dissection of Early-Type Galaxy Bars

    CERN Document Server

    Buta, R; Salo, H; Block, D L; Knapen, J H

    2006-01-01

    This paper reports on a near-infrared survey of early-type galaxies designed to provide information on bar strengths, bulges, disks, and bar parameters in a statistically well-defined sample of S0-Sa galaxies. Early-type galaxies have the advantage that their bars are relatively free of the effects of dust, star formation, and spiral structure that complicate bar studies in later type galaxies. We describe the survey and present results on detailed analysis of the relative Fourier intensity amplitudes of bars in 26 early-type galaxies. We also evaluate the symmetry assumption of these amplitudes with radius, used recently for bar-spiral separation in later-type galaxies. The results show a wide variety of radial Fourier profiles of bars, ranging from simple symmetric profiles that can be represented in terms of a single gaussian component, to both symmetric and asymmetric profiles that can be represented by two overlapping gaussian components. More complicated profiles than these are also found, often due to ...

  13. Dynamical Evolution of Barred Galaxies

    CERN Document Server

    Athanassoula, E

    2005-01-01

    Angular momentum redistribution within barred galaxies drives their dynamical evolution. Angular momentum is emitted mainly by near-resonant material in the bar region and absorbed by resonant material mainly in the outer disc and in the halo. This exchange determines the strength of the bar, the decrease of its pattern speed, as well as its morphology. If the galaxy has also a gaseous component and/or a companion or satellite, then these also take part in the angular momentum exchange. During the evolution a bar structure forms in the inner parts of the halo as well. This bar is shorter and fatter than the disc bar and stays so all through the simulation, although its length grows considerably with time. Viewed edge-on, the bar in the disc component acquires a boxy or peanut shape. I describe the families of periodic orbits that explain such structures and review the observations showing that boxy/peanut `bulges' are in fact just bars seen edge-on.

  14. Characterizing Barred Galaxies in the Abell 901/902 Supercluster

    CERN Document Server

    Marinova, I; Bacon, D; Balogh, M; Barden, M; Barazza, F D; Bell, E F; Böhm, A; Caldwell, J A R; Gray, M E; Haussler, B; Heymans, C; Jahnke, K; Van Kampen, E; Koposov, S; Lane, K; McIntosh, D H; Meisenheimer, K; Peng, C Y; Rix, H -W; Sánchez, S F; Taylor, A; Wisotzki, L; Wolf, C; Zheng, X

    2008-01-01

    In dense clusters, higher densities at early epochs as well as physical processes, such as ram pressure stripping and tidal interactions become important, and can have direct consequences for the evolution of bars and their host disks. To study bars and disks as a function of environment, we are using the STAGES ACS HST survey of the Abell 901/902 supercluster (z~0.165), along with earlier field studies based the SDSS and the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS). We explore the limitations of traditional methods for characterizing the bar fraction, and in particular highlight uncertainties in disk galaxy selection in cluster environments. We present an alternative approach for exploring the proportion of bars, and investigate the properties of bars as a function of host galaxy color, Sersic index, stellar mass, star formation rate (SFR), specific SFR, and morphology.

  15. Bar instabilities in Coma cluster galaxies

    International Nuclear Information System (INIS)

    The radial distribution of bar versus nonbar galaxies within the Coma cluster shows that a significantly larger fraction of bar galaxies are members of the cluster core. This result can be used either to estimate the time scale for the decay of bar instabilities or to argue that galaxies in the core of Coma are confined within the core

  16. Magnetic fields and halos in spiral galaxies

    OpenAIRE

    Krause, Marita

    2014-01-01

    Radio continuum observations allow to reveal the magnetic field structure in the disk and halo of nearby spiral galaxies, their magnetic field strength and vertical scale heights. The spiral galaxies studied so far show a similar magnetic field pattern which is of spiral shape along the disk plane and X-shaped in the halo, sometimes accompanied by strong vertical fields above and below the central region of the disk. The strength of the halo field is comparable to that of the disk. The total ...

  17. A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar

    CERN Document Server

    Emsellem, E; Ferruit, P; Emsellem, Eric; Goudfrooij, Paul; Ferruit, Pierre

    2003-01-01

    TIGER integral-field spectrography and HST/WFPC2 imaging of the E3 galaxy NGC 2974 are used to derive the kinematics of the stellar and ionized gas components in its central 500 pc. We derive a numerical two-integral distribution function from a MGE mass model using the HQ formalism. The TIGER as well as published long-slit stellar kinematics are well fitted with this self-consistent model, requiring neither the addition of a significant mass contribution from a hidden disc structure, nor the presence of a central dark mass. The data reveal the presence of a striking, highly contrasted, two-arm gaseous spiral structure within a radius of ~200 pc, corresponding to a total mass of 6.8x10^4 Msun of ionized gas. We use a deconvolved TIGER datacube to probe its kinematics at a resolution of about 0.35 arcsec. Strong departures from circular motions are observed, as well as high velocity dispersion values on the inner side of the arms. We interpret the observed gas morphology and kinematics as the signature of stre...

  18. Star formation in isolated AMIGA galaxies: dynamical influence of bars

    CERN Document Server

    Verley, S; Verdes-Montenegro, L; Bergond, G; Leon, S

    2007-01-01

    Star formation depends strongly both on the local environment of galaxies, and on the internal dynamics of the interstellar medium. To disentangle the two effects, we obtained, in the framework of the AMIGA project, Ha and Gunn r photometric data for more than 200 spiral galaxies lying in very low-density regions of the local Universe. We characterise the Ha emission, tracing current star formation, of the 45 largest and less inclined galaxies observed for which we estimate the torques between the gas and the bulk of the optical matter. We could subsequently study the Ha morphological aspect of these isolated spiral galaxies. Using Fourier analysis, we focus on the modes of the spiral arms and also on the strength of the bars, computing the torques between the gas and newly formed stars (Ha) and the bulk of the optical matter (Gunn r). We interpret the various bar/spiral morphologies observed in terms of the secular evolution experienced by galaxies in isolation. We also classify the different spatial distrib...

  19. Radial Mixing due to Spiral-Bar Resonance Overlap: Implications to the Milky Way

    CERN Document Server

    Minchev, I

    2010-01-01

    We have recently identified a previously unknown radial migration mechanism resulting from the overlap of spiral and bar resonances in galactic discs (Minchev & Famaey 2010, Minchev et al. 2010). This new mechanism is much more efficient than mixing by transient spirals and its presence is unavoidable in all barred galaxies, such as our own Milky Way. The consequences of this are a strong flattening in the metallicity gradient in the disc, an extended disc profile, and the formation of a thick disc component, all taking place in only a couple of Gyr. This timescale is drastically shorter than previously expected and thus can put strong constraints on the longevity, strength and pattern speeds of the Galactic bar and Spiral Structure.

  20. Galaxy Zoo: Observing Secular Evolution Through Bars

    CERN Document Server

    Cheung, Edmond; Masters, Karen L; Nichol, Robert C; Bosma, A; Bell, Eric F; Faber, S M; Koo, David C; Lintott, Chris; Melvin, Thomas; Schawinski, Kevin; Skibba, Ramin A; Willett, Kyle W

    2013-01-01

    Observations have shown that there is a connection between the presence of a bar and the properties of a galaxy. In a parallel effort, simulations have shown that this connection is consistent with the theory of bar-driven secular evolution. But observational evidence of bar-driven secular evolution has been sparse. In this paper, we use the Galaxy Zoo 2 dataset to look for evidence of this secular evolution. Our sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 +/- 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role of bars in disk galaxy evolution. We characterize bars by the bar likelihood, the likelihood a bar is present in a given galaxy, and the bar length. These two bar properties show interesting correlations with the specific star formation rate and the inner central structure of galaxies. Comparing these observations to state-of-the-art simulations of bar evolution, which include live halos and ...

  1. Spiral Galaxy Lensing: A Model with Twist

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Steven R.; Ernst, Brett; Fancher, Sean [Purdue University (United States); Keeton, Charles R. [Rutgers University, Department of Physics and Astronomy (United States); Komanduru, Abi; Lundberg, Erik, E-mail: elundberg9@gmail.com [Purdue University (United States)

    2014-12-15

    We propose a single galaxy gravitational lensing model with a mass density that has a spiral structure. Namely, we extend the arcsine gravitational lens (a truncated singular isothermal elliptical model), adding an additional parameter that controls the amount of spiraling in the structure of the mass density. An important feature of our model is that, even though the mass density is sophisticated, we succeed in integrating the deflection term in closed form using a Gauss hypergeometric function. When the spiraling parameter is set to zero, this reduces to the arcsine lens.

  2. NGC 2442 Tidal Encounters and the Evolution of Spiral Galaxies

    CERN Document Server

    Mihos, C; Mihos, Chris; Bothun, Greg

    1997-01-01

    Using imaging Fabry-Perot data, we study the star-forming properties and kinematics of the nearby barred spiral galaxy NGC 2442. The Halpha emission is very localized along the strong spiral arms of the galaxy, and shows a marked asymmetry between the sharp, well-defined northern tidal arm and the weaker southern arm. The velocity field appears highly distorted, with a rapidly rotating nuclear component. We find evidence for strong non-circular motions along the northern arm, coincident with the pronounced dust lane and regions of intense star formation. The strong asymmetries, disturbed velocity field, and presence of a perturbed companion suggest that we are witnessing a strong kinematic response to a close interaction, which has redistributed the star formation activity throughout the disk of NGC 2442. Dynamical modeling supports this hypothesis, and suggests that the regions of strongest star formation are coincident with strong shocks occurring along the perturbed northern arm. Despite this redistributio...

  3. Molecular gas distribution in spiral galaxies

    International Nuclear Information System (INIS)

    One of the major factors influencing both the morphology and evolution of spiral galaxies is the abundance and distribution of dense interstellar matter. Young stars formed from the gas clouds are responsible for the appearance and perhaps even the maintenance of the spiral pattern. Since these stars also generate a disproportionate share of the galactic luminosity, the long term evolution of galaxies is directly related to the exhaustion of this matter (i.e., its absorption into low mass stars). The ability to probe all three gas components (molecular, atomic, and ionic) in addition to the luminosity from the young stars is a unique capability of the far infrared. (Auth.)

  4. Spiral structure in galaxies: analogies

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, R.C.

    1976-01-01

    The vortex analogy to galactic spiral structures is considered. Caution against carrying the analogy past its region of applicability is noted; and some experiments with vorticities are mentioned. (JFP)

  5. Galaxy Zoo: Observing secular evolution through bars

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, Edmond; Faber, S. M.; Koo, David C. [Department of Astronomy and Astrophysics, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States); Athanassoula, E.; Bosma, A. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Masters, Karen L.; Nichol, Robert C.; Melvin, Thomas [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Lintott, Chris [Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Skibba, Ramin A. [Center for Astrophysics and Space Sciences, Department of Physics, 9500 Gilman Drive, University of California, San Diego, CA 92093 (United States); Willett, Kyle W., E-mail: ec2250@gmail.com [School of Physics and Astronomy, University of Minnesota, MN 55455 (United States)

    2013-12-20

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  6. Galaxy Zoo: Observing secular evolution through bars

    International Nuclear Information System (INIS)

    In this paper, we use the Galaxy Zoo 2 data set to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR) and bulge prominence. Our sample consists of 13,295 disk galaxies, with an overall (strong) bar fraction of 23.6% ± 0.4%, of which 1154 barred galaxies also have bar length (BL) measurements. These samples are the largest ever used to study the role of bars in galaxy evolution. We find that the likelihood of a galaxy hosting a bar is anticorrelated with SSFR, regardless of stellar mass or bulge prominence. We find that the trends of bar likelihood and BL with bulge prominence are bimodal with SSFR. We interpret these observations using state-of-the-art simulations of bar evolution that include live halos and the effects of gas and star formation. We suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks, a factor demonstrated to significantly retard both bar formation and evolution in models. We interpret the bimodal relationship between bulge prominence and bar properties as being due to the complicated effects of classical bulges and central mass concentrations on bar evolution and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

  7. Galaxy Zoo: Observing Secular Evolution Through Bars

    Science.gov (United States)

    Cheung, Edmond; Athanassoula, L.; Masters, K.; Faber, S. M.; Koo, D. C.; Zoo, Galaxy

    2014-01-01

    In this talk, I use the Galaxy Zoo 2 dataset to study the behavior of bars in disk galaxies as a function of specific star formation rate (SSFR), and inner galactic structure, i.e., the prominence of the bulge as parameterized by Sérsic index and central surface stellar mass density. Our sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 ± 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role of bars in disk galaxy evolution. I find that the likelihood of a galaxy hosting a bar is anti-correlated with SSFR, regardless of stellar mass or bulge prominence. I find that the trends of bar likelihood with bulge prominence are bimodal with SSFR, i.e., in star-forming galaxies, bulges are more prominent in galaxies more likely to host bars, while in quiescent disk galaxies, bars are less frequent where there are prominent bulges. Our observations of bar length reveal a complex picture. In star-forming disks, longer bars are found where the bulges are more prominent, while in quiescent disks there is a maximum in the average bar length as a function of bulge prominence. I interpret these observations using state-of-the-art simulations of bar evolution which include live halos and the effects of gas and star formation. I suggest our observed trends of bar likelihood with SSFR are driven by the gas fraction of the disks; a factor demonstrated to significantly retard both bar formation and evolution in models. I interpret the bimodal relationship between bulge prominence and bar properties as due to the complicated effects of classical bulges and central mass concentrations on bar evolution, and also to the growth of disky pseudobulges by bar evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies, but are a critical evolutionary driver of their

  8. The surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    It is proposed that Freeman's discovery that the extrapolated central surface brightness of spiral galaxies is approximately constant can be simply explained if the galaxies contain a spheroidal component which dominates the light in their outer isophotes. Calculations of an effective central surface brightness indicate a wide spread of values. This requires either a wide spread in disc properties or significant spheroidal components or, most probably, both. (author)

  9. Dark and visible matter in spiral galaxies

    International Nuclear Information System (INIS)

    Exploiting relevant information from the profiles of rotation curves, we calculate the dark-to-luminous mass ratio within the disc size for a sample of 43 spiral galaxies. The values we find, while proving the ubiquitous presence of dark matter, vary with luminosity. Faint and bright galaxies are found to be respectively halo- and disc-dominated in the disc regions. The luminosity sequence turns out to be a dark-to-luminous sequence. (author)

  10. Galaxy Zoo: CANDELS Barred Disks and Bar Fractions

    CERN Document Server

    Simmons, B D; Lintott, Chris; Masters, Karen L; Willett, Kyle W; Keel, William C; Smethurst, R J; Cheung, Edmond; Nichol, Robert C; Schawinski, Kevin; Rutkowski, Michael; Kartaltepe, Jeyhan S; Bell, Eric F; Casteels, Kevin R V; Conselice, Christopher J; Almaini, Omar; Ferguson, Henry C; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M; McIntosh, Daniel H; Mortlock, Alice; Newman, Jeffrey A; Ownsworth, Jamie; Bamford, Steven; Dahlen, Tomas; Faber, Sandra M; Finkelstein, Steven L; Fontana, Adriano; Galametz, Audrey; Grogin, N A; Grutzbauch, Ruth; Guo, Yicheng; Haussler, Boris; Jek, Kian J; Kaviraj, Sugata; Lucas, Ray A; Peth, Michael; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

    2014-01-01

    The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1.5 in deep rest-frame optical images from CANDELS. From within a sample of 876 disk galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a sub-sample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5< z < 2 (f_bar = 10.7 +6.3 -3.5% after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disk galaxies have evolved over the last 11 bil...

  11. Dense Cloud Formation and Star Formation in a Barred Galaxy

    CERN Document Server

    Nimori, M; Sorai, K; Watanabe, Y; Hirota, A; Namekata, D

    2012-01-01

    We investigate the properties of massive, dense clouds formed in a barred galaxy and their possible relation to star formation, performing a two-dimensional hydrodynamical simulation with the gravitational potential obtained from the 2Mass data from the barred spiral galaxy, M83. Since the environment for cloud formation and evolution in the bar region is expected to be different from that in the spiral arm region, barred galaxies are a good target to study the environmental effects on cloud formation and the subsequent star formation. Our simulation uses for an initial 80 Myr an isothermal flow of non-self gravitating gas in the barred potential, then including radiative cooling, heating and self-gravitation of the gas for the next 40 Myr, during which dense clumps are formed. We identify many cold, dense gas clumps for which the mass is more than $10^4M_{\\odot}$ (a value corresponding to the molecular clouds) and study the physical properties of these clumps. The relation of the velocity dispersion of the i...

  12. Dependence of Barred Galaxy Fraction on Galaxy Properties and Environment

    CERN Document Server

    Lee, Gwang-Ho; Lee, Myung Gyoon; Choi, Yun-Young

    2011-01-01

    We investigate the dependence of occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than $M_{r}=-19.5+5$log$h$ at $0.02\\le z\\le0.05489$, drawn from the SDSS DR 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio $b/a>0.60$, we find 3,240 barred galaxies ($f_{bar}=30.4%$) which divide into 2,542 strong bars ($f_{SB1}=23.8%$) and 698 weak bars ($f_{SB2}=6.5%$). We find that $f_{SB1}$ increases as $u-r$ color becomes redder, and that it has a maximum value at intermediate velocity dispersion ($\\sigma\\simeq$150 km s$^{-1}$). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with $\\sigma>150$ km s${}^{-1}$. We also find that $f_{bar}$ ...

  13. Damping of the Milky Way bar by manifold-driven spirals

    CERN Document Server

    Lokas, Ewa L

    2016-01-01

    We describe a new phenomenon of `bar damping' that may have played an important role in shaping the Milky Way bar and bulge as well as its spiral structure. We use a collisionless N-body simulation of a Milky Way-like galaxy initially composed of a dark matter halo and an exponential disk with Toomre parameter slightly above unity. In this configuration, dominated by the disk in the center, a bar forms relatively quickly, after 1 Gyr of evolution. This is immediately followed by the formation of two manifold-driven spiral arms and the outflow of stars that modifies the potential in the vicinity of the bar, apparently shifting the position of the L_1/L_2 Lagrange points. This modification leads to the shortening of the bar and the creation of a next generation of manifold-driven spiral arms at a smaller radius. The process repeats itself a few times over the next 0.5 Gyr resulting in further substantial weakening and shortening of the bar. The time when the damping comes to an end coincides with the first buck...

  14. Stellar Kinematic Constraints on Galactic Structure Models Revisited: Bar and Spiral Arm Resonances

    CERN Document Server

    Antoja, T; Pichardo, B; Moreno, E; Figueras, F; Fernández, D

    2009-01-01

    We study the phase space available to the local stellar distribution using a Galactic potential consistent with several recent observational constraints. We find that the induced phase space structure has several observable consequences. The spiral arm contribution to the kinematic structure in the solar neighborhood may be as important as the one produced by the Galactic bar. We suggest that some of the stellar kinematic groups in the solar neighborhood, like the Hercules structure and the kinematic branches, can be created by the dynamical resonances of self-gravitating spiral arms and not exclusively by the Galactic bar. A structure coincident with the Arcturus kinematic group is developed when a hot stellar disk population is considered, which introduces a new perspective on the interpretation of its extragalactic origin. A bar-related resonant mechanism can modify this kinematic structure.We show that particles in the dark matter disk-like structure predicted by recent LCDM galaxy formation experiments, ...

  15. CUMULATIVE OXYGEN ABUNDANCES OF SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Studying the global evolution of spiral galaxies requires determining their overall chemical compositions. However, since spirals tend to possess gradients in their chemical compositions, determining their overall chemical abundances poses a challenge. In this study, the framework for a newly proposed method for determining the overall oxygen abundance of a disk is established. By separately integrating the absolute amounts of hydrogen and oxygen out to large radii, the cumulative oxygen abundance is shown to approach an asymptotic value. In this manner, a reliable account of the overall chemical state of a disk is revealed.

  16. Hot gas in Mach cones around Virgo Cluster spiral galaxies

    OpenAIRE

    Wezgowiec, M.; Vollmer, B.; Ehle, M.; Dettmar, R. -J.; Bomans, D. J.; Chyzy, K. T.; Urbanik, M.; Soida, M.

    2011-01-01

    The detailed comparison between observations and simulations of ram pressure stripped spiral galaxies in the Virgo cluster has led to a three dimensional view of the galaxy orbits within the hot intracluster medium. The 3D velocities and Mach numbers derived from simulations can be used to derive simple Mach cone geometries for Virgo spiral galaxies. We search for indications of hot gas within Mach cones in X-ray observations of selected Virgo Cluster spiral galaxies (NGC 4569, NGC 4388, and ...

  17. Near-Infrared Imaging of Barred Halo Dominated Low Surface Brightness Galaxies

    OpenAIRE

    Honey, M.; Das, M.; Ninan, J. P.; Purvankara, M.

    2016-01-01

    We present a near-infrared (NIR) imaging study of barred low surface brightness (LSB) galaxies using the TIFR near-infrared Spectrometer and Imager (TIRSPEC). LSB galaxies are dark matter dominated, late type spirals that have low luminosity stellar disks but large neutral hydrogen (HI) gas disks. Using SDSS images of a very large sample of LSB galaxies derived from the literature, we found that the barred fraction is only 8.3%. We imaged twenty five barred LSB galaxies in the J, H, K$_S$ wav...

  18. Exploring spiral galaxy potentials with hydrodynamical simulations

    CERN Document Server

    Slyz, A D; Rix, H W; Slyz, Adrianne; Kranz, Thilo; Rix, Hans-Walter

    2003-01-01

    We study how well the complex gas velocity fields induced by massive spiral arms are modelled by the hydrodynamical simulations we used to constrain the dark matter fraction in nearby spiral galaxies (Kranz et al. 2001, 2003). More specifically, we explore the dependence of the positions and amplitudes of features in the gas flow on the temperature of the interstellar medium (assumed to behave as a one-component isothermal fluid), the non-axisymmetric disk contribution to the galactic potential, the pattern speed, Omega_p, and finally the numerical resolution of the simulation. We argue that, after constraining the pattern speed reasonably well by matching the simulations to the observed spiral arm morphology, the amplitude of the non-axisymmetric perturbation (the disk fraction) is left as the primary parameter determining the gas dynamics. However, due to the sensitivity of the positions of the shocks to modeling parameters, one has to be cautious when quantitatively comparing the simulations to observation...

  19. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Rubin, Vera C. [Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Józsa, Gyula I. G.; Struve, Christian [ASTRON (Netherlands Organisation for Scientific Research NWO), Oude Hoogeveensedijk 4, 7991-PD Dwingeloo (Netherlands)

    2013-10-01

    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  20. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    We examined star formation in two very luminous (MV = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies

  1. The relationship of galaxy morphology to nuclear star formation in non-interacting spiral galaxies

    International Nuclear Information System (INIS)

    Three specific questions concerning the relationship between galactic morphology and infrared properties were addressed for noninteracting galaxies: (1) the scarcity of high infrared luminosity Sa galaxies compared to Sb and Sc; (2) the relationship between the bulge to total luminosity and the infrared properties of early type spirals; and (3) nuclear star formation processes in noninteracting galaxies. These questions were answered using IRAS data, CO (1 to 0) measurements, 2 micron, 10 micron, and visible CCD observations. Only four percent of Sa's in the Revised Shapley-Ames Catalog (RSAC) with B(gamma) is less than 12 have infrared luminosities 1/6th of the ratio for Sb's and Sc's. Less than three Sa's of 166 in the RSAC have nuclear starbursts not associated with interactions or active nuclei. A comparison of neutral hydrogen fluxes and CO fluxes with infrared fluxes implies that molecular cloud formation is inhibited in Sa's, leading to the lack of infrared activity. An investigation of the role of bulges in suppressing star formation in Sa through Sb spirals relied on the photometric observations of Kent, Kodaira, and Cornell and on IRAS infrared observatories. The results indicate that disk star formation is relatively unaffected by bulge size. The hypothesis that high far-infrared luminosities in noninteracting galaxies are dependent on material fed into the nuclei by bars was tested by near infrared imaging of a sample of 15 optically unbarred galaxies in a search for hidden bars. At least 8 of these galaxies do not appear to have bars. Strong bars therefore are not an absolute requirement for high infrared luminosity

  2. Star Formation in Two Luminous Spiral Galaxies

    CERN Document Server

    Hunter, Deidre A; Rubin, Vera C; Ashburn, Allison; Wright, Teresa; Jozsa, Gyula I G; Struve, Christian

    2013-01-01

    We have examined star formation in two very luminous (M_V=-22 to -23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Halpha images. We combine these with UBV and 2MASS JHK images and HI maps to explore the star formation characteristics of disk galaxies at high luminosity. Halpha traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Halpha further out is likely due to loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to form spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over 3-orders of magnitude and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gra...

  3. A Photometrically and Spectroscopically Confirmed Population of Passive Spiral Galaxies

    CERN Document Server

    Fraser-McKelvie, Amelia; Pimbblet, Kevin A; Dolley, Tim; Crossett, Jacob P; Bonne, Nicolas J

    2016-01-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z<0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph (WiFeS) to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000\\AA\\ breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and IFU spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  4. Modeling the Mass Distribution in Spiral Galaxies

    CERN Document Server

    Broeils, A H; Broeils, Adrick H.; Courteau, Stephane

    1996-01-01

    We use deep r-band photometry and Halpha rotation curves for a sample of 290 late-type spirals to model their mass distribution within the optical radius. We examine luminosity profile decompositions into bulge and disk carefully and confirm that bulge light is best modeled by a seeing-convolved exponential profile. The optical rotation curves are well-reproduced with a combination of bulge and "maximum" disk components only. No dark halo is needed. The disk mass-to-light ratios (M/L's) correlate with the "size" of galaxies, as measured by mass, luminosity, or disk scale length. Correcting for this scale effect yields a narrow distribution of intrinsic M/L's for this galaxy population. By combining these models with HI data for other samples, we confirm that the luminous mass fraction increases with galaxy "size".

  5. Hydrodynamical Simulations of Nuclear Rings in Barred Galaxies

    Science.gov (United States)

    Li, Zhi; Shen, Juntai; Kim, Woong-Tae

    2015-08-01

    Dust lanes, nuclear rings, and nuclear spirals are typical gas structures in the inner region of barred galaxies. Their shapes and properties are linked to the physical parameters of the host galaxy. We use high-resolution hydrodynamical simulations to study 2D gas flows in simple barred galaxy models. The nuclear rings formed in our simulations can be divided into two groups: one group is nearly round and the other is highly elongated. We find that roundish rings may not form when the bar pattern speed is too high or the bulge central density is too low. We also study the periodic orbits in our galaxy models, and find that the concept of inner Lindblad resonance (ILR) may be generalized by the extent of x2 orbits. All roundish nuclear rings in our simulations settle in the range of x2 orbits (or ILRs). However, knowing the resonances is insufficient to pin down the exact location of these nuclear rings. We suggest that the backbone of round nuclear rings is the x2 orbital family, i.e. round nuclear rings are allowed only in the radial range of x2 orbits. A round nuclear ring forms exactly at the radius where the residual angular momentum of infalling gas balances the centrifugal force, which can be described by a parameter f_ring measured from the rotation curve. We find an empirical relation between the bar parameters and f_ring, and apply it to measure bar pattern speed in a sample of barred galaxies with nuclear rings.

  6. Tidally Induced Bars of Galaxies in Clusters

    Science.gov (United States)

    Łokas, Ewa L.; Ebrová, Ivana; del Pino, Andrés; Sybilska, Agnieszka; Athanassoula, E.; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-08-01

    Using N-body simulations, we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and a Navarro-Frenk-White dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case, we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger and longer, and have lower pattern speeds for tighter orbits. Only for the tightest orbit are the properties of the bar controlled by the orientation of the tidal torque from the cluster at pericenter. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All of the bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when the tidal forces are stronger. Using all simulation outputs of galaxies at different evolutionary stages, we construct a toy model of the galaxy population in the cluster and measure the average bar strength and bar fraction as a function of clustercentric radius. Both are found to be mildly decreasing functions of radius. We conclude that tidal forces can trigger bar formation in cluster cores, but not in the outskirts, and thus can cause larger concentrations of barred galaxies toward the cluster center.

  7. A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy NGC 2974: signature of an inner bar

    OpenAIRE

    Emsellem, Eric; Goudfrooij, Paul; Ferruit, Pierre

    2003-01-01

    TIGER integral-field spectrography and HST/WFPC2 imaging of the E3 galaxy NGC 2974 are used to derive the kinematics of the stellar and ionized gas components in its central 500 pc. We derive a numerical two-integral distribution function from a MGE mass model using the HQ formalism. The TIGER as well as published long-slit stellar kinematics are well fitted with this self-consistent model, requiring neither the addition of a significant mass contribution from a hidden disc structure, nor the...

  8. Effect of bars in AGN host galaxies and black hole activity

    OpenAIRE

    Alonso, Sol; Coldwell, Georgina; Lambas, Diego Garcia

    2012-01-01

    With the aim of assessing the effects of bars on active galactic nuclei (AGN), we present an analysis of host characteristics and nuclear activity of AGN galaxies with and without bars selected from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). By visual inspection of SDSS images we classified the hosts of face-on AGN spiral galaxies brighter than g < 16.5 into barred or unbarred. With the purpose of providing an appropriate quantification of the effects of bars, we also constructed...

  9. Internal Extinction in Spiral Galaxies. Inclination Dependence

    Science.gov (United States)

    Magris, G. C.; Bruzual, G. A.

    1987-05-01

    . Kent (1986) finds that the surface brightness profiles (r) of spiral galaxies have a weak dependence, if any, on the inclination e with respect to the line of sight. This author also finds a correlation between the MIL ratio and the inclination of a galaxy. The lack of dependence of (r) in , = cos 8 indicates that the disk of these galaxies is optically thick ( .>l), due to the presence of dust grains. For an optically thick system o(r) a + 2.5 log . The cosecant law : 1.086 (Holmberg, 1975) does not explain the observed behaviour of a(r) with . 8ru'ual, Magris and Calvet (1986) solved the radiative transfer equation for a mixture of stars and dispersive dust grains distributed homogeneously in a plane parallel configuration, taking into account the wavelenght dependence of the albedo and , as well as the redistribution in angle of photons scattered by dust grains. The transfer equation is solved for the dimensionless intensity ?( , ) I( , )/I*, where 1* is the intensity emerging from the dust free configuration. The solution, CA -2.5 log (r..=0, ) , includes the correction to the galaxy magnitude due to the excess number 0+ stellar sources along the line o+ sigth (cc -i) with respect to the =I case (face on galaxy). For optically thick systems, does not depend on . The luminosity of a disk galaxy observed with inclination ,q 1 given in our model by L cc , from which log(M/L) = const + (.4 8.N( )'. with G.N . ) = -2.5 log( ). The constant is determined from the mass- luminosity. ratio of a dust free system. In terms of the correction (3(N) we can explain Kent's observations with values of between .3 and 4. These values are consistent with the observation of . -independent surface brightness profiles mentioned above. From this analysis we conclude that the correction terms of Bruzual, Magris and Calvet (1986), which take into account the dispersive properties of interstellar dust, can explain the behaviour of ar) and MIL with galaxy inclination. These correction

  10. Internal kinematics of spiral galaxies in distant rich galaxy clusters

    CERN Document Server

    Jäger, K; Ziegler, B L; Heidt, J; Moellenhoff, C

    2004-01-01

    We present our project on galaxy evolution in the environment of distant rich clusters aiming at disentangling the importance of specific interaction and galaxy transformation processes from the hierarchical evolution of field galaxies. Spatially resolved MOS spectra were gained with VLT/FORS to analyze the internal kinematics of disk galaxies. First results are shown for the clusters MS 1008.1-1224 (z=0.30), Cl 0303+1706 (z=0.42), and Cl 0413-6559 (z=0.51). Out of 35 late type cluster members, 13 galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part. The other members have peculiar kinematics. The 13 cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field with corresponding redshifts. The same is true for seven non-cluster galaxies observed in the cluster fields. The TF-cluster spirals do not show any significant luminosity evolutio...

  11. Dwarf spheroidal galaxy kinematics and spiral galaxy scaling laws

    OpenAIRE

    Salucci, Paolo; Wilkinson, Mark I.; Walker, Matthew G.; Gilmore, Gerard F.; Grebel, Eva K.; Koch, Andreas; Martins, Christiane Frigerio; Wyse, Rosemary F. G.

    2011-01-01

    Kinematic surveys of the dwarf spheroidal (dSph) satellites of the Milky Way are revealing tantalising hints about the structure of dark matter (DM) haloes at the low-mass end of the galaxy luminosity function. At the bright end, modelling of spiral galaxies has shown that their rotation curves are consistent with the hypothesis of a Universal Rotation Curve whose shape is supported by a cored dark matter halo. In this paper, we investigate whether the internal kinematics of the Milky Way dSp...

  12. Slowly rotating bars-Morphologies introduced by bistability in barred-spiral galactic potentials

    CERN Document Server

    Tsigaridi, L

    2015-01-01

    We investigate the orbital dynamics of a \\textit{barred-spiral} model when the system is rotating slowly and corotation is located beyond the end of the spiral arms. In the characteristic of the central family of periodic orbits we find a "bistable region". In the response model we observe a ring surrounding the bar and spiral arms starting tangential to the ring. This is a morphology resembling barred-spiral systems with inner rings. However, the dynamics associated with this structure in the case we study is different from that of a typical bar ending close to corotation. The ring of our model is round, or rather elongated perpendicular to the bar. It is associated with a folding (an "S" shaped feature) of the characteristic of the central family, which is typical in bistable bifurcations. Along the "S" part of the characteristic we have a change in the orientation of the periodic orbits from a x1-type to a x2-type morphology. The orbits populated in the response model change rather abruptly their orientati...

  13. Hydrodynamical Simulations of Nuclear Rings in Barred Galaxies

    CERN Document Server

    Li, Zhi; Kim, Woong-Tae

    2015-01-01

    Dust lanes, nuclear rings, and nuclear spirals are typical gas structures in the inner region of barred galaxies Their shapes and properties are linked to the physical parameters of the host galaxy. We use high-resolution hydrodynamical simulations to study 2D gas flows in simple barred galaxy models. The nuclear rings formed in our simulations can be divided into two groups: one group is nearly round and the other is highly elongated. We find that roundish rings may not form when the bar pattern speed is too high or the bulge central density is too low. We also study the periodic orbits in our galaxy models, and find that the concept of inner Lindblad resonance (ILR) may be generalized by the extent of $x_2$ orbits. All roundish nuclear rings in our simulations settle in the range of $x_2$ orbits (or ILRs). However, knowing the resonances is insufficient to pin down the exact location of these nuclear rings. We suggest that the backbone of round nuclear rings is the $x_2$ orbital family, i.e. round nuclear r...

  14. Star formation and the surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    The (blue) surface brightness of spiral galaxies is significantly correlated with their Hα linewidth. This can be most plausibly interpreted as a correlation of surface brightness with star formation rate. There is also a significant difference in surface brightness between galaxies forming stars in a grand design spiral pattern and those with floc star formation regions. (author)

  15. Effect of bars in AGN host galaxies and black hole activity

    CERN Document Server

    Alonso, Sol; Lambas, Diego Garcia

    2012-01-01

    With the aim of assessing the effects of bars on active galactic nuclei (AGN), we present an analysis of host characteristics and nuclear activity of AGN galaxies with and without bars selected from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). By visual inspection of SDSS images we classified the hosts of face-on AGN spiral galaxies brighter than g < 16.5 into barred or unbarred. With the purpose of providing an appropriate quantification of the effects of bars, we also constructed a suitable control sample of unbarred AGN galaxies with similar redshift, magnitude, morphology, bulge sizes and local environment distributions. We find that the bar fraction, with respect to the full sample of spiral face-on AGN host galaxies, is 28.5%, in good agreement with previous works. Barred AGN host galaxies show an excess of young stellar populations dominated by red u-r and g-r colors, with respect to the control sample, suggesting that bars produce an important effect on galaxy properties of AGN hosts. Re...

  16. The role of bars in AGN fueling in disk galaxies over the last seven billion years

    CERN Document Server

    Cisternas, Mauricio; Salvato, Mara; Knapen, Johan H; Civano, Francesca; Santini, Paola

    2014-01-01

    We present empirical constraints on the influence of stellar bars on the fueling of active galactic nuclei (AGN) out to z=0.84 using a sample of X-ray-selected AGN hosted in luminous face-on disk galaxies from the Chandra COSMOS survey. Using high-resolution Hubble Space Telescope imaging to identify bars, we find that the fraction of barred active galaxies displays a similar behavior as that of inactive spirals, declining with redshift from 71% at z~0.3, to 35% at z~0.8. With active galaxies being typically massive, we compare them against a mass-matched sample of inactive spirals and find that the AGN bar fraction is higher, with this enhancement being marginal at z>0.4, but becoming more pronounced at low redshift. The presence of a bar has no influence on the AGN strength, with barred and unbarred active galaxies showing equivalent X-ray luminosity distributions, though barred galaxies on average seem to show higher levels of central star formation. From our results, we conclude that the role of bars is r...

  17. Chemical evolution in spiral and irregular galaxies

    Science.gov (United States)

    Torres-Peimbert, S.

    1986-01-01

    A brief review of models of chemical evolution of the interstellar medium in our galaxy and other galaxies is presented. These models predict the time variation and radial dependence of chemical composition in the gas as function of the input parameters; initial mass function, stellar birth rate, chemical composition of mass lost by stars during their evolution (yields), and the existence of large scale mass flows, like infall from the halo, outflow to the intergalactic medium or radial flows within a galaxy. At present there is a considerable wealth of observational data on the composition of HII regions in spiral and irregular galaxies to constrain the models. Comparisons are made between theory and the observed physical conditions. In particular, studies of helium, carbon, nitrogen and oxygen abundances are reviewed. In many molecular clouds the information we have on the amount of H2 is derived from the observed CO column density, and a standard CO/H2 ratio derived for the solar neighborhood. Chemical evolution models and the observed variations in O/H and N/O values, point out the need to include these results in a CO/H2 relation that should be, at least, a function of the O/H ratio. This aspect is also discussed.

  18. Barred Galaxies in the Coma Cluster

    CERN Document Server

    Marinova, Irina; Trentham, Neil; Ferguson, Henry C; Weinzirl, Tim; Balcells, Marc; Carter, David; Brok, Mark den; Erwin, Peter; Graham, Alister W; Goudfrooij, Paul; Guzman, Rafael; Hammer, Derek; Hoyos, Carlos; Peletier, Reynier F; Huxor, Avon P; Peng, Erik; Kleijn, Gijs Verdoes

    2010-01-01

    We use ACS data from the HST Treasury survey of the Coma cluster (z~0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ~470 cluster members brighter than M_I = -11 mag, we select a sample of 46 disk galaxies (S0--Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47+/-11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (a_bar > 2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ~2 in the very high-density environment of the rich Coma cluster core.

  19. 12CO(3-2) Emission in Spiral Galaxies: Warm Molecular Gas in Action?

    CERN Document Server

    Galaz, Gaspar; Bronfman, Leonardo; Rubio, Monica

    2008-01-01

    Using the APEX sub-millimeter telescope we have investigated the 12CO(3-2) emission in five face-on nearby barred spiral galaxies, where three of them are high surface brightness galaxies (HSBs) lying at the Freeman limit, and two are low surface brightness galaxies (LSBs). We have positive detections for two of three HSB spirals and non-detections for the LSBs. For the galaxies with positive detection (NGC0521 and PGC070519), the emission is confined to their bulges, with velocity dispersions of ~90 and ~73 km/s and integrated intensities of 1.20 and 0.76 K/km/s, respectively. For the non-detections, the estimated upper limit for the integrated intensity is ~0.54 K/km/s. With these figures we estimate the H2 masses as well as the atomic-to-molecular mass ratios. Although all the galaxies are barred, we observe 12CO(3-2) emission only for galaxies with prominent bars. We speculate that bars could dynamically favor the 12CO(3-2) emission, as a second parameter after surface brightness. Therefore, secular evolu...

  20. Observational effects of explosions in the nuclei of spiral galaxies

    International Nuclear Information System (INIS)

    We conclude that an explosive event will produce a distinct observational signature evidenced by an inner ringlike structure of the principal spiral tracers, conspicuous dips in the gas rotation curve at the locus of this ring, and a ringlike or double radio structure in the plane of the galaxy. Evidence is presented supporting the suggestion that one particular spiral galaxy, NGC 4736, exhibits this characteristic signature and therefore is a galaxy which may have undergone a recent explosive event in its nucleus

  1. Evolutionary synthesis models for spirals and irregular galaxies

    OpenAIRE

    Mollá, Mercedes

    2007-01-01

    We show autoconsistent chemical and spectro-photometric evolution models applied to spiral and irregular galaxies. Evolutionary synthesis models usually used to explain the stellar component spectro-photometric data, are combined with chemical evolution models, to determine precisely the evolutionary history of spiral and irregular galaxies. In this piece of work we will show the results obtained for a wide grid of modeled theoretical galaxies

  2. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    OpenAIRE

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A.

    2011-01-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and ve...

  3. Near-Infrared Imaging of Barred Halo Dominated Low Surface Brightness Galaxies

    CERN Document Server

    Honey, M; Ninan, J P; Purvankara, M

    2016-01-01

    We present a near-infrared (NIR) imaging study of barred low surface brightness (LSB) galaxies using the TIFR near-infrared Spectrometer and Imager (TIRSPEC). LSB galaxies are dark matter dominated, late type spirals that have low luminosity stellar disks but large neutral hydrogen (HI) gas disks. Using SDSS images of a very large sample of LSB galaxies derived from the literature, we found that the barred fraction is only 8.3%. We imaged twenty five barred LSB galaxies in the J, H, K$_S$ wavebands and twenty nine in the K$_S$ band. Most of the bars are much brighter than their stellar disks, which appear to be very diffuse. Our image analysis gives deprojected mean bar sizes of $R_{b}/R_{25}$ = 0.40 and ellipticities $e$ $\\approx$ 0.45, which are similar to bars in high surface brightness galaxies. Thus, although bars are rare in LSB galaxies, they appear to be just as strong as bars found in normal galaxies. There is no correlation of $R_{b}/R_{25}$ or $e$ with the relative HI or stellar masses of the galax...

  4. Tidally induced bars of galaxies in clusters

    CERN Document Server

    Lokas, Ewa L; del Pino, Andres; Sybilska, Agnieszka; Athanassoula, E; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-01-01

    Using N-body simulations we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and an NFW dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger, longer and have lower pattern speeds for tighter orbits. Only for the tightest orbit the properties of the bar are controlled by the orientation of the tidal torque from the cluster at pericenters. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when th...

  5. Scale Heights of Non-Edge-on Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    Tao Hu; Qiu-He Peng; Ying-He Zhao

    2006-01-01

    We present a method of calculating the scale height of non-edge-on spiral galaxies, together with a formula for errors. The method is based on solving Poisson's equation for a logarithmic disturbance of matter density in spiral galaxies. We show that the spiral arms can not extend to inside the "forbidden radius" γ0, due to the effect of the finite thickness of the disk. The method is tested by re-calculating the scale heights of 71 northern spiral galaxies previously calculated by Ma, Peng & Gu.Our results differ from theirs by less than 9%. We also present the scale heights of a further 23 non-edge-on spiral galaxies.

  6. Orientation of spiral galaxies in the local supercluster

    International Nuclear Information System (INIS)

    Two alternative models for the spatial orientation of galaxies - parallelism and perpendicularity of the planes of galaxies with respect to the supergalactic plane - are compared with the observed orientations of spiral galaxies within the volume of the radius of 50 Mpc. The first model does not agree with experimental data whereas the second one-perpendicularity of the planes - describes the above data well

  7. On galaxy spiral arms' nature as revealed by rotation frequencies

    NARCIS (Netherlands)

    Roca-Fabrega, Santi; Valenzuela, Octavio; Figueras, Francesca; Romero-Gomez, Merce; Velazquez, Hector; Antoja Castelltort, Teresa; Pichardo, Barbara

    2013-01-01

    High-resolution N-body simulations using different codes and initial condition techniques reveal two different behaviours for the rotation frequency of transient spiral arms like structures. Whereas unbarred discs present spiral arms nearly corotating with disc particles, strong barred models (bulge

  8. Self-Perpetuating Spiral Arms in Disk Galaxies

    CERN Document Server

    D'Onghia, Elena; Hernquist, Lars

    2012-01-01

    The precise nature of spiral structure in galaxies remains uncertain. Recent studies suggest that spiral arms result from interactions between disks and satellite galaxies. Instead, leaving aside the grand bisymmetric spirals, here we consider the possibility that the multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can survive at least in a statistical sense long after the original perturbing influence has been removed. Our findings thus motivate a ...

  9. The Discovery of Spiral Arms in the Starburst Galaxy M82

    CERN Document Server

    Mayya, Y D; Luna, A

    2005-01-01

    We report the discovery of two symmetric spiral arms in the near-infrared (NIR) images of the starburst galaxy M82. The spiral arms are recovered when an axi-symmetric exponential disk is subtracted from the NIR images. The arms emerge from the ends of the NIR bar and can be traced up to three disk scalelengths. The winding of the arms is consistent with an m=2 logarithmic spiral mode of pitch angle 14 degrees. The arms are bluer than the disk in spite of their detection on the NIR images. If the northern side of the galaxy is nearer to us, as is normally assumed, the observed sense of rotation implies trailing arms. The nearly edge-on orientation, high disk surface brightness, and the presence of a complex network of dusty filaments in the optical images, are responsible for the lack of detection of the arms in previous studies.

  10. IC3328 a "dwarf elliptical galaxy" with spiral structure

    CERN Document Server

    Jerjen, H; Binggeli, B; Jerjen, Helmut; Kalnajs, Agris; Binggeli, Bruno

    2000-01-01

    We present the 2-D photometric decomposition of the Virgo galaxy IC3328. The analysis of the global light distribution of this morphologically classified nucleated dwarf elliptical galaxy (dE1,N) reveals a tightly wound, bi-symmetric spiral structure with a diameter of 4.5 kpc, precisely centered on the nucleus of the dwarf. The amplitude of the spiral is only three percent of the dwarf's surface brightness making it the faintest and smallest spiral ever found in a galaxy. In terms of pitch angle and arm winding the spiral is similar to the intermediate-type galaxy M51, but it lacks the dust and prominent HII regions which signal the presence of gas. The visual evidence of a spiral pattern in an early-type dwarf galaxy reopens the question on whether these dwarfs are genuine rotationally supported or anisotropic stellar systems. In the case of IC3328, we argue for a nearly face-on disk (dS0) galaxy with an estimated maximum rotation velocity of v_c,max = 55kms-1. The faintness of the spiral and the small moti...

  11. The relation between bar formation, galaxy luminosity, and environment

    CERN Document Server

    Corsini, E M; Sanchez-Janssen, R; Aguerri, J A L; Zarattini, S

    2013-01-01

    We derive the bar fraction in three different environments ranging from the field to Virgo and Coma clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma cluster are statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on...

  12. Bar-formation as driver of gas inflows in isolated disc galaxies

    CERN Document Server

    Fanali, R; Fiacconi, D; Haardt, F

    2015-01-01

    Stellar bars are a common feature in massive disc galaxies. On a theoretical ground, the response of gas to a bar is generally thought to cause nuclear starbursts and, possibly, AGN activity once the perturbed gas reaches the central super-massive black hole. By means of high resolution numerical simulations we detail the purely dynamical effects that a forming bar exerts on the gas of an isolated disc galaxy. The galaxy is initially unstable to the formation of non-axisymmetric structures, and within 1 Gyr it develops spiral arms that eventually evolve into a central stellar bar on kpc scale. A first major episode of gas inflow occurs during the formation of the spiral arms while at later times, when the stellar bar is establishing, a low density region is carved between the bar co-rotational and inner Lindblad resonance radii. The development of such "dead zone" inhibits further massive gas inflows. Indeed, the gas inflow reaches its maximum during the relatively fast bar formation phase and not, as often a...

  13. CHARACTERISTICS OF SPIRAL ARMS IN LATE-TYPE GALAXIES

    International Nuclear Information System (INIS)

    We have measured the positions of large numbers of H II regions in four nearly face-on, late-type, spiral galaxies: NGC 628 (M74), NGC 1232, NGC 3184, and NGC 5194 (M51). Fitting log-periodic spiral models to segments of each arm yields local estimates of spiral pitch angle and arm width. While pitch angles vary considerably along individual arms, among arms within a galaxy, and among galaxies, we find no systematic trend with galactocentric distance. We estimate the widths of the arm segments from the scatter in the distances of the H II regions from the spiral model. All major arms in these galaxies show spiral arm width increasing with distance from the galactic center, similar to the trend seen in the Milky Way. However, in the outermost parts of the galaxies, where massive star formation declines, some arms reverse this trend and narrow. We find that spiral arms often appear to be composed of segments of ∼5 kpc length, which join to form kinks and abrupt changes in pitch angle and arm width; these characteristics are consistent with properties seen in the large N-body simulations of D'Onghia et al. and others

  14. The formation of disks in massive spiral galaxies

    CERN Document Server

    Hammer, F; Flores, H

    2009-01-01

    The flatness of the rotation curve inside spiral galaxies is interpreted as the imprint of a halo of invisible matter. Using the deepest observations of distant galaxies, we have investigated how large disks could have been formed. Observations include spatially resolved kinematics, detailed morphologies and photometry from UV to mid-IR. Six Giga-years ago, half of the present-day spirals had anomalous kinematics and morphologies that considerably affect the scatter of the Tully Fisher relation. All anomalous galaxies can be modelled through gas-rich, major mergers that lead to a rebuilt of a new disk. The spiral-rebuilding scenario is proposed as a new channel to form large disks in present-day spirals and it accounts for all the observed evolutions since the last 6 Giga-years. A large fraction of the star formation is linked to merging events during their whole durations.

  15. Multi-Wavelength Properties of Barred Galaxies in the Local Universe: Environment and evolution across the Hubble sequence

    CERN Document Server

    Giordano, Lea; Moore, Ben; Saintonge, Amelie

    2011-01-01

    We investigate possible environmental and morphological trends in the $z\\sim0$ bar fraction using two carefully selected samples representative of a low-density environment (the isolated galaxies from the AMIGA sample) and of a dense environment (galaxies in the Virgo cluster). Galaxies span a stellar mass range from $10^8$ to $10^{12}$M$_{\\odot}$ and are visually classified using both high-resolution NIR (H-band) imaging and optical \\texttt{rgb} images. We find that the bar fraction in disk galaxies is independent of environment suggesting that bar formation may occur prior to the formation of galaxy clusters. The bar fraction in early type spirals ($Sa-Sb$) is $\\sim$50%, which is twice as high as the late type spirals ($Sbc-Sm$). The higher bar fraction in early type spirals may be due to the fact that a significant fraction of their bulges are pseudo-bulges which form via the buckling instability of a bar. i.e. a large part of the Hubble sequence is due to secular processes which move disc galaxies from la...

  16. New Low Surface Brightness Dwarf Galaxies Detected Around Nearby Spirals

    OpenAIRE

    Karachentsev, I. D.; Riepe, P.; Zilch, T.; Blauensteiner, M.; Elvov, M.; Hochleitner, P.; Hubl, B.; Kerschhuber, G.; Küppers, S.; Neyer, F.; Pölzl, R.; Remmel, P.; Schneider, O.; Sparenberg, R.; Trulson, U.

    2015-01-01

    We conduct a survey of low surface brightness (LSB) satellite galaxies around the Local Volume massive spirals using long exposures with small amateur telescopes. We identified 27 low and very low surface brightness objects around the galaxies NGC,672, 891, 1156, 2683, 3344, 4258, 4618, 4631, and 5457 situated within 10 Mpc from us, and found nothing new around NGC,2903, 3239, 4214, and 5585. Assuming that the dwarf candidates are the satellites of the neighboring luminous galaxies, their abs...

  17. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    OpenAIRE

    Ziegler, Bodo L.; Kutdemir, Elif; Da Rocha, Cristiano; Böhm, Asmus; Peletier, Reynier F; Verdugo, Miguel

    2009-01-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, positi...

  18. Soft X-ray Emission from the Spiral Galaxy NGC 1313

    OpenAIRE

    Colbert, E. J. M.; Petre, R.; Schlegel, E. M.; Ryder, S.D.

    1995-01-01

    The nearby barred spiral galaxy NGC 1313 has been observed with the PSPC instr- ument on board the ROSAT X-ray satellite. Ten individual sources are found. Three sources (X-1, X-2 and X-3 [SN~1978K]) are very bright (~10^40 erg/s) and are unusual in that analogous objects do not exist in our Galaxy. We present an X-ray image of NGC~1313 and \\xray spectra for the three bright sources. The emission from the nuclear region (R ~< 2 kpc) is dominated by source X-1, which is located ~1 kpc north of...

  19. Scalable Automated Detection of Spiral Galaxy Arm Segments

    CERN Document Server

    Davis, Darren R

    2014-01-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment and perform a least-squares fit of a logarithmic spiral arc to the pixels in the segment. The algorithm takes about 1 minute per galaxy, and can easily be scaled using parallelism. We have run it on all ~644,000 Sloan objects classified as "galaxy" and large enough to observe some structure. Our algorithm is stable in the sense that the statistics across a large sample of galaxies vary smoothly based on algorithmic parameters, although results for individual galaxies can sometimes vary in a non-smooth but easily understood manner. We find a very good correlation between our quantitative description of spiral structure and the qualitative description provided by humans via Galaxy Zoo. In addition, we find that pitch angle often varie...

  20. Spiral structure in nearby galaxies II. comparative analysis and conclusions

    CERN Document Server

    Kendall, S; Kennicutt, R C

    2014-01-01

    This paper presents a detailed analysis of two-armed spiral structure in a sample of galax- ies from the Spitzer Infrared Nearby Galaxies Survey (SINGS), with particular focus on the relationships between the properties of the spiral pattern in the stellar disc and the global struc- ture and environment of the parent galaxies. Following Paper I we have used a combination of Spitzer Space Telescope mid-infrared imaging and visible multi-colour imaging to isolate the spiral pattern in the underlying stellar discs, and we examine the systematic behaviours of the observed amplitudes and shapes (pitch angles) of these spirals. In general, spiral morphology is found to correlate only weakly at best with morphological parameters such as stellar mass, gas fraction, disc/bulge ratio, and vflat. In contrast to weak correlations with galaxy structure a strong link is found between the strength of the spiral arms and tidal forcing from nearby companion galaxies. This appears to support the longstanding suggestion that ei...

  1. The impact of bars on the radial distribution of supernovae in disc galaxies

    Science.gov (United States)

    Hakobyan, A. A.; Karapetyan, A. G.; Barkhudaryan, L. V.; Mamon, G. A.; Kunth, D.; Petrosian, A. R.; Adibekyan, V.; Aramyan, L. S.; Turatto, M.

    2016-07-01

    We present an analysis of the impact of bars on the radial distributions of the different types of supernovae (SNe) in the stellar discs of host galaxies with various morphologies. We find that in Sa-Sbc galaxies, the radial distribution of core-collapse (CC) SNe in barred hosts is inconsistent with that in unbarred ones, while the distributions of SNe Ia are not significantly different. At the same time, the radial distributions of both types of SNe in Sc-Sm galaxies are not affected by bars. We propose that the additional mechanism shaping the distributions of Type Ia and CC SNe can be explained within the framework of substantial suppression of massive star formation in the radial range swept by strong bars, particularly in early-type spirals. The radial distribution of CC SNe in unbarred Sa-Sbc galaxies is more centrally peaked and inconsistent with that in unbarred Sc-Sm hosts, while the distribution of SNe Ia in unbarred galaxies is not affected by host morphology. These results can be explained by the distinct distributions of massive stars in the discs of early-and late-type spirals.

  2. Dynamics of Non-steady Spiral Arms in Disk Galaxies

    Science.gov (United States)

    Baba, Junichi; Saitoh, Takayuki R.; Wada, Keiichi

    2013-01-01

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional N-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms originates in the continual repetition of this nonlinear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the corotation point. Due to interaction with their host arms, the energy and angular momentum of the stars change, thereby causing radial migration of the stars. During this process, the kinetic energy of random motion (random energy) of the stars does not significantly increase, and the disk remains dynamically cold. Owing to this low degree of disk heating, short-lived spiral arms can recurrently develop over many rotational periods. The resultant structure of the spiral arms in the N-body simulations is consistent with the observational nature of spiral galaxies. We conclude that the formation and structure of spiral arms in isolated disk galaxies can be reasonably understood by nonlinear interactions between a spiral arm and its constituent stars.

  3. DYNAMICS OF NON-STEADY SPIRAL ARMS IN DISK GALAXIES

    International Nuclear Information System (INIS)

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional N-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms originates in the continual repetition of this nonlinear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the corotation point. Due to interaction with their host arms, the energy and angular momentum of the stars change, thereby causing radial migration of the stars. During this process, the kinetic energy of random motion (random energy) of the stars does not significantly increase, and the disk remains dynamically cold. Owing to this low degree of disk heating, short-lived spiral arms can recurrently develop over many rotational periods. The resultant structure of the spiral arms in the N-body simulations is consistent with the observational nature of spiral galaxies. We conclude that the formation and structure of spiral arms in isolated disk galaxies can be reasonably understood by nonlinear interactions between a spiral arm and its constituent stars.

  4. Newtonian acceleration scales in spiral galaxies

    CERN Document Server

    Cardone, V F

    2012-01-01

    We revisit the issue of the constancy of the dark matter (DM) and baryonic Newtonian acceleration scales within the DM scale radius by considering a large sample of late - type galaxies. We rely on a Markov Chain Monte Carlo (MCMC) method to estimate the parameters of the halo model and the stellar mass - to - light ratio and then propagate the uncertainties from the rotation curve data to the estimate of the acceleration scales. This procedure allows us to compile a catalog of 58 objects with estimated values of the $B$ band absolute magnitude $M_B$, the virial mass $M_{vir}$, the DM and baryonic Newtonian accelerations (denoted as $g_{DM}(r_0)$ and $g_{bar}(r_0)$, respectively) within the scale radius $r_0$ which we use to investigate whether it is possible to define a universal acceleration scale. We find a weak but statistically meaningful correlation with $M_{vir}$ thus making us argue against the universality of the acceleration scales. However, the results somewhat depend on the sample adopted so that ...

  5. 21 centimeter study of spiral galaxies in the Coma supercluster

    International Nuclear Information System (INIS)

    High-sensitivity, 21 cm line observations of 130 galaxies in the Coma/A1367 Supercluster region are presented and used to study the large-scale distribution of galaxies in the direction of the Coma Supercluster and the H I content in spiral galaxies as a function of the local galaxy density. Groups of galaxies are found to form a quasi-continuous structure that connects the Local Supercluster to the Coma Supercluster. This structure is composed of real filaments only in the vicinity of the Coma Cluster. Spiral galaxies in the surveyed groups and multiple systems have H I content not dissimilar from that of isolated galaxies. Galaxies within about 1 Abell radius from the Coma Cluster contain about three times less hydrogen on average than isolated galaxies. There is a strong tendency for galaxies that are more severely H I-depleted to be redder and of earlier Hubble type. In the Coma Cluster a considerable fraction of late-type, blue galaxies have large deficiency parameters. 51 references

  6. Accretion, radial flows and abundance gradients in spiral galaxies

    CERN Document Server

    Pezzulli, Gabriele

    2015-01-01

    The metal-poor gas continuously accreting onto the discs of spiral galaxies is unlikely to arrive from the intergalactic medium (IGM) with exactly the same rotation velocity as the galaxy itself and even a small angular momentum mismatch inevitably drives radial gas flows within the disc, with significant consequences to galaxy evolution. Here we provide some general analytic tools to compute accretion profiles, radial gas flows and abundance gradients in spiral galaxies as a function of the angular momentum of accreting material. We generalize existing solutions for the decomposition of the gas flows, required to reproduce the structural properties of galaxy discs, into direct accretion from the IGM and a radial mass flux within the disc. We then solve the equation of metallicity evolution in the presence of radial gas flows with a novel method, based on characteristic lines, which greatly reduces the numerical demand on the computation and sheds light on the crucial role of boundary conditions on the abunda...

  7. Gas and stellar spiral structures in tidally perturbed disc galaxies

    CERN Document Server

    Pettitt, Alex R; Wadsley, James W

    2016-01-01

    Tidal interactions between disc galaxies and low mass companions are an established method for generating galactic spiral features. In this work we present a study of the structure and dynamics of spiral arms driven in interactions between disc galaxies and perturbing companions in 3-D N-body/smoothed hydrodynamical numerical simulations. Our specific aims are to characterize any differences between structures formed in the gas and stars from a purely hydrodynamical and gravitational perspective, and to find a limiting case for spiral structure generation. Through analysis of a number of different interacting cases, we find that there is very little difference between arm morphology, pitch angles and pattern speeds between the two media. The main differences are a minor offset between gas and stellar arms, clear spurring features in gaseous arms, and different radial migration of material in the stronger interacting cases. We investigate the minimum mass of a companion required to drive spiral structure in a ...

  8. The black hole mass function derived from local spiral galaxies

    International Nuclear Information System (INIS)

    We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of black hole evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of black holes since the epoch of maximum quasar activity. The sample is defined by a limiting luminosity (redshift-independent) distance, DL = 25.4 Mpc (z = 0.00572) and a limiting absolute B-band magnitude, MB=−19.12. These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch-angle distribution function may be useful in the study of the morphology of late-type galaxies. We then use an established relationship between the logarithmic spiral arm pitch angle and the mass of the central SMBH in a host galaxy in order to estimate the mass of the 128 respective SMBHs in this volume-limited sample. This result effectively gives us the distribution of mass for SMBHs residing in spiral galaxies over a lookback time, tL ≤ 82.1 h67.77−1 Myr and contained within a comoving volume, VC = 3.37 × 104 h67.77−3 Mpc3. We estimate that the density of SMBHs residing in spiral galaxies in the local universe is ρ=5.54−2.73+6.55 × 104 h67.773 M☉ Mpc–3. Thus, our derived cosmological SMBH mass density for spiral galaxies is ΩBH=4.35−2.15+5.14 × 10–7 h67.77. Assuming that black holes grow via baryonic accretion, we predict that 0.0020−0.0010+0.0023 h67.773 % of the universal baryonic inventory (

  9. Turbulence and Star Formation in a Sample of Spiral Galaxies

    Science.gov (United States)

    Maier, Erin R.; Hunter, Deidre Ann; Chien, Li-Hsin

    2016-01-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. (2010) as applied to the Small Magellanic Cloud, we use the third and fourth statistical moments, skewness and kurtosis, which are indicators of structures caused by turbulence, to examine the integrated neutral hydrogen (Hι) column density of a sample of spiral galaxies selected from The Hι Nearby Galaxy Survey (THINGS, Walter et al. 2008). We examine the kurtosis and skewness values of each galaxy as a whole, as well as their variation as a function of radius and in discrete sub-regions defined by a square, moving 'kernel,' essentially splitting each galaxy into a grid. We then create individual grid maps of kurtosis and skewness for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with maps of each galaxy's far-ultraviolet (FUV) image, taken by the Galaxy Evolution Explorer (GALEX) satellite. We find that the moments are largely uniform across the galaxies: the variation does not appear to trace any star forming regions. This may, however, be due to the spatial resolution of our analysis, which could potentially limit the scale of turbulent motions to at most ~700 pc. From our analysis of the comparison between the two moments themselves, we find that the gas motions in our sample galaxies are largely supersonic. This analysis shows that Burkhart et al. (2010)'s methods may be applied not just to dwarf galaxies but normal spiral galaxies as well.We acknowledge the NSF for their funding of this work through their Research Experience for Undergraduates (REU) program (Grant No. AST-1461200).

  10. Photometric scaling relations of lenticular and spiral galaxies

    CERN Document Server

    Laurikainen, E; Buta, R; Knapen, J H; Comerón, S

    2010-01-01

    Photometric scaling relations are studied for S0 galaxies and compared with those for spirals. New 2D K_s-band multi-component decompositions are presented for 122 early-type disk galaxies. Combining with our previous decompositions, the final sample consists of 175 galaxies. As a comparison sample we use the Ohio State University Bright Spiral Galaxy Survey (OSUBSGS), for which similar decompositions have previously been made by us. Our main results are: (1) Important scaling relations are present, indicating that the formative processes of bulges and disks in S0s are coupled like has been previously found for spirals. (2) We obtain median r_{eff}/h_r = 0.20, 0.15 and 0.10 for S0, S0/a-Sa and Sab-Sc galaxies: these are smaller than predicted by simulation models in which bulges are formed by galaxy mergers. (3) The properties of bulges of S0s are different from the elliptical galaxies, which is manifested in the M_K(bulge) vs r_{eff} relation, in the photometric plane, and to some extent also in the Kormendy...

  11. Star formation rates of spiral galaxies in the Cosmic Web

    Science.gov (United States)

    Alpaslan, Mehmet; Marcum, Pamela M.; Galaxy And Mass Assembly (GAMA)

    2016-01-01

    We look for shifts in stellar mass and star formation rate along filaments in the cosmic web by examining the stellar masses and UV-derived star formation rates of 1,799 ungrouped and unpaired spiral galaxies from the Galaxy And Mass Assembly (GAMA) survey that reside in filaments. We devise multiple distance metrics to characterise the complex geometry of filaments, and find that galaxies closer to the orthogonal core of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. We also find that these peripheral galaxies have higher specific star formations at a given mass. Our results suggest a model in which gas accretion from voids onto filaments is primarily in an orthogonal direction. While the star formation rates of spiral galaxies in filaments are susceptible to their locations, we find that the global star formation rates of galaxies in different large scale environments are similar to each other. The primary discriminant in star formation rates is therefore the stellar mass of each spiral galaxy, as opposed to its large scale environment.

  12. STAR FORMATION IN PARTIALLY GAS-DEPLETED SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Broadband B and R and Hα images have been obtained with the 4.1 m SOAR telescope atop Cerro Pachon, Chile, for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low-density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (H I) data obtained with the Arecibo 305 m radio telescope, acquired by Levy et al. (2007) and by Springob et al. (2005b), we study the star formation rates in disk galaxies as a function of their H I deficiency. To quantify H I deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of Hα flux to R-band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more H I-deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more H I-deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the H I-depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas depletion and the size of the Hα disk (relative to the R-band disk); H I-poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the Hα disks of gas-poor galaxies than in gas-rich spirals. Thus, both disk truncation and lowered SSFR levels within the star-forming part of the disks (aside from the enhanced nuclear SSFR) correlate with H I deficiency, and both phenomena are found to

  13. Spiral galaxy distance indicators based on near-infrared photometry

    CERN Document Server

    De Grijs, R

    1999-01-01

    We compare two methods of distance determination to spiral galaxies using optical/near-infrared (NIR) observations, the (I-K) versus M_K colour - absolute magnitude (CM) relation and the I and K-band Tully-Fisher relation (TFR). Dust-free colours and NIR absolute magnitudes greatly enhance the usefulness of the NIR CM relation as a distance indicator for moderately to highly inclined_spiral_ galaxies_in the field_ (inclinations between ~ 80 and 90 deg); by avoiding contamination by dust the scatter in the CM relation is significantly reduced, compared to similar galaxy samples published previously. The CM relation can be used to determine distances to field spiral galaxies with M_K > -25.5, to at least M_K ~ -20. Our results, supplemented with previously published observations for which we can - to some degree - control the effects of extinction, are consistent with a universal nature of the CM relation for field spiral galaxies. High-resolution observations done with the Hubble Space Telescope can provide a ...

  14. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    CERN Document Server

    Robertson, Paul; Blanc, Guillermo A

    2011-01-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to ISM-ICM interaction, albeit to a lesser degree. Based on the abundances of 3 H I deficient spirals and 2 H I normal spirals, we observe a heavy element abundance offset of +0.13\\pm0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log(O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our resul...

  15. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A., E-mail: paul@astro.as.utexas.edu, E-mail: shields@astro.as.utexas.edu, E-mail: gblancm@astro.as.utexas.edu [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

    2012-03-20

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 {+-} 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  16. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    International Nuclear Information System (INIS)

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 ± 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  17. Tidal origin of spiral arms in galaxies orbiting a cluster

    CERN Document Server

    Semczuk, Marcin; del Pino, Andres

    2016-01-01

    One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the potential of a galaxy cluster. Using $N$-body simulations we investigate the formation and evolution of spiral arms in a Milky Way-like galaxy orbiting a Virgo-like cluster. The galaxy is placed on a few orbits of different size but similar eccentricity and its evolution is followed for 10 Gyr. The tidally induced, two-armed, approximately logarithmic spiral structure forms on each of them during the pericenter passages. The spiral arms dissipate and wind up with time, to be triggered again at the next pericenter passage. We confirm this transient and recurrent nature of the arms by analyzing the time evolution of the pitch angle and the arm strength. We find that the strongest arms are formed on the tightest orbit, however they wind up rather quickly and are disturbed by another p...

  18. Spiral galaxies in clusters. III. Gas-rich galaxies in the Pegasus I cluster of galaxies

    International Nuclear Information System (INIS)

    We report the results of a 21-cm and optical survey of disk galaxies in the vicinity of the Pegasus I cluster of galaxies. The color--gas content relation [log(M/sub H//L/sub B/) vs (B-V)/sup T/0 ] for this particular cluster reveals the presence of a substantial number of blue, gas-rich galaxies. With few exceptions, the disk systems in Pegasus I retain large amounts of neutral hydrogen despite their presence in a cluster. This directly shows that environmental processes have not yet removed substantial amounts of gas from these disk galaxies. We conclude that the environment has had little or no observable effect upon the evolution of disk galaxies in Pegasus I. The overall properties of the Pegasus I spirals are consistent with the suggestion that this cluster is now at an early stage in its evolution

  19. Arm & Interarm Star Formation in Spiral Galaxies

    CERN Document Server

    Foyle, Kelly; Walter, Fabian; Leroy, Adam

    2010-01-01

    We investigate the relationship between spiral arms and star formation in the grand-design spirals NGC 5194 and NGC 628 and in the flocculent spiral NGC 6946. Filtered maps of near-IR (3.6 micron) emission allow us to identify "arm regions" that should correspond to regions of stellar mass density enhancements. The two grand-design spirals show a clear two-armed structure, while NGC 6946 is more complex. We examine these arm and interarm regions, looking at maps that trace recent star formation - far-ultraviolet (GALEX NGS) and 24 micron emission (Spitzer, SINGS) - and cold gas - CO (Heracles) and HI (Things). We find the star formation tracers and CO more concentrated in the spiral arms than the stellar 3.6 micron flux. If we define the spiral arms as the 25% highest pixels in the filtered 3.6 micron images, we find that the majority (60%) of star formation tracers occurs in the interarm regions; this result persists qualitatively even when considering the potential impact of finite data resolution and diffu...

  20. The Dynamical Relationship Between the Bar and Spiral Patterns of NGC 1365

    CERN Document Server

    Speights, Jason C

    2016-01-01

    Theories that attempt to explain the dynamical relationship between bar and spiral patterns in galactic disks make different predictions about the radial profile of the pattern speed. These are tested for the H-alpha bar and spiral patterns of NGC 1365. The radial profile of the pattern speed is measured by fitting mathematical models that are based on the Tremaine-Weinberg method. The results show convincing evidence for the bar rotating at a faster rate than the spiral pattern, inconsistent with a global wave mode or a manifold. There is evidence for mode coupling of the bar and spiral patterns at the overlap of corotation and inner Lindblad resonances, but the evidence is unreliable and inconsistent. The results are the most consistent with the bar and spiral patterns being dynamically distinct features. The pattern speed of the bar begins near an ILR and ends near the corotation resonance. The radial profile of the pattern speed beyond the bar most closely resembles what is expected for coupled spiral mod...

  1. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disc morphology

    Science.gov (United States)

    Willett, Kyle W.; Schawinski, Kevin; Simmons, Brooke D.; Masters, Karen L.; Skibba, Ramin A.; Kaviraj, Sugata; Melvin, Thomas; Wong, O. Ivy; Nichol, Robert C.; Cheung, Edmond; Lintott, Chris J.; Fortson, Lucy

    2015-05-01

    We measure the stellar mass-star formation rate (SFR) relation in star-forming disc galaxies at z ≤ 0.085, using Galaxy Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disc, and show that both the slope and dispersion of the M⋆-SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ˜0.3 dex; this is significantly smaller than the increase seen in merging systems at z > 1. Of the galaxies lying significantly above the M⋆-SFR relation in the local Universe, more than 50 per cent are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

  2. Revealing galactic scale bars with the help of Galaxy Zoo

    Science.gov (United States)

    Masters, Karen L.

    2015-03-01

    We use visual classifications of the brightest 250,000 galaxies in the Sloan Digital Sky Survey Main Galaxy Sample provided by citizen scientists via the Galaxy Zoo project (www.galaxyzoo.org, Lintott et al. 2008) to identify a sample of local disc galaxies with reliable bar identifications. These data, combined with information on the atomic gas content from the ALFALFA survey (Haynes et al. 2011) show that disc galaxies with higher gas content have lower bar fractions. We use a gas deficiency parameter to show that disc galaxies with more/less gas than expected for their stellar mass are less/more likely to host bars. Furthermore, we see that at a fixed gas content there is no residual correlation between bar fraction and stellar mass. We argue that this suggests previously observed correlations between galaxy colour/stellar mass and (strong) bar fraction (e.g. from the sample in Masters et al. 2011, and also see Nair & Abraham 2010) could be driven by the interaction between bars and the gas content of the disc, since more massive, optically redder disc galaxies are observed to have lower gas contents. Furthermore we see evidence that at a fixed gas content the global colours of barred galaxies are redder than those of unbarred galaxies. We suggest that this could be due to the exchange of angular momentum beyond co-rotation which might stop a replenishment of gas from external sources, and act as a source of feedback to temporarily halt or reduce the star formation in the outer parts of barred discs. These results (published as Masters et al. 2012) combined with those of Skibba et al. (2012), who use the same sample to show a clear (but subtle and complicated) environmental dependence of the bar fraction in disc galaxies, suggest that bars are intimately linked to the evolution of disc galaxies.

  3. Calculating the submillimeter emissivity of dust grains in spiral galaxies

    OpenAIRE

    Xilouris, E. M.

    2005-01-01

    We use the radiation transfer simulation of Xilouris et al. (1999) to constrain the quantity of dust in three nearby spiral galaxies (NGC 4013, NGC 5907 and NGC 891). The predicted visual optical depth from the model is compared with the thermal continuum radiation detected from these galaxies at 850 microns. This comparison yields the emissivity of dust grains in the submillimeter waveband which is a factor 4 higher than the benchmark, semi-empirical model of Draine & Lee (1984). Our estimat...

  4. Star Formation in the ISO Atlas of Spiral Galaxies

    CERN Document Server

    Bendo, G J; Wells, M; Gallais, P; Haas, M; Heras, A M; Klaas, U; Laureijs, R J; Leech, K; Lemke, D; Metcalfe, L; Rowan-Robinson, M; Schulz, B; Telesco, C M; Bendo, George J.; Joseph, Robert D.; Wells, Martyn; Gallais, Pascal; Haas, Martin; Heras, Ana M.; Klaas, Ulrich; Laureijs, Rene J.; Leech, Kieron; Lemke, Dietrich; Metcalfe, Leo; Rowan-Robinson, Michael; Schulz, Bernhard; Telesco, Charles

    2002-01-01

    We investigate star formation along the Hubble sequence using the ISO Atlas of Spiral Galaxies. Using mid-infrared and far-infrared flux densities normalized by K-band flux densities as indicators of recent star formation, we find several trends. First, star formation activity is stronger in late-type (Sc - Scd) spirals than in early-type (Sa - Sab) spirals. This trend is seen both in nuclear and disk activity. These results confirm several previous optical studies of star formation along the Hubble sequence but conflict with the conclusions of most of the previous studies using IRAS data, and we discuss why this might be so. Second, star formation is significantly more extended in later-type spirals than in early-type spirals. We suggest that these trends in star formation are a result of differences in the gas content and its distribution along the Hubble sequence, and it is these differences that promote star formation in late-type spiral galaxies. We also search for trends in nuclear star formation relate...

  5. Kinematic classification of non-interacting spiral galaxies

    CERN Document Server

    Wiegert, Theresa

    2013-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous...

  6. Oxygen abundances and the chemical evolution of spiral galaxies

    OpenAIRE

    Tosi., M; Angeles I. Díaz

    1983-01-01

    This is an electronic version of an article published in Memorie della Società Astronomica Italiana. Tosi, M. and A. I. Díaz. Oxygen abundances and the chemical evolution of spiral galaxies. Memorie della Società Astronomica Italiana 54, 4 (1983): 889-890

  7. Multifrequency study of spiral galaxies in the Coma supercluster

    International Nuclear Information System (INIS)

    The spectral characteristics of normal spiral galaxies are examined, focusing on the relationships between emission mechanisms in the radio continuum, the 21-cm H line, FIR, NIR, and optical bands. Also, the relationship between these mechanisms and the environmental properties of the galaxy is discussed. The study uses a sample from the Coma supercluster, focusing on the three-dimensional structure of the Coma supercluster, the dependence of average radio continuum and FIR luminosities on star formation, and the H I characteristics of galaxies in the Coma superlcuster. 36 refs

  8. Star Formation in Partially Gas-Depleted Spiral Galaxies

    CERN Document Server

    Rose, James A; Miner, Jesse; Levy, Lorenza

    2009-01-01

    Broadband B and R and H-alpha images have been obtained with the 4.1-m SOAR telescope atop Cerro Pachon, Chile for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (HI) data obtained with the Arecibo 305-m radiotelescope, acquired by Levy et al. (2007) and by Springob et al. (2005a), we study the star formation rates in disk galaxies as a function of their HI deficiency. To quantify HI deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of H-alpha flux to R band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more HI-deficient galaxies. This correlation appears to extend from...

  9. Turbulence and Star Formation in a Sample of Spiral Galaxies

    CERN Document Server

    Maier, Erin; Hunter, Deidre A

    2016-01-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. (2010) on the Small Magellanic Cloud, we use the third and fourth statistical moments, as indicators of structures caused by turbulence, to examine the neutral hydrogen (HI) column density of a sample of spiral galaxies selected from The HI Nearby Galaxy Survey (THINGS, Walter et al. 2008). We apply the statistical moments in three different methods- the galaxy as a whole, divided into a function of radii and then into grids. We create individual grid maps of kurtosis for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with their far-ultraviolet images taken by the Galaxy Evolution Explorer (GALEX) satellite. We find that the moments are largely uniform across the galaxies, in which the variatio...

  10. How can double-barred galaxies be long-lived?

    CERN Document Server

    Wozniak, Herve

    2015-01-01

    Double-barred galaxies account for almost one third of all barred galaxies, suggesting that secondary stellar bars, which are embedded in large-scale primary bars, are long-lived structures. However, up to now it has been hard to self-consistently simulate a disc galaxy that sustains two nested stellar bars for longer than a few rotation periods. N-body/hydrodynamical simulations including star formation recipes have been performed. Their properties have been compared with the most recent observational data in order to prove that they are representative of double-barred galaxies, even SB0. Overlaps in dynamical resonances and bar modes have been looked for using Fourier spectrograms. Double-barred galaxies have been successfully simulated with lifetimes as long as 7 Gyr. The stellar population of the secondary bar is younger on average than for the primary large-scale bar. An important feature of these simulations is the absence of any resonance overlap for several Gyr. In particular, there is no overlap betw...

  11. The flaring HI disk of the nearby spiral galaxy NGC 2683

    CERN Document Server

    Vollmer, B; Ibata, R

    2015-01-01

    New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination; (iv) an exponential flare; and (v) a low surface-density gas ring. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the ...

  12. Gas and stellar spiral structures in tidally perturbed disc galaxies

    Science.gov (United States)

    Pettitt, Alex R.; Tasker, Elizabeth J.; Wadsley, James W.

    2016-06-01

    Tidal interactions between disc galaxies and low-mass companions are an established method for generating galactic spiral features. In this work, we present a study of the structure and dynamics of spiral arms driven in interactions between disc galaxies and perturbing companions in 3D N-body/smoothed hydrodynamical numerical simulations. Our specific aims are to characterize any differences between structures formed in the gas and stars from a purely hydrodynamical and gravitational perspective, and to find a limiting case for spiral structure generation. Through analysis of a number of different interacting cases, we find that there is very little difference between arm morphology, pitch angles and pattern speeds between the two media. The main differences are a minor offset between gas and stellar arms, clear spurring features in gaseous arms, and different radial migration of material in the stronger interacting cases. We investigate the minimum mass of a companion required to drive spiral structure in a galactic disc, finding the limiting spiral generation cases with companion masses of the order of 1 × 109 M⊙, equivalent to only 4 per cent of the stellar disc mass, or 0.5 per cent of the total galactic mass of a Milky Way analogue.

  13. Magnetic field evolution and reversals in spiral galaxies

    CERN Document Server

    Dobbs, C L; Pettitt, A R; Bate, M R; Tricco, T

    2016-01-01

    We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find magnetic field reversals occur when the velocity jump across the spiral shock is above $\\approx$20km s$^{-1}$, occurring where the velocity change is highest, typically at the inner Lindblad resonance (ILR) in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the co-rotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at a radii of around 4--6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is ...

  14. Diffuse X-ray emission in spiral galaxies

    CERN Document Server

    Tyler, K; La Page, A; Rieke, G H

    2003-01-01

    We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate inclination spiral galaxies to the morphology seen in Halpha, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a rounder morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or Halpha and so implies that the X-ray emission is associated with recent active star formation. We see no strong evidence for X-ray emission trailing the location of high mass star formation in spiral arms. However, population synthesis models predict a high mechanical energy output rate from supernovae for a time period that is about 10 times longer than the lifetime of massive ionizing stars, conflicting with the narrow appearance of the arms in X-rays. The fraction of supernova energy that goes into heating the ISM must depend on environment and is probably higher n...

  15. Selection effects in the bivariate brightness distribution for spiral galaxies

    International Nuclear Information System (INIS)

    The joint distribution of total luminosity and characteristic surface brightness (the bivariate brightness distribution) is investigated for a complete sample of spiral galaxies in the Virgo cluster. The influence of selection and physical limits of various kinds on the apparent distribution are detailed. While the distribution of surface brightness for bright galaxies may be genuinely fairly narrow, faint galaxies exist right across the (quite small) range of accessible surface brightnesses so no statement can be made about the true extent of the distribution. The lack of high surface brightness bright galaxies in the Virgo sample relative to an overall RC2 sample (mostly field galaxies) supports the contention that the star-formation rate is reduced in the inner region of the cluster for environmental reasons. (author)

  16. The impact of bars on the radial distribution of supernovae in disc galaxies

    CERN Document Server

    Hakobyan, A A; Barkhudaryan, L V; Mamon, G A; Kunth, D; Petrosian, A R; Adibekyan, V; Aramyan, L S; Turatto, M

    2016-01-01

    We present an analysis of the impact of bars on the radial distributions of the different types of supernovae (SNe) in the stellar discs of host galaxies with various morphologies. We find that in Sa-Sbc galaxies, the radial distribution of core-collapse (CC) SNe in barred hosts is inconsistent with that in unbarred ones, while the distributions of SNe Ia are not significantly different. At the same time, the radial distributions of both types of SNe in Sc-Sm galaxies are not affected by bars. We propose that the additional mechanism shaping the distributions of Type Ia and CC SNe can be explained within the framework of substantial suppression of massive star formation in the radial range swept by strong bars, particularly in early-type spirals. The radial distribution of CC SNe in unbarred Sa-Sbc galaxies is more centrally peaked and inconsistent with that in unbarred Sc-Sm hosts, while the distribution of SNe Ia in unbarred galaxies is not affected by host morphology. These results can be explained by the ...

  17. The surface brightness of spiral galaxies

    International Nuclear Information System (INIS)

    The intrinsic surface brightness Ssub(e) of 500 disc galaxies (0<=T<=9) drawn from the Second Reference Catalogue is computed and it is shown that Ssub(e) does not correlate significantly with Msub(B), (B-V) or type. This is consistent with the notion that there is a heavy selection bias in favour of disc galaxies with that particular surface brightness which allows inclusion in the catalogue over the largest volume of space. (author)

  18. Structure and Inclination Angle of the Spiral Galaxy M31

    Institute of Scientific and Technical Information of China (English)

    MA Jun

    2001-01-01

    The mathematical form, the symmetry of the spiral structure, and the projection of the galactic disc on the image of the spiral galaxy M31 have been directly studied. It is found that M31 has two symmetric arms, i.e. the pitch angles of the two arms are nearly equal; these are 7.7° and 8.0°, respectively. Using the method proposed in this letter, the inclination angle of the galactic disc ofM31 is also obtained, which is 77.5° and is in good agreement with previously published results.

  19. The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

    CERN Document Server

    Keel, William C; Holwerda, Benne W; Lintott, Chris J; Schawinski, Kevin

    2014-01-01

    (Abridged) The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use GALEX, XMM Optical Monitor, and HST data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with candidates provided by Galaxy Zoo participants. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law close to the Calzetti et al. (1994) form; the UV slope for the overall sample is substantially shallower than found by Wild et al. (2011), a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives accuracy almost equal ...

  20. Mass Distribution and Bar Formation in Growing Disk Galaxy Models

    CERN Document Server

    Berrier, Joel C

    2016-01-01

    We report idealized simulations that mimic the growth of galaxy disks embedded in responsive halos and bulges. The disks manifested an almost overwhelming tendency to form strong bars that we found very difficult to prevent. We found that fresh bars formed in growing disks after we had destroyed the original, indicating that bar formation also afflicts continued galaxy evolution, and not just the early stages of disk formation. This behavior raises still more insistently the previously unsolved question of how some galaxies avoid bars. Since our simulations included only collisionless star and halo particles, our findings may apply to gas-poor galaxies only; however the conundrum persists for the substantial unbarred fraction of those galaxies. Our original objective was to study how internal dynamics rearranged the distribution of mass in the disk as a generalization of our earlier study with rigid spherical components. With difficulty, we were able to construct some models that were not strongly influenced ...

  1. Forming Double-barred Galaxies From Dynamically Cool Inner Disks

    CERN Document Server

    Du, Min; Debattista, Victor P

    2015-01-01

    About one third of early-type barred galaxies host small-scale secondary bars. The formation and evolution of such double-barred galaxies remain far from being well understood. In order to understand the formation of such systems, we explore a large parameter space of isolated pure-disk simulations. We show that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady secondary bar while the outer disk forms a large-scale primary bar. The independent bar instabilities of inner and outer disks result in long-lived double-barred structures whose dynamical properties are comparable with observations. This formation scenario indicates that the secondary bar might form from the general bar instability, the same as the primary bar. Under some circumstances, the interaction of the bars and the disk leads to the two bars aligning or single, nuclear, bars only. Simulations that are cool enough of the center to experience clump instabilities may also generate steady double-barred ga...

  2. Extended HI disks in nearby spiral galaxies

    OpenAIRE

    Bosma, A.

    2016-01-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a "tilted ring model" allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both t...

  3. Extended HI disks in nearby spiral galaxies

    CERN Document Server

    Bosma, A

    2016-01-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a "tilted ring model" allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  4. Evolution of Gas Across Spiral Arms in the Whirlpool Galaxy

    Science.gov (United States)

    Louie, Melissa Nicole

    To investigate the dynamic evolution of gas across spiral arms, we conducted a detailed study of the gas and star formation along the spiral arms in the Whirlpool Galaxy, M51. This nearby, face-on spiral galaxy provides a unique laboratory to study the relationship between gas dynamics and star formation. The textbook picture of interstellar medium (ISM) evolution is rapidly changing. Molecular gas was once believed to form along spiral arms from the diffuse atomic gas in the inter-arm regions. Star formation occurs within giant molecular clouds during spiral arm passage. Lastly, the molecular gas is photo-dissociated back into atomic gas by massive stars on the downstream side of the spiral arm. Recent evidence, however, is revealing a new picture of the interstellar medium and the process of star formation. We seek development of a new picture by studying the development and evolution of molecular gas and the role of large scale galactic dynamics in organizing the interstellar medium. This thesis begins by presenting work measuring the geometrical offsets between interstellar gas and recent star formation. Interstellar gas is traced by atomic hydrogen and carbon monoxide (CO). Star formation is traced by ionized hydrogen recombination lines and infrared emission from dust warmed by young bright stars. Measuring these offsets can help determine the underlying large scale galactic dynamics. Along the spiral arms in M51, offsets between CO and the star formation tracers suggest that gas is flowing through the spiral arms, but the offsets do not show the expected signature of a single pattern speed and imply a more complicated pattern. This thesis also examines the intermediate stages of gas evolution, by studying a denser component of the ISM closer to which stars will form. Only a small percent of the bulk molecular gas will become dense enough to form stars. HCN and HCO+ probe densities ˜104 cm-3, where as the bulk gas is 500 cm-3. This thesis looks at HCN and

  5. Dark matter within high surface brightness spiral galaxies

    CERN Document Server

    Kranz, T; Rix, H W; Kranz, Thilo; Slyz, Adrianne; Rix, Hans-Walter

    2003-01-01

    We present results from a detailed dynamical analysis of five high surface brightness, late type spirals, studied with the aim to quantify the luminous-to-dark matter ratio inside their optical radii. The galaxies' stellar light distribution and gas kinematics have been observed and compared to hydrodynamic gas simulations, which predict the 2D gas dynamics arising in response to empirical gravitational potentials, which are combinations of differing stellar disk and dark halo contributions. The gravitational potential of the stellar disk was derived from near-infrared photometry, color-corrected to constant (M/L); the dark halo was modelled by an isothermal sphere with a core. Hydrodynamic gas simulations were performed for each galaxy for a sequence of five different mass fractions of the stellar disk and for a wide range of spiral pattern speeds. These two parameters mainly determine the modelled gas distribution and kinematics. The agreement between the non-axisymmetric part of the simulated and observed ...

  6. Influence of baryonic physics in simulations of spiral galaxies

    International Nuclear Information System (INIS)

    The modelling of baryonic physics in numerical simulations of disc galaxies allows us to study the evolution of the different components, the physical state of the gas and the star formation. The present work aims at investigating in particular the role of the cold and dense molecular phase, which could play a role of gas reservoir in the outer galaxy discs, with low star formation efficiency. After a presentation of galaxies with a focus on spiral galaxies, their interstellar medium and dynamical evolution, we review the current state of hydrodynamical numerical simulations and the implementation of baryonic physics. We then present the simulations we performed. These include the cooling to low temperatures, and a molecular hydrogen component. The cooling functions we use include cooling by metals, for temperatures as low as 100 K, and cooling by H2 due to collisions with H, He and other H2 molecules. We use a TreeSPH type code that considers the stellar and gaseous components and black matter as particles. We especially test the impact of the presence of molecular hydrogen in simulations with several feedback efficiencies, and find that the molecular hydrogen allows in all cases some slow stellar formation to occur in the outer disc, with an effect on the vertical structure of the disc that is sensitive to the feedback efficiency. Molecular hydrogen is therefore able to play the role of gas reservoir in external parts of spiral galaxies, which accrete gas from cosmic filaments all along their lives

  7. An Atlas for Structural Studies of Spiral Galaxies

    OpenAIRE

    Courteau, Stephane

    1999-01-01

    This is an announcement of a new database of structural properties for 304 late-type (Sb-Sc) spiral galaxies drawn from the UGC catalogue. These data were compiled from the kinematic and photometric studies of Courteau (1996, 1997), and are made available to the community via the Canadian Astronomy Data Centre. The data base contains redshift information and Tully-Fisher distances, various measures of optical (Halpha) line width and rotational velocity, isophotal diameters and magnitudes, dis...

  8. The warm ionized medium in spiral galaxies

    CERN Document Server

    Haffner, L M; Beckman, J E; Wood, K; Slavin, J D; Giammanco, C; Madsen, G J; Zurita, A; Reynolds, R J

    2009-01-01

    This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo Observatory in August 2004. This review is in recognition of Carl's long standing interest in and advocacy for studies of the ionized as well as the neutral components of the interstellar medium.

  9. Evolution of spiral galaxies in modified gravity

    OpenAIRE

    Tiret, O; Combes, F

    2007-01-01

    We compare N-body simulations of isolated galaxies performed in both frameworks of modified Newtonian dynamics (MOND) and Newtonian gravity with dark matter (DM). We have developed a multigrid code able to efficiently solve the modified Poisson equation derived from the Lagrangian formalism AQUAL. We take particular care of the boundary conditions that are a crucial point in MOND. The 3-dimensional dynamics of initially identical stellar discs is studied in both models. In Newtonian gravity t...

  10. Estimating non-circular motions in barred galaxies using numerical N-body simulations

    CERN Document Server

    Randriamampandry, Toky; Carignan, Claude; Deg, Nathan

    2015-01-01

    The observed velocities of the gas in barred galaxies are a combination of the azimuthally-averaged circular velocity and non-circular motions, primarily caused by gas streaming along the bar. These non-circular flows must be accounted for before the observed velocities can be used in mass modeling. In this work, we examine the performance of the tilted-ring method and the DiskFit algorithm for transforming velocity maps of barred spiral galaxies into rotation curves (RCs) using simulated data. We find that the tilted-ring method, which does not account for streaming motions, under/over-estimates the circular motions when the bar is parallel/perpendicular to the projected major axis. DiskFit, which does include streaming motions, is limited to orientations where the bar is not-aligned with either the major or minor axis of the image. Therefore, we propose a method of correcting RCs based on numerical simulations of galaxies. We correct the RC derived from the tilted-ring method based on a numerical simulation...

  11. The Black Hole Mass Function Derived from Local Spiral Galaxies

    CERN Document Server

    Davis, Benjamin L; Johns, Lucas; Shields, Douglas W; Hartley, Matthew T; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S; Lacy, Claud H S

    2014-01-01

    We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the Local Universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the Southern Hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of SMBH evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of SMBHs since the epoch of maximum quasar activity. A luminosity distance $\\leq$ 25.4 $Mpc$ and an absolute B-band magnitude $\\leq$ -19.12 define the sample. These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch angle distribution function may be useful in...

  12. Prominent spiral arms in the gaseous outer galaxy disks

    CERN Document Server

    Bertin, G

    2009-01-01

    Context: Several spiral galaxies, as beautifully exhibited by the case of NGC 6946, display a prominent large-scale spiral structure in their gaseous outer disk. Such structure is often thought to pose a dynamical puzzle, because grand-design spiral structure is traditionally interpreted as the result of density waves carried mostly in the stellar disk. Aims. Here we argue that the outer spiral arms in the cold gas outside the bright optical disk actually have a natural interpretation as the manifestation of the mechanism that excites grand-design spiral structure in the main, star-dominated body of the disk: the excitation is driven by angular momentum transport to the outer regions, through trailing density waves outside the corotation circle that can penetrate beyond the Outer Lindblad Resonance in the gaseous component of the disk. Methods: Because of conservation of the density wave action, these outgoing waves are likely to become more prominent in the outer disk and eventually reach non-linear amplitud...

  13. Dynamics of Non-Steady Spiral Arms in Disk Galaxies

    CERN Document Server

    Baba, Junichi; Wada, Keiichi

    2012-01-01

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional $N$-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms are originated in the continual repetition of this non-linear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the co-rotation point. Due to interaction with their host arms, ...

  14. Galaxy And Mass Assembly (GAMA): stellar mass growth of spiral galaxies in the cosmic web

    Science.gov (United States)

    Alpaslan, Mehmet; Grootes, Meiert; Marcum, Pamela M.; Popescu, Cristina; Tuffs, Richard; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J. I.; Davies, Luke J. M.; Driver, Simon P.; Holwerda, Benne W.; Kelvin, Lee S.; Lara-López, Maritza A.; López-Sánchez, Ángel R.; Loveday, Jon; Moffett, Amanda; Taylor, Edward N.; Owers, Matt; Robotham, Aaron S. G.

    2016-04-01

    We look for correlated changes in stellar mass and star formation rate (SFR) along filaments in the cosmic web by examining the stellar masses and UV-derived SFRs of 1799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterize the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher SFRs at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large-scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus suggest a model in which in addition to stellar mass as the primary discriminant, the large-scale environment is imprinted in the SFR as a second-order effect. Furthermore, our detailed results for filament galaxies suggest a model in which gas accretion from voids on to filaments is primarily in an orthogonal direction. Overall, we find our results to be in line with theoretical expectations of the thermodynamic properties of the intergalactic medium in different large-scale environments.

  15. Bars and secular evolution in disk galaxies: Theoretical input

    CERN Document Server

    Athanassoula, E

    2012-01-01

    Bars play a major role in driving the evolution of disk galaxies and in shaping their present properties. They cause angular momentum to be redistributed within the galaxy, emitted mainly from (near-)resonant material at the inner Lindblad resonance of the bar, and absorbed mainly by (near-)resonant material in the spheroid (i.e., the halo and, whenever relevant, the bulge) and in the outer disk. Spheroids delay and slow down the initial growth of the bar they host, but, at the later stages of the evolution, they strengthen the bar by absorbing angular momentum. Increased velocity dispersion in the (near-)resonant regions delays bar formation and leads to less strong bars. When bars form they are vertically thin, but soon their inner parts puff up and form what is commonly known as the boxy/peanut bulge. This gives a complex and interesting shape to the bar which explains a number of observations and also argues that the COBE/DIRBE bar and the Long bar in our Galaxy are, respectively, the thin and the thick p...

  16. VLA HI imaging of the brightest spiral galaxies in Coma

    CERN Document Server

    Bravo-Alfaro, H; Van Gorkom, J H; Balkowski, C

    1999-01-01

    We have obtained 21cm images of 19 spiral galaxies in the Coma cluster, using the VLA in its C and D configurations. The sample selection was based on morphology, brightness, and optical diameters of galaxies within one Abell radius (1.2 degrees). The HI detected, yet deficient galaxies show a strong correlation in their HI properties with projected distance from the cluster center. The most strongly HI deficient (HI Def > 0.4) galaxies are located inside a radius of 30 arcmin (aprox 0.6 Mpc) from the center of Coma, roughly the extent of the central X-ray emission. These central galaxies show clear asymmetries in their HI distribution and/or shifts between the optical and 21cm positions. Seven so called blue disk galaxies in Coma were observed in HI and six were detected. We did a more sensitive search for HI from 11 of the 15 known post starburst galaxies in Coma. None were detected with typical HI mass limits between 3 and 7x10^7 solar masses. Our results present and enhance a picture already familiar for ...

  17. HST detection of spiral structure in two Coma Cluster dwarf galaxies

    CERN Document Server

    Graham, A W; Guzmán, R; Graham, Alister W.; Jerjen, Helmut; Guzman, Rafael

    2003-01-01

    We report the discovery of (stellar) spiral-like structure in Hubble Space Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the Coma cluster. GMP 3629 is the faintest such galaxy detected in a cluster environment, and it is the first such galaxy observed in the dense Coma cluster. The large bulge and the faintness of the broad spiral-like pattern in GMP 3629 suggests that its disk may have been largely depleted. >We may therefore have found an example of the ``missing link'' in theories of galaxy evolution which have predicted that dwarf spiral galaxies, particularly in clusters, evolve into dwarf elliptical galaxies.

  18. Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

    Science.gov (United States)

    Sánchez-Menguiano, L.; Sánchez, S. F.; Pérez, I.; García-Benito, R.; Husemann, B.; Mast, D.; Mendoza, A.; Ruiz-Lara, T.; Ascasibar, Y.; Bland-Hawthorn, J.; Cavichia, O.; Díaz, A. I.; Florido, E.; Galbany, L.; Gónzalez Delgado, R. M.; Kehrig, C.; Marino, R. A.; Márquez, I.; Masegosa, J.; Méndez-Abreu, J.; Mollá, M.; Del Olmo, A.; Pérez, E.; Sánchez-Blázquez, P.; Stanishev, V.; Walcher, C. J.; López-Sánchez, Á. R.; Califa Collaboration

    2016-03-01

    We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3-4 disc effective radii (re). We confirm the results obtained from classical H ii region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 re of αO / H = - 0.075 dex /re with a scatter of σ = 0.016 dex /re when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude, and the presence or absence of bars. In particular, barred galaxies do not seem to display shallower gradients, as predicted by numerical simulations. Interestingly, we find that most of thegalaxies in the sample with reliable oxygen abundance values beyond ~2 effective radii (57 galaxies) present a flattening of the abundance gradient in these outer regions. This flattening is not associated with any morphological feature, which suggests that it is a common property of disc galaxies. Finally, we detect a drop or truncation of the abundance in the inner regions of 27 galaxies in the sample; this is only visible for the most massive galaxies.

  19. IN-SPIRALING CLUMPS IN BLUE COMPACT DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Elmegreen, Bruce G. [IBM Research Division, T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Zhang Hongxin; Hunter, Deidre A., E-mail: bge@watson.ibm.com [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)

    2012-03-10

    Giant star formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the blue compact dwarf (BCD) phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived. The two examples with clumps closest to the center have the largest relative clump masses and the greatest contributions from old stars. An additional indication that the dense central regions of BCDs are like bulges is the high ratio of the inner disk scale height to the scale length, which is comparable to 1 for four of the galaxies.

  20. The ultraviolet attenuation law in backlit spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Keel, William C. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Manning, Anna M. [Stennis Space Center, MS 39522 (United States); Holwerda, Benne W. [ESA-ESTEC, Keplerlaan 1, 2201-AZ Noordwijk (Netherlands); Lintott, Chris J. [Astrophysics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin, E-mail: wkeel@ua.edu, E-mail: ammanning@bama.ua.edu, E-mail: bholwerd@rssd.esa.int, E-mail: Twitter@BenneHolwerda, E-mail: cjl@astro.ox.ac.uk, E-mail: Twitter@chrislintott, E-mail: kevin.schawinski@phys.ethz.ch, E-mail: Twitter@kevinschawinski [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly 'gray' law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that

  1. The ultraviolet attenuation law in backlit spiral galaxies

    International Nuclear Information System (INIS)

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly 'gray' law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that

  2. Discovery of rare double-lobe radio galaxies hosted in spiral galaxies

    CERN Document Server

    Singh, Veeresh; Sievers, Jonathan; Wadadekar, Yogesh; Hilton, Matt; Beelen, Alexandre

    2015-01-01

    Double-lobe radio galaxies in the local Universe have traditionally been found to be hosted in elliptical or lenticular galaxies. We report the discovery of four spiral-host double-lobe radio galaxies (J0836+0532, J1159+5820, J1352+3126 and J1649+2635) that are discovered by cross-matching a large sample of 187005 spiral galaxies from SDSS DR7 to the full catalogues of FIRST and NVSS. J0836+0532 is reported for the first time. The host galaxies are forming stars at an average rate of 1.7 $-$ 10 M$_{\\odot}$ yr$^{-1}$ and possess Super Massive Black Holes (SMBHs) with masses of a few times 10$^{8}$ M$_{\\odot}$. Their radio morphologies are similar to FR-II radio galaxies with total projected linear sizes ranging from 86 kpc to 420 kpc, but their total 1.4 GHz radio luminosities are only in the range 10$^{24}$ $-$ 10$^{25}$ W Hz$^{-1}$. We propose that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions, mergers, and the...

  3. Galaxy And Mass Assembly (GAMA): Stellar mass growth of spiral galaxies in the cosmic web

    CERN Document Server

    Alpaslan, Mehmet; Marcum, Pamela M; Popescu, Cristina; Tuffs, Richard; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J I; Davies, Luke J M; Driver, Simon P; Holwerda, Benne W; Kelvin, Lee S; Lara-López, Maritza A; López-Sánchez, Ángel R; Loveday, Jon; Moffett, Amanda; Taylor, Edward N; Owers, Matt; Robotham, Aaron S G

    2016-01-01

    We look for correlated changes in stellar mass and star formation rate along filaments in the cosmic web by examining the stellar masses and UV-derived star formation rates (SFR) of 1,799 ungrouped and unpaired spiral galaxies that reside in filaments. We devise multiple distance metrics to characterise the complex geometry of filaments, and find that galaxies closer to the cylindrical centre of a filament have higher stellar masses than their counterparts near the periphery of filaments, on the edges of voids. In addition, these peripheral spiral galaxies have higher specific star formation rates (SSFR) at a given mass. Complementing our sample of filament spiral galaxies with spiral galaxies in tendrils and voids, we find that the average SFR of these objects in different large scale environments are similar to each other with the primary discriminant in SFR being stellar mass, in line with previous works. However, the distributions of SFRs are found to vary with large-scale environment. Our results thus su...

  4. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    CERN Document Server

    Ziegler, Bodo L; Da Rocha, Cristiano; Böhm, Asmus; Peletier, Reynier F; Verdugo, Miguel

    2009-01-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, position angle and ellipticity. Combining the spectra of three slit positions per galaxy using the MXU mode of VLT/FORS2 we construct the two-dimensional velocity field from gas emission lines for 16 cluster members and 33 field galaxies. The kinematic position angle and flatness are derived by a Fourier expansion of elliptical velocity profiles. To trace possible interaction processes, we define three irregularity indicators based on an identical analysis of local galaxies from the SINGS project. Our distant sample display...

  5. Dynamical effect of gas on spiral pattern speed in galaxies

    CERN Document Server

    Ghosh, Soumavo

    2016-01-01

    In the density wave theory of spiral structure, the grand-design two-armed spiral pattern is taken to rotate rigidly in a galactic disc with a constant, definite pattern speed. The observational measurement of the pattern speed of the spiral arms, though difficult, has been achieved in a few galaxies such as NGC 6946, NGC 2997, and M 51 which we consider here. We examine whether the theoretical dispersion relation permits a real solution for wavenumber corresponding to a stable wave, for the observed rotation curve and the pattern speed values. We find that the disc when treated to consist of stars alone, as is usually done in literature, does not generally support a stable density wave for the observed pattern speed. Instead the inclusion of the low velocity dispersion component, namely, gas, is essential to obtain a stable density wave. Further, we obtain a theoretical range of allowed pattern speeds that correspond to a stable density wave at a certain radius, and check that for the three galaxies consider...

  6. Chemical abundances from planetary nebulae in local spiral galaxies

    CERN Document Server

    Richer, M G

    2015-01-01

    While the chemical abudances observed in bright planetary nebulae in local spiral galaxies are less varied than their counterparts in dwarfs, they provide new insight. Their helium abundances are typically enriched by less than 50\\% compared to the primordial abundance. Nitrogen abundances always show some level of secondary enrichment, but the absolute enrichment is not extreme. In particular, type I PNe are rare among the bright PNe in local spirals. The oxygen and neon abundances are very well correlated and follow the relation between these abundances observed in star-forming galaxies, implying that either the progenitor stars of these PNe modify neither abundance substantially or that they modify both to maintain the ratio (not predicted by theory). According to theory, these results imply that the progenitor stars of bright PNe in local spirals have masses of about $2\\,\\mathrm M_{\\odot}$ or less. If so, the progenitors of these PNe have substantial lifetimes that allow us to use them to study the recent...

  7. The mass function of young star clusters in spiral galaxies

    CERN Document Server

    Larsen, S S

    2008-01-01

    The initial cluster mass function (ICMF) in spiral galaxy discs is constrained and compared with data for old globular clusters and young clusters in starbursts. It is found that the observed ages and luminosities of the brightest clusters in spiral discs can be reproduced if the ICMF is a Schechter function with a cut-off mass (Mc) of a few times 10^5 Msun and disruption of optically visible clusters is dominated by relatively slow secular evolution. A direct Schechter function fit to the combined cluster MF for all spirals in the sample studied here yields Mc = (2.1+/-0.4)x10^5 Msun. The MFs in cluster-poor and cluster-rich spirals are statistically indistinguishable. An Mc=2.1x10^5 Msun Schechter function also fits the MF of young clusters in the Large Magellanic Cloud. If the same ICMF applies in the Milky Way, a bound cluster with M>10^5 Msun will form about once every 10 Myr, while an M>10^6 Msun cluster will form only once every 50 Gyr. Luminosity functions (LFs) of model cluster populations drawn from...

  8. Halpha Kinematics of S4G Spiral Galaxies - III. Inner rotation curves

    CERN Document Server

    Erroz-Ferrer, Santiago; Leaman, Ryan; Dıaz-Garcia, Simon; Salo, Heikki; Laurikainen, Eija; Querejeta, Miguel; Muñoz-Mateos, Juan Carlos; Athanassoula, E; Bosma, Albert; Comeron, Sebastien; Elmegreen, Bruce G; Martınez-Valpuesta, Inma

    2016-01-01

    We present a detailed study of the shape of the innermost part of the rotation curves of a sample of 29 nearby spiral galaxies, based on high angular and spectral resolution kinematic Halpha Fabry-Perot observations. In particular, we quantify the steepness of the rotation curve by measuring its slope dRvc(0). We explore the relationship between the inner slope and several galaxy parameters, such as stellar mass, maximum rotational velocity, central surface brightness ({\\mu}0), bar strength and bulge-to-total ratio. Even with our limited dynamical range, we find a trend for low-mass galaxies to exhibit shallower rotation curve inner slopes than high-mass galaxies, whereas steep inner slopes are found exclusively in high-mass galaxies. This trend may arise from the relationship between the total stellar mass and the mass of the bulge, which are correlated among them. We find a correlation between the inner slope of the rotation curve and the morphological T-type, complementary to the scaling relation between d...

  9. TWO-DIMENSIONAL KINEMATICS OF THE EDGE-ON SPIRAL GALAXY ESO 379-006

    Energy Technology Data Exchange (ETDEWEB)

    Rosado, M.; Gabbasov, R. F.; Repetto, P.; Martos, M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-264, CP 04510 Mexico, D. F. (Mexico); Fuentes-Carrera, I. [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional, U. P. Adolfo Lopez Mateos, Zacatenco, 07730 Mexico, D. F. (Mexico); Amram, P.; Hernandez, O. [Laboratoire d' Astrophysique de Marseille, Aix-Marseille University (France); CNRS, 38 rue Frederic Joliot-Curie, 13338 Marseille Cedex 13 (France)

    2013-05-15

    We present a kinematical study of the nearly edge-on galaxy ESO 379-006 that shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy at H{alpha}, we study the kinematics of ESO 379-006 using velocity maps and position-velocity diagrams parallel to the major and to the minor axis of the galaxy. We build the rotation curve of the disk and discuss the role of projection effects due to the fact of viewing this galaxy nearly edge-on. The twisting of the isovelocities in the radial velocity field of the disk of ESO 379-006 as well as the kinematical asymmetries found in some position-velocity diagrams parallel to the minor axis of the galaxy suggest the existence of deviations to circular motions in the disk that can be modeled and explained with the inclusion of a radial inflow probably generated by a bar or by spiral arms. We succeeded in detecting extraplanar diffuse ionized gas in this galaxy. At the same time, from the analysis of position-velocity diagrams, we found some evidence that the extraplanar gas could lag in rotation velocity with respect to the midplane rotation.

  10. Gas velocity patterns in simulated galaxies: Observational diagnostics of spiral structure theories

    CERN Document Server

    Baba, Junichi; Miyamoto, Yusuke; Egusa, Fumi; Kuno, Nario

    2016-01-01

    There are two theories of stellar spiral arms in isolated disc galaxies that model stellar spiral arms with different longevities: quasi-stationary density wave theory, which characterises spirals as rigidly rotating, long-lived patterns (i.e. steady spirals), and dynamic spiral theory, which characterises spirals as differentially rotating, transient, recurrent patterns (i.e. dynamic spirals). In order to discriminate between these two spiral models observationally, we investigated the differences between the gas velocity patterns predicted by these two spiral models in hydrodynamic simulations. We found that the azimuthal phases of the velocity patterns relative to the gas density peaks (i.e. gaseous arms) differ between the two models, as do the gas flows; nevertheless, the velocity patterns themselves are similar for both models. Such similarity suggests that the mere existence of streaming motions does not conclusively confirm the steady spiral model. However, we found that the steady spiral model shows ...

  11. Kinematic properties of double-barred galaxies: simulations vs. integral-field observations

    CERN Document Server

    Du, Min; Shen, Juntai; Cappellari, Michele

    2016-01-01

    Using high resolution $N$-body simulations, we recently reported that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady double-barred (S2B) structure. Here we study the kinematics of these S2B simulations, and compare them to integral-field observations from ATLAS$^{3D}$ and SAURON. We show that S2B galaxies exhibit several distinct kinematic features, namely: (1) significantly distorted isovelocity contours at the transition region between the two bars, (2) peaks in $\\sigma_\\mathrm{LOS}$ along the minor axis of inner bars, which we term "$\\sigma$-humps", that are often accompanied by ring/spiral-like features of increased $\\sigma_\\mathrm{LOS}$, (3) $h_3-\\bar{v}$ anti-correlations in the region of the inner bar for certain orientations, and (4) rings of positive $h_4$ when viewed at low inclinations. The most impressive of these features are the $\\sigma$-humps, these evolve with the inner bar, oscillating in strength just as the inner bar does as it rotates relative...

  12. In-spiraling Clumps in Blue Compact Dwarf Galaxies

    CERN Document Server

    Elmegreen, Bruce G; Hunter, Deidre

    2012-01-01

    Giant star-formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the BCD phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived....

  13. Analysis of the Spiral Properties in Prototype Galaxies

    Science.gov (United States)

    Russell, William Stuart

    Numerical methods and algorithms are developed for analyzing the distribution of pitch angles of global and local spiral structure in disk-shaped galaxies. From the distribution of gas clouds and young stellar associations, "partitioning" methods based on nearest neighbor and Voronoi polyhedra calculations are applied to capture regions of high population density associated with local arm segments, spurs, feathers and secondary features. The pitch angle and length of each of these features are determined using least squares procedures applied in logarithmic spiral coordinates. The spectrum of pitch angles for both prototype and observed galaxies is analyzed and discussed. The evolution of prominent secondary features is examined over a 40 Myr period and characteristic behavior is interpreted in terms of competing mechanisms such as differential rotation and the gravitational force field induced by nearby features. A refined numerical method is also presented for modeling the self-gravity force field arising in prototype galaxy simulations. The loss of resolution from previous methods is compared to results obtained using high order finite differencing and modified bicubic interpolation. ftn*This work was supported in part under W. W. Roberts' grants from the National Science Foundation (Grant AST-87-12084) and NASA (Grant NAGW-929). The computational work was carried out on the CDC 855 and the AMSUN 3/260 cluster at the University of Virginia and the CRAY Y-MP at the Pittsburgh Superconducting Center (Grant AST880019P: W. W. Roberts, P.I.).

  14. Bar pattern speeds in CALIFA galaxies: I. Fast bars across the Hubble sequence

    CERN Document Server

    Aguerri, J A L; Falcón-Barroso, J; Amorin, A; Barrera-Ballesteros, J; Fernandes, R Cid; García-Benito, R; García-Lorenzo, B; Delgado, R M González; Husemann, B; Kalinova, V; Lyubenova, M; Marino, R A; Márquez, I; Mast, D; Pérez, E; Sánchez, S F; van de Ven, G; Walcher, C J; Backsmann, N; Cortijo-Ferrero, C; Bland-Hawthorn, J; del Olmo, A; Iglesias-Páramo, J; Pérez, I; Sánchez-Blázquez, P; Wisotzki, L; Ziegler, B

    2015-01-01

    The bar pattern speed ($\\Omega_{\\rm b}$) is defined as the rotational frequency of the bar, and it determines the bar dynamics. Several methods have been proposed for measuring $\\Omega_{\\rm b}$. The non-parametric method proposed by Tremaine \\& Weinberg (1984; TW) and based on stellar kinematics is the most accurate. This method has been applied so far to 17 galaxies, most of them SB0 and SBa types. We have applied the TW method to a new sample of 15 strong and bright barred galaxies, spanning a wide range of morphological types from SB0 to SBbc. Combining our analysis with previous studies, we investigate 32 barred galaxies with their pattern speed measured by the TW method. The resulting total sample of barred galaxies allows us to study the dependence of $\\Omega_{\\rm b}$ on galaxy properties, such as the Hubble type. We measured $\\Omega_{\\rm b}$ using the TW method on the stellar velocity maps provided by the integral-field spectroscopy data from the CALIFA survey. Integral-field data solve the problem...

  15. Galaxy Zoo and ALFALFA: Atomic Gas and the Regulation of Star Formation in Barred Disc Galaxies

    CERN Document Server

    Masters, Karen L; Haynes, Martha P; Keel, William C; Lintott, Chris; Simmons, Brooke; Skibba, Ramin; Bamford, Steven; Giovanelli, Riccardo; Schawinski, Kevin

    2012-01-01

    We study the observed correlation between atomic gas content and the likelihood of hosting a large scale bar in a sample of 2090 disc galaxies. Such a test has never been done before on this scale. We use data on morphologies from the Galaxy Zoo project and information on the galaxies' HI content from the ALFALFA blind HI survey. Our main result is that the bar fraction is significantly lower among gas rich disc galaxies than gas poor ones. This is not explained by known trends for more massive (stellar) and redder disc galaxies to host more bars and have lower gas fractions: we still see at fixed stellar mass a residual correlation between gas content and bar fraction. We discuss three possible causal explanations: (1) bars in disc galaxies cause atomic gas to be used up more quickly, (2) increasing the atomic gas content in a disc galaxy inhibits bar formation, and (3) bar fraction and gas content are both driven by correlation with environmental effects (e.g. tidal triggering of bars, combined with strangu...

  16. Fundamental mass-spin-morphology relation of spiral galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Obreschkow, D. [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Glazebrook, K. [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) (Australia)

    2014-03-20

    This work presents high-precision measurements of the specific baryon angular momentum j {sub b} contained in stars, atomic gas, and molecular gas, out to ≳ 10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by an order of magnitude, leading to the discovery of a strong correlation between the baryon mass M {sub b}, j {sub b}, and the bulge mass fraction β, fitted by β=−(0.34±0.03) lg (j{sub b}M{sub b}{sup −1}/[10{sup −7} kpc km s{sup −1} M{sub ⊙}{sup −1}])−(0.04±0.01) on the full sample range of 0 ≤ β ≲ 0.3 and 10{sup 9} M {sub ☉} < M {sub b} < 10{sup 11} M {sub ☉}. The corresponding relation for the stellar quantities M {sub *} and j {sub *} is identical within the uncertainties. These M-j-β relations likely originate from the proportionality between jM {sup –1} and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a cold dark matter model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relation, in terms of the M-j(-β) relation. These results advocate the use of mass and angular momentum as the most fundamental quantities of spiral galaxies.

  17. Star Clusters in Pseudo-Bulges of Spiral Galaxies

    CERN Document Server

    Di Nino, Daiana; Stiavelli, Massimo; Carollo, C Marcella; Scarlata, Claudia; Wyse, Rosemary F G

    2009-01-01

    We present a study of the properties of the star-cluster systems around pseudo-bulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 to 37 Mpc. Star clusters are identified from multiband HST ACS and WFPC2 imaging data by combining detections in 3 bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthesis models to infer the masses and ages of the star clusters. Photometric errors and completeness are estimated by means of artificial source Monte Carlo simulations. Dust extinction is estimated by considering F160W NICMOS observations of the central regions of the galaxies, augmenting our wavelength coverage. In all galaxies we identify star clusters with a wide range of ages, from young (age 100-250 Myr), more massive, red clusters. Some of the latter might likely evolve into objects similar to the Milky Way's globular clusters. We compute the specific frequencies for the older clusters with respect to the galaxy an...

  18. HI power spectrum of the spiral galaxy NGC628

    CERN Document Server

    Dutta, Prasun; Bharadwaj, Somnath; Chengalur, Jayaram N

    2007-01-01

    We have measured the HI power spectrum of the nearly face-on spiral galaxy NGC628 (M74) using a visibility based estimator. The power spectrum is well fitted by a power law $P(U)=AU^{\\alpha}$, with $\\alpha =- 1.6\\pm0.2$ over the length scale $800 {\\rm pc} {\\rm to} 8 {\\rm kpc}$. The slope is found to be independent of the width of the velocity channel. This value of the slope is a little more than one in excess of what has been seen at considerably smaller length scales in the Milky-Way, Small Magellanic Cloud (LMC), Large Magellanic Cloud (SMC) and the dwarf galaxy DDO210. We interpret this difference as indicating a transition from three dimensional turbulence at small scales to two dimensional turbulence in the plane of the galaxy's disk at length scales larger than galaxy's HI scale height. The slope measured here is similar to that found at large scales in the LMC. Our analysis also places an upper limit to the galaxy's scale height at $800\\ {\\rm pc}$ .

  19. The emissivity of dust grains in spiral galaxies

    OpenAIRE

    Alton, P. B.; Xilouris, E. M.; Misiriotis, A.; Dasyra, K. M.; Dumke, M.

    2004-01-01

    We use the radiation transfer simulation of Xilouris et al. (1999) to constrain the quantity of dust in three nearby spiral galaxies (NGC 4013, NGC 5907 and NGC 4565). The predicted visual optical depth from the model is compared with the thermal continuum radiation detected from NGC 4013 and NGC 5907 at 850 microns and from NGC 4565 at 1.2 mm. The former is based on SCUBA images of NGC 4013 and NGC 5907, reduced and presented for the first time in this work. The comparison of visual optical ...

  20. Iron emission line from the spiral galaxy M101

    CERN Document Server

    Yamauchi, Shigeo

    2015-01-01

    Archival Suzaku data of the face-on spiral galaxy M101 were analyzed. An intense emission line at 6.72^{+0.10}_{-0.12} keV was detected in the central region. This line is identified with a K-line from He-like iron, which indicates the existence of a thin thermal plasma with a temperature of several keV. The iron line luminosity within the central 5 arcmin radius region is estimated to be (2-12)x10^{37} erg s^{-1}. The origin of the iron emission line is discussed.

  1. Cosmic evolution of bars in simulations of galaxy formation

    CERN Document Server

    Okamoto, Takashi; Habe, Asao

    2014-01-01

    We investigate the evolution of two bars formed in fully self-consistent hydrodynamical simulations of the formation of Milky Way-mass galaxies. One galaxy shows higher central mass concentration and has a longer and stronger bar than the other at $z = 0$. The stronger bar evolves by transferring its angular momentum mainly to the dark halo. Consequently the rotation speed of the bar decreases with time, while the amplitude of the bar increases with time. While these features qualitatively agree with the results obtained by idealized simulations, our bars show some unusual behaviors. The pattern speed of the stronger bar largely goes up and down within a half revolution in its early evolutionary stage. This unsteady rotation occurs when the bar is misaligned with the $m = 4$ mode Fourier component. The amplitude of the weaker bar does not increase despite the fact that its rotation slows down with time. This result contradicts what is expected from idealized simulations and is caused by the decline of the cen...

  2. Image Decomposition of Barred Galaxies and AGN Hosts

    CERN Document Server

    Gadotti, Dimitri Alexei

    2007-01-01

    I present the results of multi-component decomposition of V and R broadband images of a sample of 17 nearby galaxies. I use BUDDA v2.1 to produce the fits, allowing to include bars and AGN in the models. A comparison with previous results from the literature shows good agreement. It is found that the axial ratio of bars, as measured from ellipse fits, can be severely underestimated if the galaxy axisymmetric component is relatively luminous. Thus, reliable bar axial ratios can only be determined by taking into account the contributions of bulge and disc to the light distribution in the galaxy image. Through a number of tests, I show that neglecting bars when modelling barred galaxies can result in a overestimation of the bulge-to-total luminosity ratio of a factor of two. Similar effects result when bright, type 1 AGN are not considered in the models. By artificially redshifting the images, I show that the structural parameters of more distant galaxies can in general be reliably retrieved through image fittin...

  3. Orbital Support of Fast and Slow Inner Bars in Double Barred Galaxies

    CERN Document Server

    Maciejewski, Witold

    2010-01-01

    We analyze how the orbital support of the inner bar in a double-barred galaxy (nested bars) depends on the angular velocity (i.e. pattern speed) of this bar. We study orbits in seven models of double bars using the method of invariant loops. The range of pattern speed is covered exhaustively. We find that not all pattern speeds are allowed when the inner bar rotates in the same direction as the outer bar. Below a certain minimum pattern speed orbital support for the inner bar abruptly disappears, while at high values of this speed the orbits indicate an increasingly round bar that looks more like a twist in the nuclear isophotes than a dynamically independent component. For values between these two extremes, orbits supporting the inner bar extend further out as the bar's pattern speed decreases, their corresponding loops become more eccentric, pulsate more, and their rotation becomes increasingly non-uniform, as they speed up and slow down in their motion. Lower pattern speeds also lead to a less coherent bar...

  4. The Evidence for Massive Star Formation in Early-Type Spiral Galaxies

    CERN Document Server

    Hameed, S A; Hameed, Salman; Devereux, Nick

    1997-01-01

    A recent analysis of the IRAS database indicates that the massive star formation rates in early-type (Sa-Sab) spirals are comparable to the massive star formation rates in late-type spirals. $H\\alpha$ imaging of some of the infrared luminous early-type spirals reveals two types of galaxies. One type shows clear signs of interaction, whereas the other type appears to host a nuclear starburst. The occurence of nuclear starbursts in early-type spirals may be related to the propensity for such galaxies to also host Seyfert nuclei. The evidence for interactions suggests that early-type spirals are evolving in the current epoch.

  5. The Luminous Convolution Model for spiral galaxy rotation curves

    CERN Document Server

    Cisneros, S; Oblath, N S; Formaggio, J A

    2015-01-01

    The Luminous Convolution Model (LCM) is an empirical formula, based on a heuristic convolution of Relativistic transformations, which makes it possible to predict the observed rotation curves of a broad class of spiral galaxies from luminous matter alone. Since the LCM is independent of distance estimates or dark matter halo densities, it is the first model of its kind which constrains luminous matter modeling directly from the observed spectral shifts of characteristic photon emission/absorption lines. In this paper we present the LCM solution to a diverse sample of twenty-five (25) galaxies of varying morphologies and sizes. For the chosen sample, it is shown that the LCM is more accurate than either Modified Newtonian Dynamics or dark matter models and returns physically reasonable mass to light ratios and exponential scale lengths. Unlike either Modified Newtonian Dynamics or dark matter models, the LCM predicts something which is directly falsifiable through improvements in our observational capacity, th...

  6. Which bulges are favoured by barred S0 galaxies?

    CERN Document Server

    Barway, Sudhanshu; Vaghmare, Kaustubh; Kembhavi, Ajit K

    2016-01-01

    S0 galaxies are known to host classical bulges with a broad range of size and mass, while some such S0s are barred and some not. The origin of the bars has remained as a long-standing problem -- what made bar formation possible in certain S0s? By analysing a large sample of S0s with classical bulges observed by the Spitzer space telescope, we find that most of our barred S0s host comparatively low-mass classical bulges, typically with bulge-to-total ratio ($B/T$) less than $0.5$; whereas S0s with more massive classical bulges than these do not host any bar. Furthermore, we find that amongst the barred S0s, there is a trend for the longer and massive bars to be associated with comparatively bigger and massive classical bulges -- possibly suggesting bar growth being facilitated by these classical bulges. In addition, we find that the bulge effective radius is always less than the bar effective radius --indicating an interesting synergy between the host classical bulge and bars being maintained while bar growth ...

  7. Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

    NARCIS (Netherlands)

    Mora, M.D.; Larsen, S.S.; Kissler-Patig, M.

    2008-01-01

    Context. Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. Aims. Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (1

  8. Automated bar detection in local disc galaxies from the SDSS - The colors of bars

    CERN Document Server

    Consolandi, Guido

    2016-01-01

    This paper describes an automatic isophotal fitting procedure that succeeds, without the support of any visual inspection of neither the images nor the ellipticity/P.A. radial profiles, at extracting a fairly pure sample of barred LTGs among thousands of optical images from the SDSS. The procedure relies on the methods described in Consolandi et al. (2016) to robustly extract the photometrical properties of a large sample of local SDSS galaxies and is tailored to extract bars on the basis of their well-known peculiarities in their P.A. and ellipticity profiles. It has been run on a sample of 5853 galaxies in the Coma and Local supercluster. The procedure extracted for each galaxy a color, an ellipticity and a position angle radial profile of the ellipses fitted to the isophotes. Examining automatically the profiles of 922 face-on late-type galaxies (B/A >0.7) the procedure found that ~ 36 % are barred. The local bar fraction strongly increases with stellar mass. The sample of barred galaxies is used to constr...

  9. Spirality: A Novel Way to Measure Spiral Arm Pitch Angle

    CERN Document Server

    Shields, Douglas W; Pfountz, Casey; Davis, Benjamin L; Hartley, Matthew; Imani, Hamed Pour; Slade, Zac; Kennefick, Daniel; Kennefick, Julia

    2015-01-01

    We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 minutes per galaxy, assuming at least 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code's results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies defined by DMS PPak. Spirality's error bars overlapped 2DFFT's error bars for 26 of the 30 galaxies. The two methods' agreement correlates strongly with galaxy radius in pixels and also with i-band magnitude, but not with redshift, a result that is consistent with at least some galaxies' spiral structure being fully formed by z=1.2, beyond which there are few galaxies in our sample. The Spirality code pa...

  10. Particle Paths of Lagrangian Velocity Distribution Simulating the Spiral Arms of Galaxy M51

    Institute of Scientific and Technical Information of China (English)

    Tzu-Fang Chen; Georgios H. Vatistas; Sui Lin

    2008-01-01

    Galaxies are huge families of stars held together by their own gravities. The system M51 is a spiral galaxy. It possesses billions of stars. The range of the spiral arms extends hundred thousand light years. The present study is in an attempt in using the particle paths of the Lagrangian flow field to simulate the spiral arms of Galaxy M51.The Lagrangian flow field is introduced. The initial locations of fluid particles in the space between two concentric cylinders are first specified. Then a linear velocity distribution of the fluid particles is used with different angle rotations of the particles to obtain the particle paths in the Lagrangian diagram. For simulating the spiral arms of Galaxy M51, the Lagrangian M51 diagram is developed. The particle paths of the Lagrangian M51 diagram agree quite well with the spiral arms of Galaxy M51.

  11. Star formation in the warped outer pseudoring of the spiral galaxy NGC 3642

    CERN Document Server

    Verdes-Montenegro, L; Athanassoula, E

    2002-01-01

    NGC 3642 was classified as a spiral galaxy with three rings and no bar. We have performed an HI and optical study of this nearly face-on galaxy. We find that the nuclear ring might in fact be part of an inner one-armed spiral, that could be driving nuclear accretion and feeding the central activity in the inner kpc. The inner ring is faint, and the outer ring is a rather ill-defined pseudoring. Furthermore, the size ratio of the rings is such that they cannot be due to a single pattern speed linking them together. The outer pseudoring is peculiar, since it lies in the faint outer parts of the disk, where star formation is still going on at 1.4 times the optical radius. Higher HI column densities are associated with these regions and the atomic gas layer is warped. These perturbations affect only the outer disk, since the kinematics within the main body conforms well to an ordinary differentially rotating disk. We propose here that both nuclear activity and star formation in the warped outer parts might be lin...

  12. Probing the stellar populations in the outskirts of spiral galaxies

    International Nuclear Information System (INIS)

    We present our results on the stellar population properties of the outskirts of disk galaxies. In particular, we focus on spiral galaxies with stellar disk truncations in their radial surface brightness profiles. Using SDSS data we show color gradients. We find that the color radial profile exhibits a 'U'-shape', showing a minimum at the position of the break of the surface brightness profile. We obtain stellar surface mass density profiles of truncated galaxies as well, these show a peculiar behaviour: they follow very closely an exponential decrement. This suggests the idea that the observed properties of truncated galaxies are not caused by a drop in the mass distribution but by a different stellar population in the outer regions of the disks. Confronting this with current theoretical scenarios we find that this is likely to be a result of secular evolution, in which scenario stars are being formed inside the break and then being motioned outwards which would result in an inverted age gradient corresponding to the observed color profiles. Having maintained this idea, using multiwave-length data from GALEX, SDSS, UKIDSS and SPITZER we showed a dependence of the inner-outer scale-length ratio of truncated disks. Our results suggest that there is an existing general trend of the scale-length ratio: from bluer to redder bands the scale-length ratio decreases, which is in accordance with the stellar disk being dominated by an older stellar population in the outer disk.

  13. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    CERN Document Server

    Watkins, Aaron E; Harding, Paul

    2016-01-01

    We present results from deep, wide-field surface photometry of three nearby (D=4--7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches limiting surface brightnesses of $\\mu_{B} \\sim$ 28 -- 30 mag arcsec$^{-2}$ and probes colors down to $\\mu_{B} \\sim$ 27.5 mag arcsec$^{-2}$. We compare our broadband optical data to available ultraviolet and high column-density HI data to better constrain the star forming history and stellar populations of the outermost parts of each galaxy's disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies' outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarit...

  14. The BaLROG project - I. Quantifying the influence of bars on the kinematics of nearby galaxies

    CERN Document Server

    Seidel, M K; Martínez-Valpuesta, I; Díaz-García, S; Laurikainen, E; Salo, H; Knapen, J H

    2015-01-01

    We present the BaLROG (Bars in Low Redshift Optical Galaxies) sample of 16 morphologically distinct barred spirals to characterise observationally the influence of bars on nearby galaxies. Each galaxy is a mosaic of several pointings observed with the IFU spectrograph SAURON leading to a tenfold sharper spatial resolution (~100 pc) compared to ongoing IFU surveys. In this paper we focus on the kinematic properties. We calculate the bar strength Qb from classical torque analysis using 3.6 {\\mu}m Spitzer (S4G) images, but also develop a new method based solely on the kinematics. A correlation between the two measurements is found and backed up by N-body simulations, verifying the measurement of Qb . We find that bar strengths from ionised gas kinematics are ~2.5 larger than those measured from stellar kinematics and that stronger bars have enhanced influence on inner kinematic features. We detect that stellar angular momentum "dips" at 0.2$\\pm$0.1 bar lengths and half of our sample exhibits an anti-correlation ...

  15. Two-dimensional spectroscopy of double-barred galaxies

    OpenAIRE

    A. V. Moiseev

    2002-01-01

    We describe the results of our spectroscopy for a sample of barred galaxies whose inner regions exhibit an isophotal twist commonly called a secondary bar. The line-of-sight velocity fields of the ionized gas and stars and the light-of-sight velocity dispersion fields of the stars were constructed from two-dimensional spectroscopy with the 6m Special Astrophysical Observatory telescope. We detected various types of non-circular motions of ionized gas: radial flows within large-scale bars, cou...

  16. A SINFONI view of circum-nuclear star-forming rings in spiral galaxies

    CERN Document Server

    Falcón-Barroso, J; Schinnerer, E; Knapen, J H; Ryder, S

    2007-01-01

    We present near-infrared (H- and K-band) SINFONI integral-field observations of the circumnuclear star formation rings in five nearby spiral galaxies. We made use of the relative intensities of different emission lines (i.e. [FeII], HeI, Brg) to age date the stellar clusters present along the rings. This qualitative, yet robust, method allows us to discriminate between two distinct scenarios that describe how star formation progresses along the rings. Our findings favour a model where star formation is triggered predominantly at the intersection between the bar major axis and the inner Lindblad resonance and then passively evolves as the clusters rotate around the ring ('Pearls on a string' scenario), although models of stochastically distributed star formation ('Popcorn' model) cannot be completely ruled out.

  17. Gas flow and dark matter in the inner parts of early-type barred galaxies - I. SPH simulations and comparison with the observed kinematics

    NARCIS (Netherlands)

    Perez, [No Value; Fux, R; Freeman, K

    2004-01-01

    This paper presents the dynamical simulations run in the potential derived from the light distribution of 5 late-type barred spiral galaxies (IC 5186, NGC 5728, NGC 7267, NGC 7483 and NGC 5505). The aim is to determine whether the mass distribution together with the hydrodynamical simulations can re

  18. Gas Dynamics and Outflow in the Barred Starburst Galaxy NGC 1808 Revealed with ALMA

    Science.gov (United States)

    Salak, Dragan; Nakai, Naomasa; Hatakeyama, Takuya; Miyamoto, Yusuke

    2016-05-01

    NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear region. To study the inflow and outflow processes related to star formation and dynamical evolution of the galaxy, we have carried out 12CO (J=1-0) mapping observations of the central r ∼ 4 kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array. Four distinct components of molecular gas are revealed at high spatial resolution of 2″ (∼100 pc): (1) a compact (r < 200 pc) circumnuclear disk (CND), (2) r ∼ 500 pc ring, (3) gas-rich galactic bar, and (4) spiral arms. Basic geometric and kinematic parameters are derived for the central 1 kpc region using tilted-ring modeling. The derived rotation curve reveals multiple mass components that include (1) a stellar bulge, (2) a nuclear bar and molecular CND, and (3) an unresolved massive (∼107 M ⊙) core. Two systemic velocities, 998 km s‑1 for the CND and 964 km s‑1 for the 500 pc ring, are revealed, indicating a kinematic offset. The pattern speed of the primary bar, derived by using a cloud-orbit model, is 56 ± 11 km s‑1 kpc‑1. Noncircular motions are detected associated with a nuclear spiral pattern and outflow in the central 1 kpc region. The ratio of the mass outflow rate to the star formation rate is {\\dot{M}}{out}/{SFR}∼ 0.2 in the case of optically thin CO (1–0) emission in the outflow, suggesting low efficiency of star formation quenching.

  19. The Void in the Sculptor Group Spiral Galaxy NGC 247

    CERN Document Server

    Wagner-Kaiser, R; Sarajedini, A; Chakrabarti, S

    2014-01-01

    The dwarf galaxy NGC 247, located in the Sculptor Filament, displays an apparent void on the north side of its spiral disk. The existence of the void in the disk of this dwarf galaxy has been known for some time, but the exact nature and cause of this strange feature has remained unclear. We investigate the properties of the void in the disk of NGC 247 using photometry of archival Hubble Space Telescope data to analyze the stars in and around this region. Based on a grid of isochrones from log(t)=6.8 to log(t)=10.0, we assign ages using nearest-neighbor interpolation. Examination of the spatial variation of these ages across the galaxy reveals an age difference between stars located inside the void region and stars located outside this region. We speculate that the void in NGC 247's stellar disk may be due to a recent interaction with a nearly dark sub-halo that collided with the disk and could account for the long-lived nature of the void.

  20. The Luminosity Function of Star Clusters in Spiral Galaxies

    CERN Document Server

    Larsen, S S

    2002-01-01

    Star clusters in 6 nearby spiral galaxies are examined using archive images from HST/WFPC2. The galaxies have previously been studied from the ground and some of them are known to possess rich populations of "young massive clusters" (YMCs). Comparison with the HST images indicates a success-rate of about 75% for the ground-based cluster detections, with typical contaminants being blends or loose groupings of several stars in crowded regions. The luminosity functions (LFs) of cluster candidates identified on the HST images are analyzed and compared with existing data for the Milky Way and the LMC. The LFs are well approximated by power-laws of the form dN(L)/dL ~ L^alpha, with slopes in the range -2.4galaxies. The surface density of star clusters at a reference magnitude of M(V)=-8 scales with the me...

  1. On the nature of the barlens component in barred galaxies

    CERN Document Server

    Athanassoula, E; Salo, H; Bosma, A

    2014-01-01

    Barred galaxies have very interesting morphological features. Here we examine the barlens, a lens-like component whose extent along the bar major axis is shorter than that of the bar and whose outline is oval or circular. We show that such a component can also be found in a number of N-body plus SPH simulations. We analyse its properties by converting simulation snapshots into images, which we then analyse in the same way as images of observed galaxies. We make extensive comparisons with galaxies from the NIRS0S (Near Infrared S0 Survey) and the S$^4$G (Spitzer Stellar Structure Survey of Galaxies) samples and find very good agreement. These comparisons include morphology, radial projected density profiles, shapes, sizes and fluxes. We observe the barlens component in our simulations from different viewing angles. This reveals that {\\it barlenses are the vertically thick part of the bar seen face-on, i.e. that a barlens seen edge-on is a boxy/peanut/X bulge}. This finding makes it possible to follow barlens d...

  2. Kinematic imprints from the bar and spiral structures in the galatic disk

    Science.gov (United States)

    Figueras, F.; Antoja, T.; Valenzuela, O.; Romero-Gómez, M.; Pichardo, B.; Moreno, E.

    2011-12-01

    At 140 years of the discovery of the moving groups, these stellar streams are emerging as powerful tools to constrain the models for the spiral arms and the Galactic bar in the Gaia era. From the kinematic-age-metallicity analysis in the solar neighbourhood it is now well established that some of these kinematic structures have a dynamical origin, different from the classical cluster disruption hypothesis. Test particle simulations allow us to definitively establish that these local structures can be created by the dynamical resonances of material spiral arms and not exclusively by the Galactic bar. First studies to evaluate the capabilities of the future Gaia data to detect and characterize moving groups at 2-6 kpc from the solar neighborhood are discussed.

  3. On the wave nature of the spiral structure of Galaxies I. The linear theory (Part I)

    International Nuclear Information System (INIS)

    The spiral density waves are considered in terms of cooperative phenomena in a model galaxy involving differently rotating and non-rotating subsystems. The latter represented population I and II of normal spirals accordingly. Due to inherent for such a system Landau-instability the stationary state with excited spiral waves of finite amplitude may be settled. According to a proposed hypothesis these waves should be identified with spiral structure of galaxies. The work has four parts. The first and second parts deal with linear theory of density waves, the third one treats the nonlinear theory, and are fourth are gives a physical interpretation of the theory and astronomical consequences

  4. Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies.From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r0 to the galactic center) of the spiral arm, and finally the thickness.

  5. The spiral structure of the Galaxy revealed by CS sources and evidence for the 4:1 resonance

    Science.gov (United States)

    Lépine, J. R. D.; Roman-Lopes, A.; Abraham, Zulema; Junqueira, T. C.; Mishurov, Yu. N.

    2011-06-01

    We present a map of the spiral structure of the Galaxy, as traced by molecular carbon monosulphide (CS) emission associated with IRAS sources which are believed to be compact H II regions. The CS line velocities are used to determine the kinematic distances of the sources in order to investigate their distribution in the galactic plane. This allows us to use 870 objects to trace the arms, a number larger than that of previous studies based on classical H II regions. The distance ambiguity of the kinematic distances, when it exists, is solved by different procedures, including the latitude distribution and an analysis of the longitude-velocity diagram. The study of the spiral structure is complemented with other tracers: open clusters, Cepheids, methanol masers and H II regions. The well-defined spiral arms are seen to be confined inside the corotation radius, as is often the case in spiral galaxies. We identify a square-shaped sub-structure in the CS map with that predicted by stellar orbits at the 4:1 resonance (four epicycle oscillations in one turn around the galactic centre). The sub-structure is found at the expected radius, based on the known pattern rotation speed and epicycle frequency curve. An inner arm presents an end with strong inwards curvature and intense star formation that we tentatively associate with the region where this arm surrounds the extremity of the bar, as seen in many barred galaxies. Finally, a new arm with concave curvature is found in the Sagitta to Cepheus region of the sky. The observed arms are interpreted in terms of perturbations similar to grooves in the gravitational potential of the disc, produced by crowding of stellar orbits.

  6. Vertical Scale Parameter Estimates for 48 Non-edge-on Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    Jun Ma

    2003-01-01

    In the first paper of this series, we directly studied the mathematical forms, symmetry of spiral structure, and the projection of galactic discs on the images, and measured the pitch angles of the spiral arms and inclination angles of the galactic discs for 60 spiral galaxies. In this second paper, we estimate the vertical scale parameters of 48 non-edge-on spiral galaxies based on the method proposed by Peng et al. and on the results given in Paper I. As we know, for edge-on disc galaxies we can obtain the vertical scale parameter from the photometry, once a mathematical form is specified for the vertical light distribution. For non-edgeon galaxies, some other methods have to be used. The statistical result was that the vertical scale parameter is comparable for edge-on and non-edge-on galaxies,although it is obtained from two very different methods.

  7. SCALE-LENGTH DETERMINATIONS OF EXPONENTIAL DISKS OF SPIRAL GALAXIES - A COMPARISON

    NARCIS (Netherlands)

    KNAPEN, JH; VANDERKRUIT, PC

    1991-01-01

    Values for the scale lengths h of the exponential discs of spiral galaxies, as found by different authors, have been compared. For a given galaxy, two published values for h may show a discrepancy of almost a factor two. The average value of the discrepancy for more than 120 galaxies is 23%, with a

  8. Dissecting the spiral galaxy M83: mid-infrared emission and comparison with other tracers of star formation

    CERN Document Server

    Vogler, A; Beck, R; Lundgren, A A; Sauvage, M; Vigroux, L; Ehle, M

    2005-01-01

    We present a detailed mid-infrared study of the nearby, face-on spiral galaxy M83 based on ISOCAM data. M83 is a unique case study, since a wide variety of MIR broad-band filters as well as spectra, covering the wavelength range of 4 to 18\\mu m, were observed and are presented here. Emission maxima trace the nuclear and bulge area, star-formation regions at the end of the bar, as well as the inner spiral arms. The fainter outer spiral arms and interarm regions are also evident in the MIR map. Spectral imaging of the central 3'x3' (4 kpc x 4 kpc) field allows us to investigate five regions of different environments. The various MIR components (very small grains, polycyclic aromatic hydrocarbon (PAH) molecules, ionic lines) are analyzed for different regions throughout the galaxy. In the total 4\\mu m to 18\\mu m wavelength range, the PAHs dominate the luminosity, contributing between 60% in the nuclear and bulge regions and 90% in the less active, interarm regions. Throughout the galaxy, the underlying continuum...

  9. The Dragonfly Nearby Galaxies Survey. I. Substantial variation in the diffuse stellar halos around spiral galaxies

    CERN Document Server

    Merritt, Allison; Abraham, Roberto; Zhang, Jielai

    2016-01-01

    Galaxies are thought to grow through accretion; as less massive galaxies are disrupted and merge over time, their debris results in diffuse, clumpy stellar halos enveloping the central galaxy. Here we present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep ($\\mu_{g} > 31$ mag arcsec$^{-2}$) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. Our sample includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of $16-90$ degrees and distances between $7-18$ Mpc. We construct stellar mass surface density profiles from the observed $g$-band surface brightness in combination with the $g-r$ color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk$+$bulge fit) beyond $5$ half-mass radii. We find a mean halo fraction of $0.009 \\pm 0.005$ and a large RMS scatter of $1.01^{+0.9}_{-0.26}$ dex. The...

  10. Applying Schwarzschild's orbit superposition method to barred or non-barred disc galaxies

    CERN Document Server

    Vasiliev, Eugene

    2015-01-01

    We present an implementation of the Schwarzschild orbit superposition method which can be used for constructing self-consistent equilibrium models of barred or non-barred disc galaxies, or of elliptical galaxies with figure rotation. This is a further development of the publicly available code SMILE; its main improvements include a new efficient representation of an arbitrary gravitational potential using two-dimensional spline interpolation of Fourier coefficients in the meridional plane, as well as the ability to deal with rotation of the density profile and with multicomponent mass models. We compare several published methods for constructing composite axisymmetric disc--bulge--halo models and demonstrate that our code produces the models that are closest to equilibrium. We also apply it to create models of triaxial elliptical galaxies with cuspy density profiles and figure rotation, and find that such models can be found and are stable over many dynamical times in a wide range of pattern speeds and angula...

  11. Gas Dynamics and Outflow in the Barred Starburst Galaxy NGC 1808 Revealed with ALMA

    CERN Document Server

    Salak, Dragan; Hatakeyama, Takuya; Miyamoto, Yusuke

    2016-01-01

    NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear region. To study the inflow and outflow processes related to star formation and dynamical evolution of the galaxy, we have carried out \\(^{12}\\)CO (\\(J=1-0\\)) mapping observations of the central \\(r\\sim4\\) kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array (ALMA). Four distinct components of molecular gas are revealed at high spatial resolution of 2\\arcsec (\\(\\sim100\\) pc): (1) a compact (\\(r<200\\) pc) circumnuclear disk (CND), (2) \\(r\\sim500\\) pc ring, (3) gas-rich galactic bar, and (4) spiral arms. Basic geometric and kinematic parameters are derived for the central 1-kpc region using tilted-ring modeling. The derived rotation curve reveals multiple mass components that include (1) a stellar bulge, (2) nuclear bar and molecular CND, and (3) unresolved massive (\\(\\sim10^7~M_\\sun\\)) core. Two systemic velocities, 998 km s\\(^{-1}\\) for the CND and 964 km s\\(^{-1}\\) for the 500-pc ring, are revealed, indicating ...

  12. Kinematic Evolution of Field and Cluster Spiral Galaxies

    CERN Document Server

    Ziegler, Bodo

    2014-01-01

    We investigate the evolution of the Tully-Fisher relation out to z=1 with 137 emission-line galaxies in the field that display a regular rotation curve. They follow a linear trend with lookback time being on average brighter by 1.1Bmag and 60% smaller at z=1. For a subsample of 48 objects with very regular gas kinematics and stellar structure we derive a TF scatter of 1.15mag, which is two times larger than local samples exhibit. This is probably due to modest variations in their star formation history and chemical enrichment. In another study of 96 members of Abell 901/902 at z=0.17 and 86 field galaxies with similar redshifts we find a difference in the TFR of 0.42mag in the B-band but no significant difference in stellar mass. Comparing specifically red spirals with blue ones in the cluster, the former are fainter on average by 0.35Bmag and have 15% lower stellar masses. This is probably due to star formation quenching caused by ram-pressure in the cluster environment. Evidence for this scenario comes from...

  13. Spiral galaxies rotation curves in the Horava - Lifshitz gravity theory

    CERN Document Server

    Cardone, Vincenzo F; Radicella, Ninfa; Ruggiero, Matteo L

    2012-01-01

    We focus on a modified version of Horava - Lifschitz theory and, in particular, we consider the impact of its weak - field static spherically symmetric limit on the galaxy dynamics. In a previous paper, we used the modified gravitational potential obtained in this theory to evaluate the Milky Way rotation curve using a spheroidal truncated power - law bulge and a double exponential disc as the only sources of the gravitational field and showed that the modified rotation curved is not in agreement with the data. Making a step forward, we here include also the contribution from a dark matter halo in order to see whether this helps fitting the rotation curve data. As a test case, we consider a sample of spiral galaxies with smooth baryon matter distribution and well measured circular velocity profiles. It turns out that, although a marginal agreement with the data can be found, this can only be obtained if the dark matter halo has an unrealistically small virial mass and incredibly large concentration. Such resu...

  14. Cold dust in giant barred galaxy NGC1365

    CERN Document Server

    Tabatabaei, F S; Combes, F; Henkel, C; Menten, K M; Beck, R; Kovács, A; Guesten, R

    2013-01-01

    Observations of galaxies at sub-millimeter wavelengths, where the emission is mainly due to cold dust, are required to constrain the dust physical properties and provide important insight on the gas content of galaxies. We mapped NGC1365 at 870um with LABOCA, the Large APEX Bolometer Camera, allowing us to probe the central mass concentration as well as the rate at which the gas flows to the center. We obtained the dust physical properties both globally and locally for different locations in the galaxy. A 20 K modified black body represents about 98% of the total dust content of the galaxy, the rest can be represented by a warmer dust component of 40 K. The bar exhibits an east-west asymmetry in the dust distribution: The eastern bar is heavier than the western bar by more than a factor of 4. Integrating the dust SED, we derive a total infrared (IR) luminosity of 9.8 x 10^{10} L_{\\odot} leading to a dust-enshrouded star formation rate of ~16.7 M_{\\odot} per year in NGC1365. We derive the gas mass from the mea...

  15. Spiral Galaxy Mass Models and the Distance Scale

    Science.gov (United States)

    Palunas, P.; Williams, T. B.

    1993-12-01

    We present mass models for a sample of Freeman Type I spiral galaxies taken from the southern sky Fabry-Perot Tully-Fisher survey(Schommer \\etal 1993, Bothun \\etal 1992). We fit two component, bulge and disk, photometric models directly to I- and R-band images. The bulge model is a series expansion of Gaussians (a Gabor expansion): each Gaussian in the series has a common center, ellipticity and position angle. The position angle is fixed to be the same as that of the disk. We have found that a deVaucouleurs law does not give a good fit to the bulges of many disk galaxies. The disk model is an exponential with the same center as the bulge. Small-scale radial structure is included in the disk mass model by azimuthally averaging the residuals of the analytic fit in annuli with the same ellipticity and position angle of the disk. Fitting to the full 2-d images helps constrain the disk-bulge deconvolution by using the information in the different ellipticities well as the different radial profiles of the disk and bulge. The photometric model is fitted to the rotation curve assuming a maximum disk and constant mass-to-light ratios for disk and bulge components. The small scale structure in the photometric models is found to reproduce the structure in the rotation curve in many galaxies. We find approximately 15 percent rms scatter in the I-band mass-to-light ratios, as well as correlations to the detailed properties of the kinematics indicating that mass-to-light ratios may be useful in reducing the scatter in the Tully-Fisher relation. Bothun, G.D., Schommer, R.A., Williams, T.B., Mould J.R., Huchra, J.P. 1992, Ap.J., 388, 253. Schommer, R.A., Bothun, G.D., Williams, T.B., Mould J.R. 1993, A.J., 105, 97.

  16. The origin of nitrogen and the chemical evolution of spiral galaxies

    OpenAIRE

    Angeles I. Díaz; Tosi, M.

    1986-01-01

    This is an electronic version of an article published in Astronomy and Astrophysics. Diaz, A.I. and M. Tosi. The origin of nitrogen and the chemical evolution of spiral galaxies. Astronomy and Astrophysics 158 (1986): 60-66

  17. The opacity of spiral galaxy disks. III. Automating the synthetic field method

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. developed a method for this calibration, the Synthetic Fi

  18. THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Marinova, Irina; Jogee, Shardha; Weinzirl, Tim [Department of Astronomy, University of Texas at Austin, Austin, TX (United States); Erwin, Peter [Max-Planck-Insitut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Trentham, Neil [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Ferguson, Henry C.; Goudfrooij, Paul [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hammer, Derek [Department of Physics and Astronomy, Johns Hopkins, Baltimore, MD 21218 (United States); Den Brok, Mark; Peletier, Reynier F.; Kleijn, Gijs V. [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Graham, Alister W. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn (Australia); Carter, David; Mouhcine, Mustapha [Astrophysics Research Institute, Liverpool John Moores University, Birkenhead (United Kingdom); Balcells, Marc [Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife (Spain); Guzman, Rafael; Hoyos, Carlos [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Mobasher, Bahram [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Peng, Eric W., E-mail: marinova@astro.as.utexas.edu, E-mail: sj@astro.as.utexas.edu [Department of Astronomy, Peking University, Beijing 100871 (China)

    2012-02-20

    low-density environments for two reasons. First, S0s in rich clusters are less prone to bar instabilities as they are dynamically heated by harassment and are gas poor as a result of ram pressure stripping and accelerated star formation. Second, high-speed encounters in rich clusters may be less effective than slow, strong encounters in inducing bars. (3) We also take advantage of the high resolution of the ACS ({approx}50 pc) to analyze a sample of 333 faint (M{sub V} > -18) dwarf galaxies in the Coma core. Using visual inspection of unsharp-masked images, we find only 13 galaxies with bar and/or spiral structure. An additional eight galaxies show evidence for an inclined disk. The paucity of disk structures in Coma dwarfs suggests that either disks are not common in these galaxies or that any disks present are too hot to develop instabilities.

  19. THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

    International Nuclear Information System (INIS)

    less prone to bar instabilities as they are dynamically heated by harassment and are gas poor as a result of ram pressure stripping and accelerated star formation. Second, high-speed encounters in rich clusters may be less effective than slow, strong encounters in inducing bars. (3) We also take advantage of the high resolution of the ACS (∼50 pc) to analyze a sample of 333 faint (MV > –18) dwarf galaxies in the Coma core. Using visual inspection of unsharp-masked images, we find only 13 galaxies with bar and/or spiral structure. An additional eight galaxies show evidence for an inclined disk. The paucity of disk structures in Coma dwarfs suggests that either disks are not common in these galaxies or that any disks present are too hot to develop instabilities.

  20. The flaring Hi disk of the nearby spiral galaxy NGC 2683

    Science.gov (United States)

    Vollmer, B.; Nehlig, F.; Ibata, R.

    2016-02-01

    New deep VLA D array Hi observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model Hi data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80°; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination between 10 kpc ≤ R ≤ 20 kpc (decreasing by 10°); (iv) an exponential flare that rises from 0.5 kpc at R = 9 kpc to 4 kpc at R = 15 kpc, stays constant until R = 22 kpc, and decreases its height for R> 22 kpc; and (v) a low surface-density gas ring with a vertical offset of 1.3 kpc. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the optical and thin gas disk. Under the assumption of vertical hydrostatic equilibrium we derive the vertical velocity dispersion of the gas. The high turbulent velocity dispersion in the flare can be explained by energy injection by (i) supernovae; (ii) magneto-rotational instabilities; (iii) interstellar medium stirring by dark matter substructure; or (iv) external gas accretion. The existence of the complex large-scale warping and asymmetries favors external gas accretion as one of the major energy sources that drives turbulence in the outer gas disk. We propose a scenario where this external accretion leads to turbulent adiabatic compression that enhances the turbulent velocity dispersion and might quench star formation in the outer gas disk of NGC

  1. A Comparative Study of Knots of Star Formation in Interacting vs. Spiral Galaxies

    CERN Document Server

    Smith, Beverly J; Struck, Curtis; Olmsted, Susan; Jones, Keith

    2016-01-01

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published H-alpha images, we have compared the star formation rates of ~700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high star formation rates than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The star formation rates of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest star formation rates, the apparent dust a...

  2. Aperture corrections for disk galaxy properties derived from the CALIFA survey. Balmer emission lines in spiral galaxies

    CERN Document Server

    Iglesias-Páramo, J; Galbany, L; Sánchez, S F; Rosales-Ortega, F F; Mast, D; García-Benito, R; Husemann, B; Aguerri, J A L; Alves, J; Bekeraité, S; Bland-Hawthorn, J; Catalán-Torrecilla, C; de Amorim, A L; de Lorenzo-Cáceres, A; Ellis, S; Falcón-Barroso, J; Flores, H; Florido, E; Gallazzi, A; Gomes, J M; Delgado, R M González; Haines, T; Hernández-Fernández, J D; Kehrig, C; López-Sánchez, A R; Lyubenova, M; Marino, R A; Mollá, M; Monreal-Ibero, A; Mourão, A; Papaderos, P; Sánchez-Blázquez, P; Spekkens, K; Stanishev, V; van de Ven, G; Walcher, C J; Wisotzki, L; Zibetti, S; Ziegler, B

    2013-01-01

    This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We have used 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we have derived growth curves of the most conspicuous Balmer emission lines (Halpha, Hbeta) for circular apertures of different radii centered at the galaxy's nucleus after removing the underlying stellar continuum. We find that the Halpha flux (f(Halpha)) growth curve follows a well defined sequence with aperture radius showing low dispersion around the median value. From this analysis, we derive aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Halpha)/f(Hbeta) ratio growth curve shows...

  3. The cored distribution of dark matter in spiral galaxies

    CERN Document Server

    Gentile, G; Klein, U; Vergani, D; Kalberla, P

    2004-01-01

    We present the HI data for 5 spiral galaxies that, along with their Halpha rotation curves, are used to derive the distribution of dark matter within these objects. A new method for extracting rotation curves from HI data cubes is presented; this takes into account the existence of a warp and minimises projection effects. The rotation curves obtained are tested by taking them as input to construct model data cubes that are compared to the observed ones: the agreement is excellent. On the contrary, the model data cubes built using rotation curves obtained with standard methods, such as the first-moment analysis, fail the test. The HI rotation curves agree well with the Halpha data, where they coexist. Moreover, the combined Halpha + HI rotation curves are smooth, symmetric and extended to large radii. The rotation curves are decomposed into stellar, gaseous and dark matter contributions and the inferred density distribution is compared to various mass distributions: dark haloes with a central density core, $\\L...

  4. Scaling Relations in Dissipationless Spiral-like Galaxy Mergers

    CERN Document Server

    Aceves, H; Cruz, F

    2009-01-01

    We determine both representations of the Fundamental Plane [Re Sig^a Ie^b and Re (Sig^2/Ie)^lambda] and the luminosity-effective phase space density [L fe^(-gamma)] scaling relation for N-body remnants of binary mergers of spiral-like galaxies. The main set of merger simulations involves a mass-ratio of the progenitors in the range of about 1:1 to 1:5, harboring or not a bulge-like component, and are constructed using a cosmological motivated model. Equal-mass mergers are also considered. Remnants lead to average values for the scaling indices of ~1.6, ~0.6, ~0.7, and ~0.65. These values are consistent with those of K--band observations (Mobasher et al. 1999) of ellipticals: ~1.5, ~0.8, ~0.7, and ~0.60. The b index is, however, not well reproduced. This study does not allow us to establish a conclusive preference for models with or without a bulge as progenitors. Our results indicate that the L--fe and FP scalings might be determined to a large extent by dissipationless processes, a result that appears to be ...

  5. An Atlas for Structural Studies of Spiral Galaxies

    CERN Document Server

    Courteau, S

    1999-01-01

    This is an announcement of a new database of structural properties for 304 late-type (Sb-Sc) spiral galaxies drawn from the UGC catalogue. These data were compiled from the kinematic and photometric studies of Courteau (1996, 1997), and are made available to the community via the Canadian Astronomy Data Centre. The data base contains redshift information and Tully-Fisher distances, various measures of optical (Halpha) line width and rotational velocity, isophotal diameters and magnitudes, disk scale lengths, B-r colour, rotation curve model parameters, and more. The main table includes 66 entries (columns); it can be down-loaded as one single file, or searched for any range of parameters using our search engine. The data files for each rotation curve and luminosity profile (including multiple observations) are also available and can be retrieved as two separate tar files. These data were originally obtained for cosmic flow studies (e.g. Courteau etal 1993, Courteau 1993) and have been included in the Mark III...

  6. Spiral density wave triggering of star formation in SA and SAB galaxies

    CERN Document Server

    Martínez-García, Eric E; Bruzual-A, Gustavo

    2008-01-01

    Azimuthal color (age) gradients across spiral arms are one of the main predictions of density wave theory; gradients are the result of star formation triggering by the spiral waves. In a sample of 13 spiral galaxies of types A and AB, we find that 10 of them present regions that match the theoretical predictions. By comparing the observed gradients with stellar population synthesis models, the pattern speed and the location of major resonances have been determined. The resonance positions inferred from this analysis indicate that 9 of the objects have spiral arms that extend to the outer Lindblad resonance (OLR); for one of the galaxies, the spiral arms reach the corotation radius. The effects of dust, and of stellar densities, velocities, and metallicities on the color gradients are also discussed.

  7. H-alpha observations of spiral galaxies in Cancer, A1367, and Coma

    International Nuclear Information System (INIS)

    We have used large aperture Hα photometry of 65 spiral galaxies in the Cancer, Coma, and Abell 1367 clusters to compare the ionized-gas contents and star-formation rates in cluster and field spirals. Overall, we do not observe any significant deficiency of Hα emission in the cluster members. Emission strength correlates strongly with integrated galaxy colors, but only weakly with H I content. All three clusters contain several galaxies with unusually strong Hα emission, including several H I-poor objects in Coma and A1367. Thus, spirals which appear ''anemic'' in their morphology or exhibit weak Hα emission are not necessarily H I poor; conversely, H I poor spirals can show strong Hα emission, indicating relatively high current star-formation rates. Gas depletion time scales for some objects in the core of Coma are significantly shorter than the field, indicating rapid stellar and gaseous evolution

  8. EXTENDED ROTATION CURVES OF SPIRAL GALAXIES - DARK HALOES AND MODIFIED DYNAMICS

    NARCIS (Netherlands)

    BEGEMAN, KG; BROEILS, AH; SANDERS, RH

    1991-01-01

    Strict criteria are applied to the sample of spiral galaxies with measured rotation curves in order to select those objects for which the observed rotation curve is an accurate tracer of the radial force law. The resulting sub-sample of 10 galaxies is then considered in view of two suggested explana

  9. The published extended rotation curves of spiral galaxies : Confrontation with modified dynamics

    NARCIS (Netherlands)

    Sanders, RH

    1996-01-01

    A sample of 22 spiral galaxy rotation curves, measured in the 21 cm line of neutral hydrogen, is considered in the context of Milgrom's modified dynamics (MOND). Combined with the previous, highly selected sample of Begeman et al., this constitutes the current total sample of galaxies with published

  10. The opacity of spiral galaxy disks : IX. Dust and gas surface densities

    NARCIS (Netherlands)

    Holwerda, B. W.; Allen, R. J.; de Blok, W. J. G.; Bouchard, A.; Gonzalez-Lopezlira, R. A.; van der Kruit, P. C.; Leroy, A.

    2013-01-01

    Our aim is to explore the relation between gas, atomic and molecular, and dust in spiral galaxies. Gas surface densities are from atomic hydrogen and CO line emission maps. To estimate the dust content, we use the disk opacity as inferred from the number of distant galaxies identified in twelve HST/

  11. Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms

    CERN Document Server

    Aramyan, L S; Petrosian, A R; de Lapparent, V; Bertin, E; Mamon, G A; Kunth, D; Nazaryan, T A; Adibekyan, V; Turatto, M

    2016-01-01

    Using a sample of 215 supernovae (SNe), we analyze their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of...

  12. Anti-truncated stellar light profiles in the outer regions of STAGES spiral galaxies: bulge or disc related?

    CERN Document Server

    Maltby, David T; Gray, Meghan E; Aragón-Salamanca, Alfonso; Wolf, Christian

    2011-01-01

    We present a comparison of azimuthally averaged radial surface brightness mu(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r^(1/4) bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated mu(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius r_brk. The excess light at large radii (r > r_brk) can either be caused by an outer exponential disc (Type III-d) or an extended spheroidal component (Type III-s). Using our comparisons, we determine the contribution of bulge light at r > r_brk for a large sample of 78 (barred/unbarred, Sa-Sd) spiral galaxies with outer disc antitruncations (mu_brk > 24 mag arcsec^-2). In the majority of cases (~85 per cent), evidence indicates that excess light at r > r_brk is related to an outer shallow disc (Type III-d). Here, th...

  13. DEPENDENCE OF NEBULAR HEAVY-ELEMENT ABUNDANCE ON H I CONTENT FOR SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals

  14. Dependence of Nebular Heavy-element Abundance on H I Content for Spiral Galaxies

    Science.gov (United States)

    Robertson, Paul; Shields, Gregory A.; Davé, Romeel; Blanc, Guillermo A.; Wright, Audrey

    2013-08-01

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  15. Dependence of Nebular Heavy-Element Abundance on H I Content for Spiral Galaxies

    CERN Document Server

    Robertson, Paul; Davé, Romeel; Blanc, Guillermo A; Wright, Audrey

    2013-01-01

    We analyze the galactic H I content and nebular log(O/H) for 60 spiral galaxies in the Moustakas et al. (2006) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log(O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  16. DEPENDENCE OF NEBULAR HEAVY-ELEMENT ABUNDANCE ON H I CONTENT FOR SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Paul; Shields, Gregory A.; Wright, Audrey [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Dave, Romeel [Astronomy Department, University of Arizona, Tucson, AZ 85721 (United States); Blanc, Guillermo A., E-mail: paul@astro.as.utexas.edu [Carnegie Observatories, Pasadena, CA 91101-1292 (United States)

    2013-08-10

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  17. Two-Dimensional Magnetohydrodynamic Simulations of Barred Galaxies

    CERN Document Server

    Kim, Woong-Tae

    2012-01-01

    Barred galaxies are known to possess magnetic fields that may affect the properties of bar substructures such as dust lanes and nuclear rings. We use two-dimensional high-resolution magnetohydrodynamic (MHD) simulations to investigate the effects of magnetic fields on the formation and evolution of such substructures as well as on the mass inflow rates to the galaxy center. The gaseous medium is assumed to be infinitesimally-thin, isothermal, non-self-gravitating, and threaded by initially uniform, azimuthal magnetic fields. We find that there exists an outermost x1-orbit relative to which gaseous responses to an imposed stellar bar potential are completely different between inside and outside. Inside this orbit, gas is shocked into dust lanes and infalls to form a nuclear ring. Magnetic fields are compressed in dust lanes, reducing their peak density. Magnetic stress removes further angular momentum of the gas at the shocks, temporarily causing the dust lanes to bend into an 'L' shape and eventually leading ...

  18. Secular- and merger-built bulges in barred galaxies

    CERN Document Server

    Mendez-Abreu, J; Corsini, E M; Aguerri, J A L

    2014-01-01

    (Abridged) We study the incidence, as well as the nature, of composite bulges in a sample of 10 face-on barred galaxies to constrain the formation and evolutionary processes of the central regions of disk galaxies. We analyze the morphological, photometric, and kinematic properties of each bulge. Then, by using a case-by-case analysis we identify composite bulges and classify every component into a classical or pseudobulge. In addition, bar-related boxy/peanut (B/P) structures were also identified and characterised. We find only three galaxies hosting a single-component bulge (two pseudobulges and one classical bulge). We find evidence of composite bulges coming in two main types based on their formation: secular-built and merger- and secular-built. We call secular-built to composite bulges made of entirely by structures associated with secular processes such as pseudo bulges, central disks, or B/P bulges. We find four composite bulges of this kind in our sample. On the other hand, merger- and secular-built b...

  19. Chaos caused by resonance overlap in the solar neighborhood -- Spiral structure at the Bar's 2:1 outer Lindblad resonance

    OpenAIRE

    Quillen, A. C.

    2002-01-01

    We consider the nature of orbits near the solar neighborhood which are perturbed by local spiral arms and the Milky Way bar. We present a simplified Hamiltonian model which includes resonant terms from both types of perturbations and is similar to the forced pendulum. Via numerical integration of this model we construct Poincare maps to illustrate the nature and stability of the phase space. We find that resonance overlap is most likely to cause widespread chaos when the pattern of the spiral...

  20. HI-deficient spiral galaxies in the Coma cluster and Abell 1367

    International Nuclear Information System (INIS)

    A sample of 11 spiral galaxies in each of the clusters Abell 1367 and Coma (Abell 1656) was observed in the 21-cm H I line with the Arecibo 305-m radio telescope. Nine galaxies are detected in Al367 and three in Coma. Comparison of the quantity log M/sub H/L/sub pg/ for each galaxy with the mean value for its Hubble type from the standard samples of nearby spirals compiled by Balkowski and by Roberts indicates that the A1367 and Coma spirals have lower values of log M/sub H/L/sub pg/ than field spirals by a factor of at least 4, with the Coma values probably more extreme. It is argued that little of this effect (perhaps a factor approx. 1.5) can be attributed to the bias toward high luminosities in the sample, and thus that these spirals are deficient in H I by factors of at least 3 to 5 in comparison with the standard samples. For the present limited sample, several mechanisms seem adequate to account qualitatively for stripping of H I from the Coma cluster spirals, but the case of the A1367 spirals is puzzling. 2 figures

  1. The different star-formation histories of blue and red spiral and elliptical galaxies

    CERN Document Server

    Tojeiro, Rita; Richards, Joshua; Percival, Will J; Bamford, Steven P; Maraston, Claudia; Nichol, Robert C; Skibba, Ramin; Thomas, Daniel

    2013-01-01

    [Abridged] We study the spectral properties of intermediate mass galaxies as a function of colour and morphology. We use Galaxy Zoo to define three morphological classes of galaxies, namely early-types (ellipticals), late-type (disk-dominated) face-on spirals and early-type (bulge-dominated) face-on spirals. We classify these galaxies as blue or red according to their SDSS g-r colour and use the spectral fitting code VESPA to calculate time-resolved star-formation histories, metallicity and total starlight dust extinction from their SDSS fibre spectra. We find that red late-type spirals show less star-formation in the last 500 Myr than blue late-type spirals by up to a factor of three, but share similar star-formation histories at earlier times. This decline in recent star-formation explains their redder colour: their chemical and dust content are the same. We postulate that red late-type spirals are recent descendants of blue late-type spirals, with their star-formation curtailed in the last 500 Myrs. The re...

  2. Connecting Global to Local Parameters in Barred Galaxy Models

    Indian Academy of Sciences (India)

    N. D. Caranicolas

    2002-09-01

    We present connections between global and local parameters in a realistic dynamical model, describing motion in a barred galaxy. Expanding the global model in the vicinity of a stable Lagrange point, we find the potential of a two-dimensional perturbed harmonic oscillator, which describes local motion near the centre of the global model. The frequencies of oscillations and the coefficients of the perturbing terms are not arbitrary but are connected to the mass, the angular rotation velocity, the scale length and the strength of the galactic bar. The local energy is also connected to the global energy. A comparison of the properties of orbits in the global and local potential is also made.

  3. Time-dependent Corotation Resonance in Barred Galaxies

    CERN Document Server

    Wu, Yu-Ting; Taam, Ronald E

    2016-01-01

    The effective potential neighboring the corotation resonance region in barred galaxies is shown to be strongly time-dependent in any rotating frame because of the competition of nearby perturbations of similar strengths with differing rotation speeds. Contrary to the generally adopted assumption, that in the bar rotating frame the corotation region should possess four stationary equilibrium points (Lagrange points), with high quality N-body simulations we localize the instantaneous equilibrium points and find that they circulate or oscillate broadly in azimuth with respect to the pattern speeds of the inner or outer perturbations. This implies that at the particle level the Jacobi integral is not well conserved around the corotation radius. That is, angular momentum exchanges decouple from energy exchanges, enhancing the chaotic diffusion of stars through the corotation region.

  4. Evidence of Bar-induced Secular Evolution in the Inner Regions of Stellar Discs in Galaxies: What Shapes Disc Galaxies?

    CERN Document Server

    Kim, Taehyun; Athanassoula, E; Bosma, Albert; Sheth, Kartik; Lee, Myung Gyoon

    2016-01-01

    We present evidence of bar-induced secular evolution in galactic discs using 3.6 ${\\mu m}$ images of nearby galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We find that among massive galaxies ($M_{star}/M_{sun}> 10^{10}$), longer bars tend to reside in inner discs having a flatter radial profile. Such galaxies show a light deficit in the disc surrounding the bar, within the bar radius and often show a $\\Theta$-shaped morphology. We quantify this deficit and find that among all galaxies explored in this study (with $10^{9}galaxies with a stronger bar (i.e. longer and/or with a higher Bar/T) show a more pronounced deficit. We also examine simulation snapshots to confirm and extend results by Athanassoula and Misiriotis, showing that as bars evolve they become longer, while the light deficit in the disc becomes more pronounced. Theoretical studies have predicted that, as a barred galaxy evolves, the bar captures disc stars in its immediate neighbourhoo...

  5. Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms

    Science.gov (United States)

    Aramyan, L. S.; Hakobyan, A. A.; Petrosian, A. R.; de Lapparent, V.; Bertin, E.; Mamon, G. A.; Kunth, D.; Nazaryan, T. A.; Adibekyan, V.; Turatto, M.

    2016-07-01

    Using a sample of 215 supernovae (SNe), we analyse their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of CC SNe (known to have short-lived progenitors). The closer locations of SNe Ibc versus SNe II relative to the leading edges of the arms supports the belief that SNe Ibc have more massive progenitors. SNe Ia having less massive and older progenitors, have more time to drift away from the leading edge of the spiral arms.

  6. The impact of dark matter cusps and cores on the satellite galaxy population around spiral galaxies

    CERN Document Server

    Penarrubia, Jorge; Walker, Matthew G; Gilmore, Gerard; McConnachie, Alan; Mayer, Lucio

    2010-01-01

    (Abridged) We use N-body simulations to study the effects that a divergent (i.e. "cuspy") dark matter (DM) profile introduces on the tidal evolution of dwarf spheroidal galaxies (dSphs). Our models assume cosmologically-motivated initial conditions where dSphs are DM-dominated systems on eccentric orbits about a host galaxy composed of a dark halo and a baryonic disc. We find that the resilience of dSphs to tidal stripping is extremely sensitive to the halo cuspiness; whereas dwarfs with a cored profile can be easily destroyed by the host disc, those with cusps always retain a bound remnant. For a given halo profile the evolution of the structural parameters as driven by tides is controlled solely by the total amount of mass lost. This information is used to construct a semi-analytic code that simulates the hierarchical build-up of spiral galaxies assuming different halo profiles and disc masses. We find that tidal encounters with discs tend to decrease the average mass of satellites at all galactocentric rad...

  7. The JCMT Nearby Galaxies Legacy Survey I. Star Forming Molecular Gas in Virgo Cluster Spiral Galaxies

    CERN Document Server

    Wilson, C D; Israel, F P; Serjeant, S; Bendo, G; Brinks, E; Clements, D; Courteau, S; Irwin, J; Knapen, J H; Leech, J; Matthews, H E; Muehle, S; Mortier, A M J; Petitpas, G; Sinukoff, E; Spekkens, K; Tan, B K; Tilanus, R P J; Usero, A; Van der Werf, P P; Wiegert, T; Zhu, M

    2008-01-01

    We present large-area maps of the CO J=3-2 emission obtained at the James Clerk Maxwell Telescope for four spiral galaxies in the Virgo Cluster. We combine these data with published CO J=1-0, 24 micron, and Halpha images to measure the CO line ratios, molecular gas masses, and instantaneous gas depletion times. For three galaxies in our sample (NGC 4254, NGC4321, and NGC 4569), we obtain molecular gas masses of 7E8-3E9 Msun and disk-averaged instantaneous gas depletion times of 1.1-1.7 Gyr. We argue that the CO J=3-2 line is a better tracer of the dense star forming molecular gas than the CO J=1-0 line, as it shows a better correlation with the star formation rate surface density both within and between galaxies. NGC 4254 appears to have a larger star formation efficiency(smaller gas depletion time), perhaps because it is on its first passage through the Virgo Cluster. NGC 4569 shows a large-scale gradient in the gas properties traced by the CO J=3-2/J=1-0 line ratio, which suggests that its interaction with ...

  8. Variations in Metallicity and Gas Content in Spiral Galaxies: Accidents of Infall

    Science.gov (United States)

    Shields, Gregory A.; Robertson, P.; Dave, R.; Blanc, G. A.; Wright, A.

    2013-01-01

    Oxygen abundances are elevated in hydrogen deficient spirals in the Virgo and Pegasus clusters (Robertson et al. 2012, ApJ 748:48, and references therein). We confirm the relationship between O/H and H I deficiency "DEF" for an additional set of cluster spirals. In addition, we find that field spirals show a similar increase in O/H with DEF. Thus, the relationship is not uniquely the result of environmental processes in clusters. Cosmological simulations of galaxy formation predict a qualitatively similar trend of O/H with DEF for field spirals. This reflects excursions of gas content and metallicity above and below the mean mass-metallicity relationship as galaxies evolve. These excursions result from the stochastic effects of mergers and merger-free periods during the evolution.

  9. Synthetic HI observations of spiral structure in the outer disk in galaxies

    Science.gov (United States)

    Khoperskov, Sergey A.; Bertin, Giuseppe

    2015-12-01

    > By means of 3D hydrodynamical simulations, in a separate paper we have discussed the properties of non-axisymmetric density wave trains in the outermost regions of galaxy disks, based on the picture that self-excited global spiral modes in the bright optical stellar disk are accompanied by low-amplitude short trailing wave signals outside corotation; in the gas, such wave trains can penetrate through the outer Lindblad resonance and propagate outwards, forming prominent spiral patterns. In this paper we present the synthetic 21 cm velocity maps expected from simulated models of the outer gaseous disk, focusing on the case when the disk is dominated by a two-armed spiral pattern, but considering also other more complex situations. We discuss some aspects of the spiral pattern in the gaseous periphery of galaxy disks noted in our simulations that might be interesting to compare with specific observed cases.

  10. Synthetic HI observations of spiral structure in the outer disk in galaxies

    CERN Document Server

    Khoperskov, S A

    2015-01-01

    By means of 3D hydrodynamical simulations, in a separate paper we have discussed the properties of non-axisymmetric density wave trains in the outermost regions of galaxy disks, based on the picture that self-excited global spiral modes in the bright optical stellar disk are accompanied by low-amplitude short trailing wave signals outside corotation; in the gas, such wave trains can penetrate through the outer Lindblad resonance and propagate outwards, forming prominent spiral patterns. In this paper we present the synthetic 21~cm velocity maps expected from simulated models of the outer gaseous disk, focusing on the case when the disk is dominated by a two-armed spiral pattern, but considering also other more complex situations. We discuss some aspects of the spiral pattern in the gaseous periphery of galaxy disks noted in our simulations that might be interesting to compare with specific observed cases.

  11. AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; Jones, E.; Dunlap, H. [Physics Department, University of Richmond 28 Westhampton Way, Richmond, VA 23173 (United States); Kogut, A., E-mail: jsingal@richmond.edu [Code 665, NASA Goddard Space Flight Center Greenbelt, MD 20771 (United States)

    2015-01-20

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

  12. Towards understanding the dynamics of the bar/bulge region in our Galaxy

    Directory of Open Access Journals (Sweden)

    Athanassoula E.

    2012-02-01

    Full Text Available I review some of the work on bars which is closely linked to the bar/bulge system in our Galaxy. Several independent studies, using totally independent methods, come to the same results about the 3D structure of a bar, i.e., that a bar is composed of a vertically thick inner part and a vertically thin outer part. I give examples of this from simulations and substantiate the discussion with input from orbital structure analysis and from observations. The thick part has a considerably shorter radial extent than the thin part. I then see how this applies to our Galaxy, where two bars have been reported, the COBE/DIRBE bar and the Long bar. Comparing their extents and making the reasonable and necessary assumption that our Galaxy has properties similar to those of other galaxies of similar type, leads to the conclusion that these two bars can not form a standard double bar system. I then discuss arguments in favour of the two bars being simply different parts of the same bar, the COBE/DIRBE bar being the thick inner part and the Long bar being the thin outer part of this bar. I also very briefly discuss some related new results. I first consider bar formation and evolution in disc galaxies with a gaseous component – including star formation, feedback and evolution – and a triaxial halo. Then I consider bar formation in a fully cosmological context using hydrodynamical LCDM simulations, where the host galaxies grow, accrete matter and significantly evolve during the formation and evolution of the bar.

  13. Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

    CERN Document Server

    Hart, Ross E; Willett, Kyle W; Masters, Karen L; Cardamone, Carolin; Lintott, Chris J; Mackay, Robert J; Nichol, Robert C; Rosslowe, Christopher K; Simmons, Brooke D; Smethurst, Rebecca J

    2016-01-01

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star-formation in the disks of low-redshift galaxies, so are important in the understanding of star-formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ~18,000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorised by spiral arm number. In order to explore how different spiral galaxies form, the demographic...

  14. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    Science.gov (United States)

    de Souza, R. S.; Dantas, M. L. L.; Krone-Martins, A.; Cameron, E.; Coelho, P.; Hattab, M. W.; de Val-Borro, M.; Hilbe, J. M.; Elliott, J.; Hagen, A.; COIN Collaboration

    2016-09-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, M200, and the normalized cluster centric distance, r/r200. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within an HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g. whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a binary variable. Furthermore, we demonstrate how an HBM can incorporate information of each particular galaxy morphological type in an unified framework. In elliptical galaxies our analysis indicates a strong correlation of Seyfert-AGN activity with r/r200, and a weaker correlation with the mass of the host cluster. In spiral galaxies these trends do not appear, suggesting that the link between Seyfert activity and the properties of spiral galaxies are independent of the environment.

  15. The transformation of Spirals into S0 galaxies in the cluster environment

    Directory of Open Access Journals (Sweden)

    Mauro eD'onofrio

    2015-08-01

    Full Text Available We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04galaxies in clusters is almost a factor of ∼ 3 − 4 larger today than at redshift z ∼ 1; 2 the fraction of S0’s to Spirals increases on average by a factor ∼ 2 every Gyr; 3 the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web is: ∼ 5 Sp→S0’s per Gyr and ∼ 2 Sp→E’s per Gyr; 4 there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5 there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1 the ratio between the number of S0’s and Spirals (NS0/NSp in the WINGS clusters is correlated with their X-ray luminosity LX ; 2 that the brightest and massive S0’s are always close to the cluster center; 3 that the mean Se ́rsic index of S0’s is always larger than that of Spirals (and lower than E’s for galaxy stellar masses above 10^9.5M⊙; 4 that the number of E’s in clusters cannot be constant; 5 that the largest difference between the mean mass of S0’s and E’s with respect to Spirals is observed in clusters with low velocity dispersion.Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Se ́rsic index.

  16. Low-mass spiral galaxies with little molecular gas and prodigious star formation

    Science.gov (United States)

    Kenney, Jeffrey D.; Young, Judith S.

    1988-01-01

    A comparison of CO and H I properties is used here to demonstrate that many CO-poor low-mass Virgo spiral galaxies are rich in atomic gas, which implies that the lack of CO emission from them is due, at least partly, to a lack of molecular gas. Despite the paucity of molecular gas, these H I-rich, CO-poor, low-mass spiral galaxies are undergoing extensive massive star formation. A column density of 10 to the 21st nuclei/sq cm is a necessary but insufficient condition for the creation of an H2-dominated interstellar medium.

  17. Structure and kinematics of candidate double-barred galaxies

    CERN Document Server

    Moiseev, A V; Chavushyan, V H

    2003-01-01

    Results of optical and NIR spectral and photometric observations of a sample of candidate double-barred galaxies are presented. Velocity fields and velocity dispersion maps of stars and ionized gas, continuum and emission-line images were constructed from integral-field spectroscopy observations carried out at the 6m telescope (BTA) of SAO RAS, with the MPFS spectrograph and the scanning Fabry-Perot Interferometer. NGC2681 was also observed with long-slit spectrograph of the BTA. Optical and NIR images were obtained at the BTA and at the 2.1m telescope (OAN, M\\'exico). High-resolution images were retrieved from the HST data archive. Morphological and kinematic features of all 13 sample objects are described in detail. Attention is focused on the interpretation of observed non-circular motions of gas and stars in circumnuclear (one kiloparsec- scale) regions. We have shown first of all that these motions are caused by a gravitational potential of large-scale bar. NGC3368 and NGC3786 have nuclear bars only, the...

  18. Gas-phase Oxygen Abundances and Radial Metallicity Gradients in the Two nearby Spiral Galaxies NGC 7793 and NGC 4945

    Science.gov (United States)

    Stanghellini, Letizia; Magrini, Laura; Casasola, Viviana

    2015-10-01

    Gas-phase abundances in H ii regions of two spiral galaxies, NGC 7793 and NGC 4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8 m Gemini South telescope. We found that NGC 7793 has a well-defined gas-phase radial oxygen gradient of -0.321 ± 0.112 dex {R}25-1 (or -0.054 ± 0.019 dex kpc-1) in the galactocentric range 0.17 < RG/R25 < 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC 4945, -0.253 ± 0.149 dex {R}25-1 (or -0.019 ± 0.011 dex kpc-1) for 0.04 < RG/R25 < 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC 7793 and NGC 4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC 7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC 4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an active galactic nucleus combined with a bar in the central regions of NGC 4945, and to its interacting environment.

  19. Internal kinematics of spiral galaxies in distant clusters IV. Gas kinematics of spiral galaxies in intermediate redshift clusters and in the field

    CERN Document Server

    Kutdemir, Elif; Peletier, Reynier; Da Rocha, Cristiano; Boehm, Asmus; Verdugo, Miguel

    2010-01-01

    (Abridged) We trace the interaction processes of galaxies at intermediate redshift by measuring the irregularity of their ionized gas kinematics, and investigate these irregularities as a function of the environment (cluster versus field) and of morphological type (spiral versus irregular). Our sample consists of 92 distant galaxies. 16 cluster (z~0.3 and z~0.5) and 29 field galaxies (mean z=0.44) of these have velocity fields with sufficient signal to be analyzed. We find that the fraction of galaxies that have irregular gas kinematics is remarkably similar in galaxy clusters and in the field at intermediate redshifts. The distribution of the field and cluster galaxies in (ir)regularity parameters space is also similar. On the other hand galaxies with small central concentration of light, that we see in the field sample, are absent in the cluster sample. We find that field galaxies at intermediate redshifts have more irregular velocity fields as well as more clumpy and less centrally concentrated light distr...

  20. Scalar potential model of spiral galaxy HI rotation curves and rotation curve asymmetry

    CERN Document Server

    Hodge, J C

    2006-01-01

    A scalar potential model (SPM) was developed from considerations of galaxy clusters and of redshift. The SPM is applied to HI rotation curves (RCs) and RC asymmetry of spiral galaxies. The resulting model adds the force of a scalar potential of the host galaxy and of neighboring galaxies to the Newtonian rotation velocity equation. The RC is partitioned radially into regions. The form of the equation for each parameter of each region is the same with differing proportionality constants. Integer values of each equation are determined empirically for each galaxy. Among the sample galaxies, the global properties of galaxies of B band luminosity, of position, and of orientation determine the RC and RC asymmetry. The Source of the scalar field acts as a monopole at distances of a few kpc from the centre of spiral galaxies. The scalar potential field causes Newtonian mechanics to considerably underestimate the mass in galaxies, which is the ``missing mass problem''. The SPM is consistent with RC and RC asymmetry ob...

  1. SPIN ALIGNMENTS OF SPIRAL GALAXIES WITHIN THE LARGE-SCALE STRUCTURE FROM SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youcai; Yang, Xiaohu; Luo, Wentao [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Lei [Purple Mountain Observatory, The Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: yczhang@shao.ac.cn, E-mail: xyang@sjtu.edu.cn [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  2. Quasars Lensed by Globular Clusters of Spiral and Elliptical Galaxies

    OpenAIRE

    Bukhmastova, Yu. L.

    2007-01-01

    Based on the SDSS catalog, we have found new close quasar-galaxy pairs. Quasars projected onto the halos of nearer galaxies are encountered among the multitude of quasars observed at various distances from us. Among them there are quasars that are close to the galaxies not only in angular separation, but also in redshift. Such quasar-galaxy pairs are called close pairs. We developed further the hypothesis that such pairs appear, because the fluxer on the nucleus of the more distant galaxy pas...

  3. The 2X-HI disks of spiral galaxies

    CERN Document Server

    Koribalski, B S

    2016-01-01

    The outskirts of galaxies - especially the very extended HI disks of galaxies - are strongly affected by their local environment. I highlight the giant 2X-HI disks of nearby galaxies (M 83, NGC 3621, and NGC 1512), studied as part of the Local Volume HI Survey (LVHIS), their kinematics and relation to XUV disks, signatures of tidal interactions and accretion events, the MHI - DHI relation as well as the formation of tidal dwarf galaxies. - Using multi-wavelength data, I create 3D visualisations of the gas and stars in galaxies, with the shape of their warped disks obtained through kinematic modelling of their HI velocity fields.

  4. Gravitational collapse in dust lanes and the appearance of spiral structure in galaxies

    International Nuclear Information System (INIS)

    We consider the possibility that there are two fundamental types of spirals in each spiral galaxy: one results from a spiral density wave, and the other is a stochastic spiral produced by the shear of self-propagating star formation events. It is proposed that there is a physical and causal connection between these two spirals, with the role of intermediary played by the dust lanes, which we assume to be shocked interstellar matter. We show that dust lanes should continuously collapse and fragment into massive cloud complexes by the action of their self-gravitational forces. The origin of the molecular ring at 5--6 kpc from the galactic center seems to be the result of a sharp minimum in the opposition to dust lane collapse by galactic tidal forces at these radii. When the resulting clouds begin to form stars (probably by an independent process), the pressures generated by their own OB associations will push them away from their star clusters and cause them to be shuffled around randomly in the region of the galaxy that lies ahead of the dust lane. Massive star formation may occur in the same clouds on numerous occasions, but they will have a different location each time. This shuffling will not only produce the appearance of a stochastic arm of young, star-forming sites (superposed on the underlying spiral), but it will also give the required stability to the numerical calculations of Gerola and Seiden, when combined with the assumption of a steady state cloud population for the whole galaxy. Numerous observational examples of these processes are cited for our own Galaxy and for other galaxies

  5. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. I. Discovery of low surface brightness systems around nearby spiral galaxies

    Science.gov (United States)

    Javanmardi, B.; Martinez-Delgado, D.; Kroupa, P.; Henkel, C.; Crawford, K.; Teuwen, K.; Gabany, R. J.; Hanson, M.; Chonis, T. S.; Neyer, F.

    2016-04-01

    Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims: The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 ≲ μe ≲ 28.8 mag arcsec-2 and are fit with Sersic profiles with indices n ≲ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges -15.6 ≲ Mr ≲ -7.8, 160 pc ≲ Re ≲ 4.1 kpc, and 0.1 × 106 ≲ (L/L⊙)r ≲ 127 × 106, respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions: Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

  6. 21 centimeter study of spiral galaxies in the Coma supercluster. II. Evidence for ongoing gas stripping in five cluster galaxies

    International Nuclear Information System (INIS)

    High-sensitivity 21 cm observations of 73 galaxies in the Coma supercluster are presented. Seventeen new redshifts are reported. Three galaxies in A1367 and two in the Coma Cluster are found with remarkably asymmetrical H I spectra indicating uneven gas distribution in their disks. This unstable configuration is interpreted as being due to ongoing dynamical gas stripping taking place on time scales shorter than those required for differential rotation to redistribute the gas, i.e., a few times 100 million yr. This suggests that spiral galaxies are continuously supplied to the clusters from the surrounding supercluster. 33 refs

  7. H-$\\alpha$ Imaging of Early-type(Sa-Sab) Spiral Galaxies, 1

    CERN Document Server

    Hameed, S A; Hameed, Salman; Devereux, Nick

    1999-01-01

    H-alpha and continuum images are presented for 27 nearby early-type(Sa-Sab) spiral galaxies. Contrary to popular perception, the images reveal copious massive star formation in some of these galaxies. A determination of the H-alpha morphology and a measure of the H-alpha luminosity suggests that early-type spirals can be classified into two broad categories based on the luminosity of largest HII region in the disk. The first category includes galaxies for which the individual HII regions have L(H-alpha) 10^(39) erg/s. All category 2 galaxies show either prominent dust lanes or other morphological peculiarities such as tidal tails which suggests that the anomalously luminous HII regions in category 2 galaxies may have formed as a result of a recent interaction. The observations, which are part of an on-going H-alpha survey, reveal early-type spirals to be a heterogeneous class of galaxies that are evolving in the current epoch. We have also identified some systematic differences between the classifications of...

  8. ARM AND INTERARM STAR FORMATION IN SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    We investigate the relationship between spiral arms and star formation in the grand-design spirals NGC 5194 and NGC 628 and in the flocculent spiral NGC 6946. Filtered maps of near-IR (3.6 μm) emission allow us to identify 'arm regions' that should correspond to regions of stellar mass density enhancements. The two grand-design spirals show a clear two-armed structure, while NGC 6946 is more complex. We examine these arm and interarm regions, looking at maps that trace recent star formation-far-ultraviolet (GALEX NGS) and 24 μm emission (Spitzer SINGS)-and cold gas-CO (HERACLES) and H I (THINGS). We find the star formation tracers and CO more concentrated in the spiral arms than the stellar 3.6 μm flux. If we define the spiral arms as the 25% highest pixels in the filtered 3.6 μm images, we find that the majority (60%) of star formation tracers occur in the interarm regions; this result persists qualitatively even when considering the potential impact of finite data resolution and diffuse interarm 24 μm emission. Even with a generous definition of the arms (45% highest pixels), interarm regions still contribute at least 30% to the integrated star formation rate (SFR) tracers. We look for evidence that spiral arms trigger star or cloud formation using the ratios of SFR (traced by a combination of FUV and 24 μm emission) to H2 (traced by CO) and H2 to H I. Any enhancement of SFR/M(H2) in the arm region is very small (less than 10%) and the grand-design spirals show no enhancement compared to the flocculent target. Arm regions do show a weak enhancement in H2/H I compared to the interarm regions, but at a fixed gas surface density there is little clear enhancement in the H2/H I ratio in the arm regions. Thus, it seems that spiral arms may only act to concentrate the gas to higher densities in the arms.

  9. Disc colours in field and cluster spiral galaxies at 0.5 < z < 0.8

    CERN Document Server

    Cantale, Nicolas; Courbin, Frederic; Rudnick, Gregory; Zaritsky, Dennis; Meylan, Georges; Desai, Vandana; De Lucia, Gabriella; Aragon-Salamanca, Alfonso; Poggianti, Bianca M; Finn, Rose; Simard, Luc

    2016-01-01

    We present a detailed study of the colours in late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 < z < 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolve their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1 sigma of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cor...

  10. Formation of S0 galaxies through mergers: Explaining angular momentum and concentration change from spirals to S0s

    CERN Document Server

    Querejeta, Miguel; Tapia, Trinidad; Borlaff, Alejandro; van de Ven, Glenn; Lyubenova, Mariya; Martig, Marie; Falcón-Barroso, Jesús; Méndez-Abreu, Jairo

    2015-01-01

    The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major mergers can provide an alternative way to transform spirals into S0s by analysing the spiral-spiral major mergers from the GalMer database that lead to realistic, relaxed S0-like galaxies. We find that the change in stellar angular momentum and concentration can explain the differences in the $\\lambda_\\mathrm{Re}$--$R_{90}/R_{50}$ plane found by the CALIFA team. Major mergers thus offer a feasible explanation for the transformation of spirals into S0s.

  11. Chemical evolution of spiral galaxies: models with star formation proportional to molecular hydrogen

    OpenAIRE

    Tosi, M.; Angeles I. Díaz

    1990-01-01

    This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Tosi, M., Díaz, A.I. Chemical evolution of spiral galaxies: models with star formation proportional to molecular hydrogen. Monthly Notices of the Royal Astronomical Society 246 (1990): 616-623

  12. Galaxy Zoo: the effect of bar-driven fueling on the presence of an active galactic nucleus in disc galaxies

    CERN Document Server

    Galloway, Melanie A; Fortson, Lucy F; Cardamone, Carolin N; Schawinski, Kevin; Cheung, Edmond; Lintott, Chris J; Masters, Karen L; Melvin, Thomas; Simmons, Brooke D

    2015-01-01

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19,756 disc galaxies at $0.01bar. Within this sample, AGN host galaxies have a higher overall percentage of bars (51.8%) than inactive galaxies exhibiting central star formation (37.1%). This difference is primarily due to known effects; that the presence of both AGN and galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16% of the average barred AGN fraction. Using the $L_{\\rm...

  13. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    OpenAIRE

    Puerari, Ivânio; Elmegreen, Bruce G.; Block, David L.

    2014-01-01

    We examine $8\\mu$m IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of $(\\ln R, \\theta)$ space and logarithmic spirals with various pitch angles. The diameter of the windo...

  14. Long-Lived Spiral Structure for Galaxies with Intermediate Size Bulges

    CERN Document Server

    Saha, Kanak

    2016-01-01

    Spiral structure in disk galaxies is modeled with nine collisionless N-body simulations including live disks, halos, and bulges with a range of masses. Two of these simulations make long-lasting and strong two-arm spiral wave modes that last for $\\sim5$ Gyr with constant pattern speed. These two had a light stellar disk and the largest values of the Toomre $Q$ parameter in the inner region at the time the spirals formed, suggesting the presence of a Q-barrier to wave propagation resulting from the bulge. The relative bulge mass in these cases is about 10\\%. Models with weak two-arm spirals had pattern speeds that followed the radial dependence of the Inner Lindblad Resonance.

  15. INTEGRAL-FIELD STELLAR AND IONIZED GAS KINEMATICS OF PECULIAR VIRGO CLUSTER SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion σ, and the ionized gas velocity (Hβ and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter λ R. An evaluation of the galaxies in the λ R ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact Hα morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects

  16. A close nuclear black-hole pair in the spiral galaxy NGC 3393.

    Science.gov (United States)

    Fabbiano, G; Wang, Junfeng; Elvis, M; Risaliti, G

    2011-09-22

    The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution. PMID:21881560

  17. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphology

    CERN Document Server

    Willett, Kyle W; Simmons, Brooke D; Masters, Karen L; Skibba, Ramin A; Kaviraj, Sugata; Melvin, Thomas; Wong, O Ivy; Nichol, Robert C; Cheung, Edmond; Lintott, Chris J; Fortson, Lucy

    2015-01-01

    We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z1. Of the galaxies lying significantly above the M-SFR relation in the local Universe, more than 50% are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

  18. Bulge-Disk Decomposition of 659 Spiral and Lenticular Galaxy Brightness Profiles

    OpenAIRE

    Baggett, W. E.; Baggett, S. M.; Anderson, K. S. J.

    1998-01-01

    We present one of the largest homogeneous sets of spiral and lenticular galaxy brightness profile decompositions completed to date. The 659 galaxies in our sample have been fitted with a deVaucouleurs' law for the bulge component and an inner-truncated exponential for the disk component. Of the 659 galaxies in the sample, 620 were successfully fit with the chosen fitting functions. The fits are generally well-defined, with more than 90% having RMS deviations from the observed profile of less ...

  19. The environmental dependence of the structure of outer galactic discs in STAGES spiral galaxies

    CERN Document Server

    Maltby, David T; Aragón-Salamanca, Alfonso; Wolf, Christian; Bell, Eric F; Jogee, Shardha; Haeussler, Boris; Barazza, Fabio D; Boehm, Asmus; Jahnke, Knud

    2011-01-01

    We present an analysis of V-band radial surface brightness profiles for spiral galaxies from the field and cluster environments using Hubble Space Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~330 face-on to intermediately inclined spiral galaxies and assess the effect of the galaxy environment on the azimuthally averaged radial surface brightness mu profiles for each galaxy in the outer stellar disc (24 < mu < 26.5 mag per sq arcsec). For galaxies with a purely exponential outer disc (~50 per cent), we determine the significance of an environmental dependence on the outer disc scalelength h_out. For galaxies with a broken exponential in their outer disc, either down-bending (truncation, ~10 per cent) or up-bending (anti-truncation, ~40 per cent), we measure the strength T (outer-to-inner scalelength ratio, log_10(h_out/h_in) of the mu breaks and determine the significance of an environmental dependence ...

  20. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    CERN Document Server

    Greene, Jenny E; Kim, Minjin; Laesker, Ronald; Goulding, Andy D; Gao, Feng; Braatz, James A; Henkel, Christian; Condon, James; Lo, Fred K Y; Zhao, Wei

    2016-01-01

    We use new precision measurements of black hole masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive black hole (BH) mass. The megamaser-derived BH masses span 10^6-10^8 M_sun, while all the galaxy properties that we examine (including stellar mass, central mass density, central velocity dispersion) lie within a narrow range. Thus, no galaxy property correlates tightly with M_BH in ~L* spiral galaxies. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed sigma* the mean megamaser M_BH are offset by -0.6+/-0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to inability to resolve the spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  1. The JCMT Nearby Galaxies Legacy Survey II: Warm Molecular Gas and Star Formation in Three Field Spiral Galaxies

    CERN Document Server

    Warren, B E; Israel, F P; Serjeant, S; Bendo, G J; Brinks, E; Clements, D L; Irwin, J A; Knapen, J H; Leech, J; Matthews, H E; Mühle, S; Mortimer, A M J; Petitpas, G; Sinukoff, E; Spekkens, K; Tan, B K; Tilanus, R P J; Usero, A; van der Werf, P P; Vlahakis, C; Wiegert, T; Zhu, M

    2010-01-01

    We present the results of large-area CO J=3-2 emission mapping of three nearby field galaxies, NGC 628, NGC 3521, and NGC 3627, completed at the James Clerk Maxwell Telescope as part of the Nearby Galaxies Legacy Survey. These galaxies all have moderate to strong CO J=3-2 detections over large areas of the fields observed by the survey, showing resolved structure and dynamics in their warm/dense molecular gas disks. All three galaxies were part of the Spitzer Infrared Nearby Galaxies Survey sample, and as such have excellent published multi-wavelength ancillary data. These data sets allow us to examine the star formation properties, gas content, and dynamics of these galaxies on sub-kiloparsec scales. We find that the global gas depletion times for dense/warm molecular gas in these galaxies is consistent with other results for nearby spiral galaxies, indicating this may be independent of galaxy properties such as structures, gas compositions, and environments. Similar to the results from the THINGS HI survey,...

  2. AN Hα NUCLEAR SPIRAL STRUCTURE IN THE E0 ACTIVE GALAXY Arp 102B

    International Nuclear Information System (INIS)

    We report the discovery of a two-armed mini-spiral structure within the inner kiloparsec of the E0 LINER/Seyfert 1 galaxy Arp 102B. The arms are observed in Hα emission and located east and west of the nucleus, extending up to ∼1 kpc from it. We use narrow-band imaging from the Hubble Space Telescope Advanced Camera for Surveys, in combination with archival Very Large Array radio images at 3.6 and 6 cm to investigate the origin of the nuclear spiral. From the Hα luminosity of the spiral, we obtain an ionized gas mass of the order of 106 solar masses. One possibility is that the nuclear spiral represents a gas inflow triggered by a recent accretion event which has replenished the accretion disk, giving rise to the double-peaked emission-line profiles characteristic of Arp 102B. However, the radio images show a one-sided curved jet which correlates with the eastern spiral arm observed in the Hα image. A published milliarcsecond radio image also shows a one-sided structure at position angle ∼400, approximately aligned with the inner part of the eastern spiral arm. The absence of a radio counterpart to the western spiral arm is tentatively interpreted as indicating that the jet is relativistic, with an estimated speed of 0.45c. Estimates of the jet kinetic energy and the ionizing luminosity of the active nucleus indicate that both are capable of ionizing the gas along the spiral arms. We conclude that, although the gas in the nuclear region may have originated in an accretion event, the mini spiral is most likely the result of a jet-cloud interaction rather than an inflowing stream.

  3. The surface brightness of spiral galaxies: Pt. 4

    International Nuclear Information System (INIS)

    Using measurements from IRAS correlations are found between optical surface brightness and both infrared-to-optical flux ratio and infrared colour temperature, in the sense that galaxies with high surface brightness have higher FIR emission and higher temperatures. (author)

  4. The Soft X-Ray Emission Component of Spiral Galaxies

    Science.gov (United States)

    Fabbiano, Giuseppina

    1998-01-01

    Work included the analysis of the HRJ observations of the Sombrero galaxy (Fabbiano and Juda) published in Ap.J. This paper discussed the discovery of a point-like x-ray source at the nucleus of the galaxy, which is suspected to host a massive black hole. More work was done on the analysis of the Observation of M94 in support of an AXAF proposal. We have also analyzed the M81 data by adding to our observation the entire set of the archival ROSAT data. We plan to write up the results for publication. Both galaxies have nuclei optically similar to that of the Sombrero galaxy. The nucleus of M81 is a known x-ray source. The M94 data has revealed a point-like nuclear source superposed on more diffuse emission.

  5. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    International Nuclear Information System (INIS)

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10° to 60°. Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately ∼20°, the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than ∼20° would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than ∼50°, chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is ∼50°.

  6. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.; Peimbert, A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, A.P. 70-264, 04510 Mexico D.F. (Mexico); Velazquez, H. M., E-mail: barbara@astroscu.unam.mx [Observatorio Astronomico Nacional, Universidad Nacional Autonoma de Mexico, Apdo. Postal 877, 22800 Ensenada (Mexico)

    2012-01-20

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10 Degree-Sign to 60 Degree-Sign . Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately {approx}20 Degree-Sign , the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than {approx}20 Degree-Sign would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than {approx}50 Degree-Sign , chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is {approx}50 Degree-Sign .

  7. Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms

    Science.gov (United States)

    2004-06-01

    Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the

  8. Galaxy Zoo: the effect of bar-driven fuelling on the presence of an active galactic nucleus in disc galaxies

    Science.gov (United States)

    Galloway, Melanie A.; Willett, Kyle W.; Fortson, Lucy F.; Cardamone, Carolin N.; Schawinski, Kevin; Cheung, Edmond; Lintott, Chris J.; Masters, Karen L.; Melvin, Thomas; Simmons, Brooke D.

    2015-04-01

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19 756 disc galaxies at 0.01 < z < 0.05 which have been visually examined for the presence of a bar. Within this sample, AGN host galaxies have a higher overall percentage of bars (51.8 per cent) than inactive galaxies exhibiting central star formation (37.1 per cent). This difference is primarily due to known effects: that the presence of both AGN and galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16 per cent of the average barred AGN fraction. Using the L_{[O III]}/MBH ratio as a measure of AGN strength, we show that barred AGNs do not exhibit stronger accretion than unbarred AGNs at a fixed mass and colour. The data are consistent with a model in which bar-driven fuelling does contribute to the probability of an actively growing black hole, but in which other dynamical mechanisms must contribute to the direct AGN fuelling via smaller, non-axisymmetric perturbations.

  9. Model of Outgrowths in the Spiral Galaxies NGC 4921 and NGC 7049 and the Origin of Spiral Arms

    CERN Document Server

    Carlqvist, Per

    2012-01-01

    NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H II regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account f...

  10. Reconstructing magnetic fields of spiral galaxies from radiopolarimetric observations

    Science.gov (United States)

    Shneider, C.

    2015-12-01

    We live in a magnetic universe with magnetic fields spanning an enormous range of spatial and temporal scales. In particular, magnetic fields at the scale of a galaxy are known as galactic magnetic fields and are the focus of this PhD thesis. These galactic magnetic fields are very important since they affect the dynamics of the interstellar gas as well as the gas distribution. The presence of these magnetic fields induces a certain type of radiation to occur at radio frequencies known as synchrotron radiation. The observed polarization properties of this synchrotron radiation then serves to record the imprint of these magnetic fields. The goal of this thesis has been to infer the structure of the magnetic field across various spatial scales in our own Galaxy as well as the strength and structure of the magnetic field in other galaxies using radiopolarimetric observations.

  11. Integral-Field Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Spiral Galaxies

    CERN Document Server

    Cortés, J R; Hardy, E

    2014-01-01

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5-meter telescope, to seek kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. 2-Dimensional maps of the stellar velocity $V$, and stellar velocity dispersion $\\sigma$ and the ionized gas velocity (H$\\beta$ and/or [\\ion{O}{3}]) are presented for galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axis are found in several galaxies. While in some cases this is due to a bar, in other cases it seems associated with a gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxi...

  12. MOND rotation curves of very low mass spiral galaxies

    OpenAIRE

    Milgrom, Mordehai; Sanders, Robert H.

    2006-01-01

    We present MOND analysis for several of the lowest mass disc galaxies currently amenable to such analysis--with (baryonic) masses below 4x10^8 solar masses. The agreement is good, extending the validity of MOND and its predicted mass velocity relation, to such low masses.

  13. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    CERN Document Server

    Michtchenko, Tatiana A; Barros, Douglas A; Lépine, Jacques R D

    2016-01-01

    Context: Resonances in the stellar orbital motion under perturbations from spiral arms structure play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (for nearly circular orbits), but is not suitable in general. Aims: To expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped profiles, without any restriction on the stellar orbital configurations, and expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes are constructed numerically, in order to characterize the phase-space structure and identify the precise location of the resonances. The study is complemented by the construction of dynamical power spectra, which provide the identif...

  14. The JCMT nearby galaxies legacy survey - X. Environmental effects on the molecular gas and star formation properties of spiral galaxies

    Science.gov (United States)

    Mok, Angus; Wilson, C. D.; Golding, J.; Warren, B. E.; Israel, F. P.; Serjeant, S.; Knapen, J. H.; Sánchez-Gallego, J. R.; Barmby, P.; Bendo, G. J.; Rosolowsky, E.; van der Werf, P.

    2016-03-01

    We present a study of the molecular gas properties in a sample of 98 H I - flux selected spiral galaxies within ˜25 Mpc, using the CO J = 3 - 2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H2 mass in the Virgo galaxies, despite their lower mean H I mass. This leads to a significantly higher H2 to H I ratio for Virgo galaxies. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H2 masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative of differences in the star formation process between low- and high-mass galaxies, and a negative correlation between the molecular gas depletion time and the specific star formation rate.

  15. The discovery of seven extremely low surface brightness galaxies in the field of the nearby spiral galaxy M101

    CERN Document Server

    Merritt, Allison; Abraham, Roberto

    2014-01-01

    Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of \\(10 - 30\\) arcseconds and central surface brightnesses of \\(\\mu_{g} \\sim 25.5 - 27.5\\) mag arcsec\\(^{-2}\\). Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range \\(-11.6 \\lesssim M_{V} \\lesssim -9.3\\) and their effective radii are \\(350\\) pc \\(-\\) \\(1.3\\) kpc. Their radial surface brightness profiles ar...

  16. BULGE AND CLUMP EVOLUTION IN HUBBLE ULTRA DEEP FIELD CLUMP CLUSTERS, CHAINS AND SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Clump clusters and chain galaxies in the Hubble Ultra Deep Field (UDF) are examined for bulges in Near-Infrared Camera Multi-Object Spectrometer images. Approximately 50% of the clump clusters and 30% of the chains have relatively red and massive clumps that could be young bulges. Magnitudes and colors are determined for these bulgelike objects and for the bulges in spiral galaxies, and for all of the prominent star formation clumps in these three galaxy types. The colors are fitted to population evolution models to determine the bulge and clump masses, ages, star formation rate decay times, and extinctions. The results indicate that bulgelike objects in clump clusters and chain galaxies have similar ages and two to five times larger masses compared to the star formation clumps, while the bulges in spirals have roughly six times larger ages and 20 to 30 times larger masses than the clumps. All systems appear to have an underlying red disk population. The masses of star-forming clumps are typically in a range from 107 to 108 M sun; their ages have a wide range around ∼102 Myr. Ages and extinctions both decrease with redshift. Star formation is probably the result of gravitational instabilities in the disk gas, in which case the large clump mass in the UDF is the result of a high gas velocity dispersion, 30 km s-1 or more, combined with a high gas mass column density, ∼100 M sun pc-2. Because clump clusters and chains dominate disk galaxies beyond z ∼ 1, the observations suggest that these types represent an early phase in the formation of modern spiral galaxies, when the bulge and inner disk formed.

  17. Megaparsec relativistic jets launched from an accreting supermassive black hole in an extreme spiral galaxy

    International Nuclear Information System (INIS)

    The radio galaxy phenomenon is directly connected to mass-accreting, spinning supermassive black holes found in the active galactic nuclei. It is still unclear how the collimated jets of relativistic plasma on hundreds to thousands of kiloparsec scales form and why they are nearly always launched from the nuclei of bulge-dominated elliptical galaxies and not flat spirals. Here we present the discovery of the giant radio source J2345–0449 (z = 0.0755), a clear and extremely rare counterexample where relativistic jets are ejected from a luminous and massive spiral galaxy on a scale of ∼1.6 Mpc, the largest known so far. Extreme physical properties observed for this bulgeless spiral host, such as its high optical and infrared luminosity, large dynamical mass, rapid disk rotation, and episodic jet activity, are possibly the results of its unusual formation history, which has also assembled, via gas accretion from a disk, its central black hole of mass >2 × 108 M ☉. The very high mid-IR luminosity of the galaxy suggests that it is actively forming stars and still building a massive disk. We argue that the launch of these powerful jets is facilitated by an advection-dominated, magnetized accretion flow at a low Eddington rate onto this unusually massive (for a bulgeless disk galaxy) and possibly fast spinning central black hole. Therefore, J2345–0449 is an extremely rare, unusual galactic system whose properties challenge the standard paradigms for black hole growth and the formation of relativistic jets in disk galaxies. Thus, it provides fundamental insight into accretion disk-relativistic jet coupling processes.

  18. Properties of Disks and Bulges of Spiral and Lenticular Galaxies in the Sloan Digital Sky Survey

    CERN Document Server

    Oohama, N; Fukugita, M; Yasuda, N; Nakamura, O

    2009-01-01

    A bulge-disk decomposition is made for 737 spiral and lenticular galaxies drawn from a SDSS galaxy sample for which morphological types are estimated. We carry out the bulge-disk decomposition using the growth curve fitting method. It is found that bulge properties, effective radius, effective surface brightness, and also absolute magnitude, change systematically with the morphological sequence; from early to late types, the size becomes somewhat larger, and surface brightness and luminosity fainter. In contrast disks are nearly universal, their properties remaining similar among disk galaxies irrespective of detailed morphologies from S0 to Sc. While these tendencies were often discussed in previous studies, the present study confirms them based on a large homogeneous magnitude-limited field galaxy sample with morphological types estimated. The systematic change of bulge-to-total luminosity ratio, $B/T$, along the morphological sequence is therefore not caused by disks but mostly by bulges. It is also shown ...

  19. Old Star Clusters in Spiral Galaxies: M101 as a Case Study

    Science.gov (United States)

    Simanton, Lesley Ann

    2015-01-01

    Most stars form in groups and clusters, at least a small fraction of which can be extremely long-lived. However, many details of how star clusters form and how they disrupt are still unclear. We present and examine a catalog of old star clusters in the nearby spiral galaxy M101, and compare with the known properties of old star clusters in other spiral galaxies. Data include multi-band Hubble Space Telescope images and Gemini-GMOS spectra. Among the properties examined are luminosity distributions, colors, sizes, spatial distributions, and velocities. We highlight the somewhat surprising result of a population of old, disk clusters in M101, which are unlike populations found in the Milky Way and M31.

  20. Star formation properties in barred galaxies (SFB) Ⅱ.NGC 2903 and NGC 7080

    Institute of Scientific and Technical Information of China (English)

    Zhi-Min Zhou; Chen Cao; Hong Wu

    2012-01-01

    Stellar bars are important for the secular evolution of disk galaxies because they can drive gas into the galactic central regions.To investigate the star formation properties in barred galaxies,we presented a multi-wavelength study of two barred galaxies:NGC 2903 and NGC 7080.We performed the three-component bulge-diskbar decomposition using the 3.6 μm images,and identified the bulges in the two galaxies as pseudobulges.Based on the narrowband Hα images,the star formation clumps were identified and analyzed.The clumps in the bulge regions have the highest surface densities of star formation rates in both galaxies,while the star formation activities in the bar of NGC 2903 are more intense than those in the bar of NGC 7080.Finally,we compared our results with the scenario of bar-driven secular evolution in previous studies,and discussed the possible evolutionary stages of the two galaxies.

  1. Bulge-Disk Decompositions and Structural Bimodality of Ursa Major Cluster Spiral Galaxies

    OpenAIRE

    McDonald, Michael; Courteau, Stephane; Tully, R. Brent

    2008-01-01

    We present bulge and disk (B/D) decompositions of existing K'-band surface brightness profiles for 65 Ursa Major cluster spiral galaxies. This improves upon the disk-only fits of Tully et al. (1996). The 1996 disk fits were used by Tully & Verheijen (1997) for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new 1D B/D decompositions yield disk structural parameters that differ only slightly from the basic fits of Tully et al. and ev...

  2. The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

    CERN Document Server

    Vollmer, B; Braine, J; Chung, A; Kenney, J D P

    2012-01-01

    The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies, possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the m...

  3. Pitch Angle Restrictions in Late Type Spiral Galaxies Based on Chaotic and Ordered Orbital Behavior

    CERN Document Server

    Perez-Villegas, Angeles; Moreno, Edmundo; Peimbert, Antonio; Velazquez, Hector M

    2011-01-01

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a 3-D self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, going from 10$\\deg$ to 60$\\deg$. Testing undirectly orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately $\\sim 20\\deg$, the response supports closely the potential permitting readily the presence of long lasting spiral structures. The density response tends to "avoid" larger pitch angles in the potential, by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than $\\sim 20\\deg$, would not be long-lasting structures but rather transient. On the other hand, from an extensive orbital study in phase space, we also find that for late type galaxies with pitch angles larger than $\\sim 50\\deg$, chaos becomes pervasive destroying the ordered phase space surrounding the main sta...

  4. Modelling the spectro-photometric and chemical evolution of Low Surface Brightness spiral galaxies

    OpenAIRE

    Hoek, L. B. van den; de Blok, W J G

    1995-01-01

    We investigate the star formation history and chemical evolution of Low Surface Brightness (LSB) spiral galaxies by means of their observed spectro-photometric and chemical properties. We present preliminary results for Johnson-Cousins UBVRI magnitudes and stellar [O/H] abundance ratios using a galactic chemical evolution model incorporating a detailed metallicity dependent set of stellar input data covering all relevant stages of stellar evolution. Comparison of our model results with observ...

  5. Radio continuum and far-infrared emission of spiral galaxies: Implications of correlations

    International Nuclear Information System (INIS)

    Researchers present a study extending the correlation seen between radio continuum and far-infrared emissions from spiral galaxies to a lower frequency of 408 MHz and also as a function of radio spectral index. The tight correlation seen between the two luminosities is then used to constrain several parameters governing the emissions such as the changes in star formation rate and mass function, frequency of supernovae that are parents of the interstellar electrons and factors governing synchrotron radio emission

  6. A catalog of planetary nebula candidates in the Sculptor spiral galaxy NGC 300

    OpenAIRE

    Pena, Miriam; Reyes-Perez, Jonnathan; Hernandez-Martinez, Liliana; Perez-Guillen, Miguel

    2012-01-01

    [OIII]5007 on-band off-band images, obtained with the VLT and FORS2 spectrograph in two zones (center and outskirts) of the spiral galaxy NGC300, are analyzed searching for emission line objects. In particular we search for planetary nebula (PN) candidates to analyze their distribution and luminosity properties, to perform follow-up spectroscopy, and to study the planetary nebula luminosity function, PNLF. In the continuum-subtracted images, a large number of emission line objects were detect...

  7. The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

    Science.gov (United States)

    Vollmer, B.; Wong, O. I.; Braine, J.; Chung, A.; Kenney, J. D. P.

    2012-07-01

    The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data based on the 8, 24, 70, and 160 μm data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies (NGC 4430, NGC 4501, and NGC 4522), possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the molecular gas content on the windward side of ram pressure-stripped galaxies is not observed. The ram-pressure stripped extraplanar gas of 3 highly inclined spiral galaxies (NGC 4330, NGC 4438, and NGC 4522) shows a depressed star formation efficiency with respect to the total gas, and one of them (NGC 4438) shows a depressed rate even with respect to the molecular gas. The interpretation is that stripped gas loses the gravitational confinement and associated pressure of the galactic disk, and the gas flow is diverging, so the gas density decreases and the star formation rate drops. We found two such regions of low star formation efficiency in the more face-on galaxies NGC 4501 and NGC 4654 which are both undergoing ram pressure stripping. These regions show low radio continuum emission or unusually steep radio spectral index. However, the stripped extraplanar gas in one highly inclined

  8. A Massive Spiral Galaxy in the Zone of Avoidance

    CERN Document Server

    Donley, J L; Koribalski, B S; Kraan-Korteweg, R C; Schröder, A; Staveley-Smith, L

    2006-01-01

    We report the discovery of a very HI-massive disk galaxy, HIZOA J0836-43, at a velocity of v_hel = 10689 km/s, corresponding to a distance of 148 Mpc (assuming H_0=75 km/s/Mpc). It was found during the course of a systematic HI survey of the southern Zone of Avoidance (|b| < 5 deg) with the multibeam system at the 64m Parkes radio telescope. Follow-up observations with the Australia Telescope Compact Array (ATCA) reveal an extended HI disk. We derive an HI mass of 7.5 x 10^10 Msun. Using the HI radius, we estimate a total dynamical mass of 1.4 x 10^12 Msun, similar to the most massive known disk galaxies such as Malin 1. HIZOA J0836-43 lies deep in the Zone of Avoidance (l, b = 262.48 deg, -1.64 deg) where the optical extinction is very high, A_B = 9.8. However, in the near-infrared wavebands, where the extinction is considerably lower, HIZOA J0836-43 is clearly detected by both DENIS and 2MASS. Deep AAT near-infrared (Ks and H-band) images show that HIZOA J0836-43 is an inclined disk galaxy with a promine...

  9. Magnetic fields and spiral arms in the galaxy M51

    CERN Document Server

    Fletcher, A; Shukurov, A; Berkhuijsen, E M; Horellou, C

    2010-01-01

    (Abridged) We use new multi-wavelength radio observations, made with the VLA and Effelsberg telescopes, to study the magnetic field of the nearby galaxy M51. We compare the spatial distribution of the radio emission with observations of the neutral gas, derive radio spectral index and Faraday depolarization maps, and model the large scale variation in Faraday rotation in order to deduce the structure of the regular magnetic field. We derive two components for the regular magnetic field in this galaxy: the disc is dominated by a combination of azimuthal modes, m=0+2, but in the halo only an m=1 mode is required to fit the observations. We suggest a simple method to estimate the turbulent scale in the magneto-ionic medium from the dependence of the standard deviation of the observed Faraday rotation measure on resolution. We thus obtain 50pc for the size of the turbulent eddies; to our knowledge, this is the first determination of the turbulent scale in an external galaxy. We disuss how the observed arm-interar...

  10. An Exploration of the Tully-Fisher Relation for Extreme Late-Type Spiral Galaxies

    CERN Document Server

    Matthews, L D; Gallagher, J S

    1998-01-01

    This paper explores the adherence of 47 extreme late-type galaxies to the B- and V-band Tully-Fisher relations defined by a sample of local calibrators. In both bands we find the mean luminosity at a given line width for extreme late-type spirals to lie below that predicted by standard Tully-Fisher relations. While many of the extreme late-type spirals do follow the Tully-Fisher relation to within our observational uncertainties, most of these galaxies lie below the normal, linear Tully-Fisher relation, and some are underluminous by more than 2 sigma (i.e. >1.16 magnitudes in V). This suggests a possible downward curvature of the Tully-Fisher relation for some of the smallest and faintest rotationally supported disk galaxies. This may be a consequence of the increasing prevalence of dark matter in these systems. We find the deviation from the Tully-Fisher relation to increase with decreasing luminosity and decreasing optical linear size in our sample, implying that the physically smallest and faintest spirals...

  11. GAMA/H-ATLAS: The Dust Opacity - Stellar Mass Surface Density Relation for Spiral Galaxies

    CERN Document Server

    Grootes, M W; Popescu, C C; Pastrav, B; Andrae, E; Gunawardhana, M; Kelvin, L S; Liske, J; Seibert, M; Taylor, E N; Graham, A W; Baes, M; Baldry, I K; Bourne, N; Brough, S; Cooray, A; Dariush, A; De Zotti, G; Driver, S P; Dunne, L; Gomez, H; Hopkins, A M; Hopwood, R; Jarvis, M; Loveday, J; Maddox, S; Madore, B F; Michałowski, M J; Norberg, P; Parkinson, H R; Prescott, M; Robotham, A S G; Smith, D J B; Thomas, D; Valiante, E

    2013-01-01

    We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, \\tau^f_B, and the stellar mass surface density, \\mu_{*}, of nearby (z < 0.13) spiral galaxies: log(\\tau^f_B) = 1.12(+-0.11)log(\\mu_{*}/M_sol kpc^2)-8.6(+-0.8). This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey and detected in the FIR/submm in the Herschel-ATLAS survey. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to \\mu_{*} we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and S'ersic-profile morphological fits. Considered together with previously established empirical relationships between stellar mass, metallicity and gas mass, the near linearity and high constant of proportionality of the \\tau^f_B-\\mu_{*} relation disfavors a stellar origin for the bulk of ref...

  12. Optical spectroscopy of the radio-loud nuclei of spiral galaxies: Starbursts or monsters

    International Nuclear Information System (INIS)

    We present optical spectroscopic data pertaining to the physical state, kinematics, and spatial extent of the emission-line gas near the radio-loud nuclei of spiral galaxies. These data are combined with published optical, radio, and infrared data to evaluate the suggestions by Condon et al. (1982) that the nuclear radio emission in this class of galaxy is produced by multiple supernova remnants generated as a consequence of a nuclear starburst. As a whole, the radio-loud nuclei have stronger emission lines than radio-quiet nuclei of galaxies of similar Hubble/de Vaucouleurs type. This emission-line gas is generally at least as spatially extended as the radio continuum emission. However, we find that only about 1/3 of the spiral galaxies examined have optical spectroscopic properties consistent with those of ''extranuclear starbursts'' (i.e., giant H II regions). The majority of the nuclei seem to require a form of energy input to the ionized gas which is ''harder'' than the Lyman continuum radiation of OB stars, as their emission-line spectra are of the Seyfert or Liner variety. The nuclei with H II region spectra are distinct from the nuclei with Seyfert spectra in terms of radio morphology and radio spectral index, and tend to occur in spiral galaxies of much later Hubble type than do the Seyfert or Liner nuclei (Sc vs Sa). Moreover, the most luminous nuclear radio sources in our sample (PMHz> or =1022 Watts Hz-1 Sr-1) are not associated with H II region nuclei. We summarize evidence that the putative nuclear starbursts must differ significantly from extranuclear starbursts

  13. The JCMT Nearby Galaxies Legacy Survey X. Environmental Effects on the Molecular Gas and Star Formation Properties of Spiral Galaxies

    CERN Document Server

    Mok, Angus; Golding, J; Warren, B E; Israel, F P; Serjeant, S; Knapen, J H; Sanchez-Gallego, J R; Barmby, P; Bendo, G J; Rosolowsky, E; van der Werf, P

    2015-01-01

    We present a study of the molecular gas properties in a sample of 98 HI - flux selected spiral galaxies within $\\sim25$ Mpc, using the CO $J=3-2$ line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H$_{2}$ mass in the Virgo galaxies, despite their lower mean HI mass. This leads to a significantly higher H$_{2}$ to HI ratio for Virgo galaxies. Combining our data with complementary H$\\alpha$ star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H$_{2}$ masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative...

  14. Rotation Curve and Mass Decomposition for the Edge-on Spiral Galaxy UGC 711

    Science.gov (United States)

    Mendelowitz, C. M.; Matthews, L. D.; Hibbard, J. E.; Wilcots, E. M.

    2000-12-01

    Superthin galaxies are examples of low surface brightness (LSB) spiral galaxies seen edge-on. These galaxies are gas-rich and exhibit diffuse, highly flattened stellar disks with little or no bulge component and extremely small stellar scale heights. One interesting property of many superthin galaxies is that they exhibit rotation curves that appear to rise slowly throughout their stellar disks. However, some recent work has suggested that observational effects (including projection, internal extinction, and beam smearing) may account for some or all of these slowly rising rotation curves. To explore this question, we utilize new HI 21-cm line data from the Very Large Array (VLA) and optical R- and B- band data from the WIYN telescope for the nearby superthin galaxy UGC 711. We derive an HI rotation curve, as well as global optical and HI properties for this galaxy, and show that it is consistent with an LSB galaxy seen edge-on. We also compare and contrast its properties with the superthin UGC 7321, as recently studied by Matthews et al. (1999, AJ, 118, 2751). Even after taking into account beam smearing and projection effects, we find the rotation curve of UGC 711 continues to rise slowly to the last measured point. Using the observed light and HI profiles, we decompose the rotation curve into the contributions from stars, gas, and dark matter. We find that the slowly rising velocity curve requires a significant dark matter contribution at all radii.

  15. Kinematic Evolution of Field and Cluster Spiral Galaxies

    OpenAIRE

    Ziegler, Bodo; Boehm, Asmus

    2014-01-01

    We investigate the evolution of the Tully-Fisher relation out to z=1 with 137 emission-line galaxies in the field that display a regular rotation curve. They follow a linear trend with lookback time being on average brighter by 1.1Bmag and 60% smaller at z=1. For a subsample of 48 objects with very regular gas kinematics and stellar structure we derive a TF scatter of 1.15mag, which is two times larger than local samples exhibit. This is probably due to modest variations in their star formati...

  16. WHICH GALAXIES HOST BARS AND DISKS? A STUDY OF THE COMA CLUSTER

    International Nuclear Information System (INIS)

    We present a study of the bar fraction in the Coma Cluster galaxies based on a sample of ∼190 galaxies selected from the Sloan Digital Sky Survey Data Release 6 and observed with the Hubble Space Telescope (HST) Advanced Camera for Survey (ACS). The unprecedented resolution of the HST-ACS images allows us to explore the presence of bars, detected by visual classification, throughout a luminosity range of 9 mag (-23 ∼r ∼r ∼9∼*/Modot∼11). This result holds when compared with a sample of bright/massive field galaxies. In addition, we find that the bar fraction does not vary significantly when going from the center to the cluster outskirts, implying that cluster environment plays a second-order role in bar formation/evolution. The shape of the bar fraction distribution with respect to both luminosity and mass is well matched by the luminosity distribution of disk galaxies in Coma, indicating that bars are good tracers of cold stellar disks. We discuss the implications of our results for the formation and evolution scenarios of bars and disks.

  17. Simulating a slow bar in the low surface brightness galaxy UGC 628

    Science.gov (United States)

    Chequers, Matthew H.; Spekkens, Kristine; Widrow, Lawrence M.; Gilhuly, Colleen

    2016-08-01

    We present a disc-halo N-body model of the low surface brightness galaxy UGC 628, one of the few systems that harbours a "slow" bar with a ratio of corotation radius to bar length of mathcal {R} equiv R_c/a_b ˜ 2. We select our initial conditions using SDSS DR10 photometry, a physically motivated radially variable mass-to-light ratio profile, and rotation curve data from the literature. A global bar instability grows in our submaximal disc model, and the disc morphology and dynamics agree broadly with the photometry and kinematics of UGC 628 at times between peak bar strength and the onset of buckling. Prior to bar formation, the disc and halo contribute roughly equally to the potential in the galaxy's inner region, giving the disc enough self gravity for bar modes to grow. After bar formation there is significant mass redistribution, creating a baryon dominated inner and dark matter dominated outer disc. This implies that, unlike most other low surface brightness galaxies, UGC 628 is not dark matter dominated everywhere. Our model nonetheless implies that UGC 628 falls on same the relationship between dark matter fraction and rotation velocity found for high surface brightness galaxies, and lends credence to the argument that the disc mass fraction measured at the location where its contribution to the potential peaks is not a reliable indicator of its dynamical importance at all radii.

  18. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    CERN Document Server

    Puerari, Ivânio; Block, David L

    2014-01-01

    We examine $8\\mu$m IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of $(\\ln R, \\theta)$ space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from ...

  19. Hα3: an Hα imaging survey of HI selected galaxies from ALFALFA. VI. The role of bars in quenching star formation from z = 3 to the present epoch

    Science.gov (United States)

    Gavazzi, G.; Consolandi, G.; Dotti, M.; Fanali, R.; Fossati, M.; Fumagalli, M.; Viscardi, E.; Savorgnan, G.; Boselli, A.; Gutiérrez, L.; Hernández Toledo, H.; Giovanelli, R.; Haynes, M. P.

    2015-08-01

    A growing body of evidence indicates that the star formation rate per unit stellar mass (sSFR) decreases with increasing mass in normal main-sequence star-forming galaxies. Many processes have been advocated as being responsible for this trend (also known as mass quenching), e.g., feedback from active galactic nuclei (AGNs), and the formation of classical bulges. In order to improve our insight into the mechanisms regulating the star formation in normal star-forming galaxies across cosmic epochs, we determine a refined star formation versus stellar mass relation in the local Universe. To this end we use the Hα narrow-band imaging follow-up survey (Hα3) of field galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Coma and Local superclusters. By complementing this local determination with high-redshift measurements from the literature, we reconstruct the star formation history of main-sequence galaxies as a function of stellar mass from the present epoch up to z = 3. In agreement with previous studies, our analysis shows that quenching mechanisms occur above a threshold stellar mass Mknee that evolves with redshift as ∝ (1 + z)2. Moreover, visual morphological classification of individual objects in our local sample reveals a sharp increase in the fraction of visually classified strong bars with mass, hinting that strong bars may contribute to the observed downturn in the sSFR above Mknee. We test this hypothesis using a simple but physically motivated numerical model for bar formation, finding that strong bars can rapidly quench star formation in the central few kpc of field galaxies. We conclude that strong bars contribute significantly to the red colors observed in the inner parts of massive galaxies, although additional mechanisms are likely required to quench the star formation in the outer regions of massive spiral galaxies. Intriguingly, when we extrapolate our model to higher redshifts, we successfully recover the observed

  20. Bulge-Disk Decompositions and Structural Bimodality of Ursa Major Cluster Spiral Galaxies

    CERN Document Server

    McDonald, Michael; Tully, R Brent

    2008-01-01

    We present bulge and disk (B/D) decompositions of existing K'-band surface brightness profiles for 65 Ursa Major cluster spiral galaxies. This improves upon the disk-only fits of Tully et al. (1996). The 1996 disk fits were used by Tully & Verheijen (1997) for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new 1D B/D decompositions yield disk structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of 1D surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best fitting Sersic bulge and exponential disk while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disk truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disk central surface brightnesses is bimodal with an F...

  1. Bulge-disc decompositions and structural bimodality of Ursa Major cluster spiral galaxies

    Science.gov (United States)

    McDonald, Michael; Courteau, Stéphane; Tully, R. Brent

    2009-02-01

    We present bulge and disc (B/D) decompositions of existing K' surface brightness profiles for 65 Ursa Major (UMa) cluster spiral galaxies. This improves upon the disc-only fits of Tully et al. The 1996 disc fits were used by Tully & Verheijen for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new one-dimensional B/D decompositions yield disc structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of one-dimensional surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best-fitting Sérsic bulge and the exponential disc while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disc truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disc central surface brightnesses is bimodal with an F-test confidence of 80 per cent. There is also strong evidence for a local minimum in the luminosity function at . A connection between the brightness bimodality and a dynamical bimodality, based on new HI linewidths, is identified. The B/D parameters are presented in Table 1.

  2. Bulge and Clump Evolution in Hubble Ultra Deep Field Clump Clusters, Chains and Spiral Galaxies

    CERN Document Server

    Elmegreen, Bruce G; Fernandez, Maria Ximena; Lemonias, Jenna Jo

    2008-01-01

    Clump clusters and chain galaxies in the Hubble Ultra Deep Field are examined for bulges in the NICMOS images. Approximately 50% of the clump clusters and 30% of the chains have relatively red and massive clumps that could be young bulges. Magnitudes and colors are determined for these bulge-like objects and for the bulges in spiral galaxies, and for all of the prominent star-formation clumps in these three galaxy types. The colors are fitted to population evolution models to determine the bulge and clump masses, ages, star-formation rate decay times, and extinctions. The results indicate that bulge-like objects in clump cluster and chain galaxies have similar ages and 2 to 5 times larger masses compared to the star-formation clumps, while the bulges in spirals have ~6 times larger ages and 20 to 30 times larger masses than the clumps. All systems appear to have an underlying red disk population. The masses of star-forming clumps are typically in a range from 10^7 to 10^8 Msun; their ages have a wide range ar...

  3. Spin alignments of spiral galaxies within the large-scale structure from SDSS DR7

    CERN Document Server

    Zhang, Youcai; Wang, Huiyuan; Wang, Lei; Luo, Wentao; Mo, H J; Bosch, Frank C van den

    2014-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) and Galaxy Zoo 2 (GZ2), we investigate the alignment of spin axes of spiral galaxies with their surrounding large scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes of only have weak tendency to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a \\cluster environment where all the three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  4. Unveiling the sources of disk heating in spiral galaxies with the CALIFA survey

    Science.gov (United States)

    Pinna, F.; Falcón-Barroso, J.; Martig, M.; van de Ven, G.; Lyubenova, M.; Leaman, R.

    2016-06-01

    The stellar velocity ellipsoid (SVE) quantifies the amount of velocity dispersion in the vertical, radial and azimuthal directions. Since different disk heating mechanisms (e.g. spiral arms, giant molecular clouds, mergers, etc) affect these components differently, the SVE can constrain the sources of heating in disk galaxies. At present the 3D nature of the SVE can only be directly measured in the Milky Way but, thanks to integral-field surveys like CALIFA, we are now in position to carry out the same kind of analysis in external galaxies. For this purpose, we have gathered a sample of ~30 intermediate inclined spiral galaxies along the Hubble sequence (S0 to Scd types) with high quality stellar kinematic maps. This allows us to probe the SVE for each galaxy from different line-of-sights in different regions, and thus provide strong constraints on its shape. In this presentation we relate our preliminary findings to realistic numerical simulations of disks with different formation histories (quiescent vs mergers), and to results of previous works.

  5. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    International Nuclear Information System (INIS)

    We examine 8 μm IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (lnR,θ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  6. A new method to estimate local pitch angles in spiral galaxies: Application to spiral arms and feathers in M81 and M51

    Energy Technology Data Exchange (ETDEWEB)

    Puerari, Ivânio [Instituto Nacional de Astrofísica, Optica y Electrónica, Calle Luis Enrique Erro 1, 72840 Santa María Tonantzintla, Puebla (Mexico); Elmegreen, Bruce G. [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Block, David L., E-mail: puerari@inaoep.mx [School of Computational and Applied Mathematics, University of Witwatersrand, Private Bag 3, WITS 2050 (South Africa)

    2014-12-01

    We examine 8 μm IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (lnR,θ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  7. A New Method to Estimate Local Pitch Angles in Spiral Galaxies: Application to Spiral Arms and Feathers in M81 and M51

    Science.gov (United States)

    Puerari, Ivânio; Elmegreen, Bruce G.; Block, David L.

    2014-12-01

    We examine 8 μ m IRAC images of the grand design two-arm spiral galaxies M81 and M51 using a new method whereby pitch angles are locally determined as a function of scale and position, in contrast to traditional Fourier transform spectral analyses which fit to average pitch angles for whole galaxies. The new analysis is based on a correlation between pieces of a galaxy in circular windows of (ln R,θ ) space and logarithmic spirals with various pitch angles. The diameter of the windows is varied to study different scales. The result is a best-fit pitch angle to the spiral structure as a function of position and scale, or a distribution function of pitch angles as a function of scale for a given galactic region or area. We apply the method to determine the distribution of pitch angles in the arm and interarm regions of these two galaxies. In the arms, the method reproduces the known pitch angles for the main spirals on a large scale, but also shows higher pitch angles on smaller scales resulting from dust feathers. For the interarms, there is a broad distribution of pitch angles representing the continuation and evolution of the spiral arm feathers as the flow moves into the interarm regions. Our method shows a multiplicity of spiral structures on different scales, as expected from gas flow processes in a gravitating, turbulent and shearing interstellar medium. We also present results for M81 using classical 1D and 2D Fourier transforms, together with a new correlation method, which shows good agreement with conventional 2D Fourier transforms.

  8. Determining the type of orbits in the central regions of barred galaxies

    Science.gov (United States)

    Zotos, Euaggelos E.; Caranicolas, Nicolaos D.

    2016-02-01

    We use a simple dynamical model which consists of a harmonic oscillator and a spherical component, in order to investigate the regular or chaotic character of orbits in a barred galaxy with a central spherically symmetric nucleus. Our aim is to explore how the basic parameters of the galactic system influence the nature of orbits, by computing in each case the percentage of chaotic orbits, as well as the percentages of different types of regular orbits. We also give emphasis to the types of regular orbits that support either the formation of nuclear rings or the barred structure of the galaxy. We provide evidence that the traditional x1 orbital family does not always dominate in barred galaxy models since we found several other types of resonant orbits which can also support the barred structure. We also found that sparse enough nuclei, fast rotating bars and high energy models can support the galactic bars. On the other hand, weak bars, dense central nuclei, slowly rotating bars and low energy models favor the formation of nuclear rings. We also compare our results with previous related work.

  9. Determining the type of orbits in the central regions of barred galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2016-01-01

    We use a simple dynamical model which consists of a harmonic oscillator and a spherical component, in order to investigate the regular or chaotic character of orbits in a barred galaxy with a central spherically symmetric nucleus. Our aim is to explore how the basic parameters of the galactic system influence the nature of orbits, by computing in each case the percentage of chaotic orbits, as well as the percentages of different types of regular orbits. We also give emphasis to the types of regular orbits that support either the formation of nuclear rings or the barred structure of the galaxy. We provide evidence that the traditional x1 orbital family does not always dominate in barred galaxy models since we found several other types of resonant orbits which can also support the barred structure. We also found that sparse enough nuclei, fast rotating bars and high energy models can support the galactic bars. On the other hand, weak bars, dense central nuclei, slowly rotating bars and low energy models favor t...

  10. Gravitational effects of the faraway matter on the rotation curves of spiral galaxies

    CERN Document Server

    Carati, A

    2011-01-01

    It was recently shown that in cosmology the gravitational action of faraway matter has quite relevant effects, if retardation of the forces and discreteness of matter (with its spatial correlation) are taken into account. Indeed, far matter was found to exert, on a test particle, a force per unit mass of the order of 0.2 cH0 . It is shown here that such a force can account for the observed rotational velocity curves in spiral galaxies, if the force is assumed to be decorrelated beyond a sufficiently large distance, of the order of 1 kpc. In particular we fit the rotation curves of the galaxies NGC 3198, NGC 2403, UGC 2885 and NGC 4725 without any need of introducing dark matter at all. Two cases of galaxies presenting faster than keplerian decay are also considered.

  11. Ram pressure stripping of the multiphase ISM in the Virgo cluster spiral galaxy NGC 4438

    CERN Document Server

    Vollmer, B; Chung, A; Chemin, L; Braine, J; Boselli, A; Beck, R

    2009-01-01

    Ram pressure stripping of the multiphase ISM is studied in the perturbed Virgo cluster spiral galaxy NGC 4438. This galaxy underwent a tidal interaction ~100 Myr ago and is now strongly affected by ram pressure stripping. Deep VLA radio continuum observations at 6 and 20 cm are presented. We detect prominent extraplanar emission to the west of the galactic center, which extends twice as far as the other tracers of extraplanar material. The spectral index of the extraplanar emission does not steepen with increasing distance from the galaxy. This implies in situ re-acceleration of relativistic electrons. The comparison with multiwavelength observations shows that the magnetic field and the warm ionized interstellar medium traced by Halpha emission are closely linked. The kinematics of the northern extraplanar Halpha emission, which is ascribed to star formation, follow those of the extraplanar CO emission. In the western and southern extraplanar regions, the Halpha measured velocities are greater than those of ...

  12. Black Holes in Elliptical and Spiral Galaxies and in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2005-10-01

    Full Text Available Supermassive black holes have been discovered at the centers of galaxies, and also in globular clusters. The data shows correlations between the black hole mass and the elliptical galaxy mass or globular cluster mass. It is shown that this correlation is accurately predicted by a theory of gravity which includes the new dynamics of self-interacting space. In spiral galaxies this dynamics is shown to explain the so-called “dark matter” rotation-curve anomaly, and also explains the Earth based bore-hole g anomaly data. Together these effects imply that the strength of the self-interaction dynamics is determined by the fine structure constant. This has major implications for fundamental physics and cosmology.

  13. Aperture Synthesis CO(J=1-0) Observations and Near-Infrared Photometry of the Non-Barred Seyfert Galaxy NGC 5033

    CERN Document Server

    Kohno, K; Sakamoto, S; Kawabe, R; Ishizuki, S; Matsushita, S

    2003-01-01

    Aperture synthesis observations of CO(J=1-0) emission and near-infrared broad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc) were performed. Our 3".9 x 3".6 resolution CO observations reveal a perturbed distribution and the kinematics of molecular gas in the center of NGC 5033; we find the characteristic gaseous features that are widely observed in barred spiral galaxies, such as two bright CO peaks near the center (separated by ~ 3'' or 270 pc from the nucleus), two offset ridges of CO emission emanating from the CO peaks, and a CO ring (with a radius of ~ 14'' or 1.3 kpc). Double-peaked velocity profiles are also evident near the two CO peaks, implying that these CO peaks are orbit crowding zones in a barred/oval potential. Although NIR data only give an upper limit of the possible bar lengths, due to a large inclination of the NGC 5033 disk (i = 68 deg), our CO data clearly suggests the presence of a small (the semi-major axis of about 12'' - 15'' or 1.1 - 1.4 kpc) nuclear bar (or...

  14. The JCMT Nearby Galaxies Legacy Survey IV. Velocity Dispersions in the Molecular Interstellar Medium in Spiral Galaxies

    CERN Document Server

    Wilson, C D; Irwin, J; Knapen, J H; Israel, F P; Serjeant, S; Attewell, D; Bendo, G J; Brinks, E; Butner, H M; Clements, D L; Leech, J; Matthews, H E; Muehle, S; Mortier, A M J; Parkin, T J; Petitpas, G; Tan, B K; Tilanus, R P J; Usero, A; Vaccari, M; van der Werf, P; Wiegert, T; Zhu, M

    2010-01-01

    An analysis of large-area CO J=3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2-0.4 r(25). Correcting for the average contribution due to the internal velocitydispersions of a population of giant molecular clouds, the average cloud-cloud velocity dispersion across the galactic disks is 6.1 +/- 1.0 km/s (standard deviation 2.9 km/s), in reasonable agreement with previous measurements for the Galaxy andM33. The cloud-cloud velocity dispersion derived from the CO data is on average two times smaller than the HI velocity dispersion measured in the same galaxies. The low cloud-cloudvelocity dispersion implies that the molecular gas is the critical component determining the stability of the galactic disk against...

  15. Star formation histories across the interacting galaxy NGC 6872, the largest-known spiral

    International Nuclear Information System (INIS)

    NGC 6872, hereafter the Condor, is a large spiral galaxy that is interacting with its closest companion, the S0 galaxy IC 4970. The extent of the Condor provides an opportunity for detailed investigation of the impact of the interaction on the current star formation rate and its history across the galaxy, on the age and spatial distribution of its stellar population, and on the mechanism that drives the star formation activity. To address these issues we analyzed the far-ultraviolet (FUV) to near-infrared (near-IR) spectral energy distribution of seventeen 10 kpc diameter regions across the galaxy, and derived their star formation history, current star formation rate, and stellar population and mass. We find that most of the star formation takes place in the extended arms, with very little star formation in the central 5 kpc of the galaxy, in contrast to what was predicted from previous numerical simulations. There is a trend of increasing star formation activity with distance from the nucleus of the galaxy, and no evidence for a recent increase in the current star formation rate due to the interaction. The nucleus itself shows no significant current star formation activity. The extent of the Condor also provides an opportunity to test the applicability of a single standard prescription for conversion of the FUV + IR (22 μm) intensities to a star formation rate for all regions. We find that the conversion factor differs from region to region, arising from regional differences in the stellar populations.

  16. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    CERN Document Server

    Lee, Myung Gyoon

    2016-01-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in Coma. Also we find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3x10^5 M_odot. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions (LF) of the blue (metal-poor) GCs (0.70<(V-I)<1.05) in the halo are estimated to be V(max) =27.11+-0.09 mag and I(max)=26.21+-0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max)=26.25+-0.03 mag. Adopting M_I (max) = -8.56+-0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies, 91+-4 Mpc. Combining this and the Coma radial velocity, we derive a value of the Hubble constant, ...

  17. ASSOCIATIONS OF HIGH-REDSHIFT QUASI-STELLAR OBJECTS WITH ACTIVE, LOW-REDSHIFT SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Following the discovery in the 1960s of radio and optical QSOs it was found that some of them lie very close to low-redshift (z ≤ 0.01) spiral galaxies with separations of ∼<2 arcmin. These were discovered both serendipitously by many observers, and systematically by Arp. They are some of the brightest QSOs in radio and optical wavelengths and are very rare. We have carried out a new statistical analysis of most of those galaxy-QSO pairs and find that the configurations have high statistical significance. We show that gravitational microlensing due to stars or other dark objects in the halos of the galaxies apparently cannot account for the excess. Sampling or identification bias likewise seems unable to explain it. Following this up we selected all ∼4000 QSOs with g ≤ 18 from a catalog of confirmed QSOs in the Sloan Digital Sky Survey, and compared them with various subsets of galaxies from the RC 3 galaxy catalog. In contrast to the earlier results, no significant excess of such QSOs was found around these galaxies. Possible reasons for the discrepancy are discussed.

  18. The Red Spiral Galaxy UGC11680: Clues for the Inside-Out Quenching.

    Science.gov (United States)

    Bárcenas, J.; Sanchez, S. F.

    2016-06-01

    Broadly, galaxies can be divided in two groups, thanks to the Color-Magnitude Diagram: the lively star formation ones, ``The blue Cloud'' and galaxies which halted their star formation, ``The Red Sequence''. It is a currently accepted that the galaxies start their lifespan as a blue objects, turning red when they stop to assembly more mass and thus more stars. Nevertheless, This change need to be quick (˜ 1 Gyr), due to the dearth of galaxies between this two populations (the so called ``green valley'').Previous works have found two distinct stellar mass assembly modes, they are termed as ``the inside-out'' and ``the outside-in'' growth scenarios in the literature. In the ``inside-out'' scenario, mass assembly is finished in the galactic central region. In some cases, the inflow gas can fuel the central SuperMassive BlackHole. The subsequent AGN feedback will then shut-off the central star formation. One possible case of this scenario is the galaxy UGC11680, an unusual face-on red spiral galaxy with an AGN type 2, at the red sequence belonging to the CALIFA survey. We used the so called fossil method to study its star formation history and try to understand what happened to its stellar populations.

  19. Dust Temperatures in the Infrared Space Observatory Atlas of Bright Spiral Galaxies

    CERN Document Server

    Bendo, G J; Wells, M; Gallais, P; Haas, M; Heras, A M; Klaas, U; Laureijs, R J; Leech, K; Lemke, D; Metcalfe, L; Rowan-Robinson, M; Schulz, B; Telesco, C M; Bendo, George J.; Joseph, Robert D.; Wells, Martyn; Gallais, Pascal; Haas, Martin; Heras, Ana M.; Klaas, Ulrich; Laureijs, Rene J.; Leech, Kieron; Lemke, Dietrich; Metcalfe, Leo; Rowan-Robinson, Michael; Schulz, Bernhard; Telesco, Charles

    2003-01-01

    We examine far-infrared and submillimeter spectral energy distributions for galaxies in the Infrared Space Observatory Atlas of Bright Spiral Galaxies. For the 71 galaxies where we had complete 60-180 micron data, we fit blackbodies with lambda^-1 emissivities and average temperatures of 31 K or lambda^-2 emissivities and average temperatures of 22 K. Except for high temperatures determined in some early-type galaxies, the temperatures show no dependence on any galaxy characteristic. For the 60-850 micron range in eight galaxies, we fit blackbodies with lambda^-1, lambda-2, and lambda^-beta (with beta variable) emissivities to the data. The best results were with the lambda^-beta emissivities, where the temperatures were ~30 K and the emissivity coefficient beta ranged from 0.9 to 1.9. These results produced gas to dust ratios that ranged from 150 to 580, which were consistent with the ratio for the Milky Way and which exhibited relatively little dispersion compared to fits with fixed emissivities.

  20. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    CERN Document Server

    Pour-Imani, Hamed; Kennefick, Julia; Davis, Benjamin L; Shields, Douglas W; Abdeen, Mohamed Shameer

    2016-01-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy's image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 {\\mu}m) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 {\\mu}m images have smaller pitch angles than the infrared 8.0 {\\mu}m image...

  1. Does the far-infrared/radio correlation in spiral galaxies extend to the spatial domain

    International Nuclear Information System (INIS)

    A comparison is made between the spatial distribution of the thermal far-infrared and non-thermal radio emission of nearby spiral galaxies. It is now widely believed that the infrared emission detected in the longer wavelength IRAS wavebands (less than 50 microns) arises from at least two distinct sources, e.g., Cox et al., 1986, Persson and Helou, 1987: (1) a warm (T approx. 40 K) component associated with dense dust clouds heated by embedded O and B type stars; and (2) a cooler (T approx. 20 K) component associated with diffuse dust distributed throughout the interstellar matter (ISM) heated by the interstellar radiation field. A link between the warm component and the radio via electrons originating in Type II supernovae (the ultimate fate of many of the O and B type stars responsible for the warm component) has been suggested by numerous authors. The supporting evidence is scarce and inconclusive. Researchers have attempted to provide some insight into the problem by looking at the spatial distribution of the different components in some nearby spiral galaxies, starting with the face-on spiral M51. The source of the far-infrared data is the IRAS chopped photometric channel (CPC) instrument. Warm and cold far-infrared fluxes integrated over all wavelengths and the radio intensity at two frequencies are plotted against radius

  2. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    Science.gov (United States)

    Pour-Imani, Hamed; Kennefick, Daniel; Kennefick, Julia; Davis, Benjamin L.; Shields, Douglas W.; Shameer Abdeen, Mohamed

    2016-08-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy’s image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 μm) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 μm images have smaller pitch angles than the infrared 8.0 μm image in all cases, in agreement with the prediction of density-wave theory. We also used images in the ultraviolet from Galaxy Evolution Explorer, whose pitch angles agreed with the measurements made at 8 μm.

  3. Spiral eigenmodes triggered by grooves in the phase space of disc galaxies

    CERN Document Server

    De Rijcke, Sven

    2015-01-01

    We use linear perturbation theory to investigate how a groove in the phase space of a disc galaxy changes the stellar disc's stability properties. Such a groove is a narrow trough around a fixed angular momentum from which most stars have been removed, rendering part of the disc unresponsive to spiral waves. We find that a groove can dramatically alter a disc's eigenmode spectrum by giving rise to a set of vigorously growing eigenmodes. These eigenmodes are particular to the grooved disc and are absent from the original ungrooved disc's mode spectrum. We discuss the properties and possible origin of the different families of new modes. By the very nature of our technique, we prove that a narrow phase-space groove can be a source of rapidly growing spiral patterns that are true eigenmodes of the grooved disc and that no non-linear processes need to be invoked to explain their presence in N-body simulations of disc galaxies. Our results lend support to the idea that spiral structure can be a recurrent phenomeno...

  4. Is Dark Matter in Spiral Galaxies Cold Gas? I. Observational Constraints and Dynamical Clues About Galaxy Evolution

    OpenAIRE

    Pfenniger, D.; Combes, F; Martinet, L

    1993-01-01

    Based on dynamical constraints about the Hubble sequence evolution, observational data and a number of "conspiracies", we propose that the dark matter around spiral galaxies is in the form of cold gas, essentially in molecular form and rotationally supported. (full A&A paper (in press) available by anonymous ftp at obssd8.unige.ch in /pub/fractal as postscript file: dm_paper_I.ps (170k), or papers I & II + figures as a compressed tar file dm_papers.Z.tar (2.1 Mb)).

  5. The NIR structure of the barred galaxy NGC253 from VISTA

    CERN Document Server

    Iodice, E; Rejkuba, M; Neeser, M J; Greggio, L; Gonzalez, O A; Irwin, M; Emerson, J P

    2014-01-01

    [abridged] We used J and Ks band images acquired with the VISTA telescope as part of the science verification to quantify the structures in the stellar disk of the barred Sc galaxy NGC253. Moving outward from the galaxy center, we find a nuclear ring within the bright 1 kpc diameter nucleus, then a bar, a ring with 2.9 kpc radius. From the Ks image we obtain a new measure of the deprojected length of the bar of 2.5 kpc. The bar's strength, as derived from the curvature of the dust lanes in the J-Ks image, is typical of weak bars. From the deprojected length of the bar, we establish the corotation radius (R_CR=3 kpc) and bar pattern speed (Omega_b = 61.3 km /s kpc), which provides the connection between the high-frequency structures in the disk and the orbital resonances induced by the bar. The nuclear ring is located at the inner Lindblad resonance. The second ring does not have a resonant origin, but it could be a merger remnant or a transient structure formed during an intermediate stage of the bar formatio...

  6. Simulating a slow bar in the low surface brightness galaxy UGC 628

    CERN Document Server

    Chequers, Matthew H; Widrow, Lawrence M; Gilhuly, Colleen

    2016-01-01

    We present a disc-halo N-body model of the low surface brightness galaxy UGC 628, one of the few systems that harbours a "slow" bar with a ratio of corotation radius to bar length of $\\mathcal{R} \\equiv R_c/a_b \\sim 2$. We select our initial conditions using SDSS DR10 photometry, a physically motivated radially variable mass-to-light ratio profile, and rotation curve data from the literature. A global bar instability grows in our submaximal disc model, and the disc morphology and dynamics agree broadly with the photometry and kinematics of UGC 628 at times between peak bar strength and the onset of buckling. Prior to bar formation, the disc and halo contribute roughly equally to the potential in the galaxy's inner region, giving the disc enough self gravity for bar modes to grow. After bar formation there is significant mass redistribution, creating a baryon dominated inner and dark matter dominated outer disc. This implies that, unlike most other low surface brightness galaxies, UGC 628 is not dark matter do...

  7. INTEGRAL FIELD SPECTROSCOPY AND MULTI-WAVELENGTH IMAGING OF THE NEARBY SPIRAL GALAXY NGC 5668 : AN UNUSUAL FLATTENING IN METALLICITY GRADIENT

    Energy Technology Data Exchange (ETDEWEB)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Perez-Gonzalez, P. G.; Gallego, J.; Zamorano, J. [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofisica y CC. de la Atmosfera, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Munoz-Mateos, J. C. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Sanchez, S. F. [Centro Astronomico Hispano Aleman, Calar Alto (CSIC-MPG), C/Jesus Durban Remon 2-2, E-04004 Almeria (Spain); Alonso-Herrero, A. [Instituto de Fisica de Cantabria, CSIC-UC, Avenida de los Castros s/n, 39005 Santander (Spain); Boissier, S., E-mail: ramarino@fis.ucm.es [Laboratoire dAstrophysique de Marseille, OAMP, Universite Aix-Marseille and CNRS UMR 6110, 38 rue Frederic Joliot-Curie, 13388 Marseille cedex 13 (France)

    2012-07-20

    We present an analysis of the full bidimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the Pmas fiber PAcK Integral Field Unit (IFU) at the Calar Alto observatory 3.5 m telescope. We make use of broadband imaging to provide further constraints on the evolutionary history of the galaxy. This data set will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that while inward of r {approx}36'' {approx} 4.4 kpc {approx} 0.36 (D{sub 25}/2) the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r {approx} 36'' flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and circular velocity of {lambda} = 0.053 and v{sub c} = 167 km s{sup -1}, respectively. The metallicity gradient and rotation curve predicted by this best-fitting galaxy model nicely match the values derived from the IFU observations, especially within r {approx}36''. The same is true for the colors despite some small offsets and a reddening in the bluest colors beyond that radius. On the other hand, deviations of some of these properties in the outer disk indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC 5668.

  8. Formation and evolution of bars in disc galaxies

    CERN Document Server

    Athanassoula, E

    2002-01-01

    I follow a bar from its formation, via its evolution, to its destruction and, perhaps, regeneration. I discuss the main features at each stage and particularly the role of the halo. Bars can form even in sub-maximum discs. In fact, such bars can be stronger than bars which have grown in maximum discs. This is due to the response of the halo and, in particular, to the exchange of energy and angular momentum between the disc particles constituting the bar and the halo particles at resonance with it. The bar slowdown depends on the initial central concentration of the halo and the initial value of the disc Q. Contrary to the halo mass distribution, the disc changes its radial density profile considerably during the evolution. Applying the Sackett criterion, I thus find that discs become maximum in many simulations in which they have started off as sub-maximum. I briefly discuss the evolution if a gaseous component is present, as well as the destruction and regeneration of bars.

  9. CATALOG OF OBSERVED TANGENTS TO THE SPIRAL ARMS IN THE MILKY WAY GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Vallée, Jacques P., E-mail: jacques.vallee@nrc-cnrc.gc.ca [Herzberg Astrophysics, National Research Council Canada, National Science Infrastructure portfolio, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada)

    2014-11-01

    From the Sun's location in the Galactic disk, one can use different arm tracers (CO, H I, thermal or ionized or relativistic electrons, masers, cold and hot dust, etc.) to locate a tangent to each spiral arm in the disk of the Milky Way. We present a master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean value is taken—see the Appendix for CO, H II, and masers. The catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3 kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous statistical analysis of the angular offset and linear separation from the mid-arm for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all four spiral arms, one could determine if arm tracers have separate and parallel lanes in the Milky Way. This statistical analysis allows a cross-cut of a Galactic spiral arm to be made, confirming a recent discovery of a linear separation between arm tracers. Here, from the mid-arm's CO to the inner edge's hot dust, the arm halfwidth is about 340 pc; doubling would yield a full arm width of 680 pc. We briefly compare these observations with the predictions of many spiral arm theories, notably the density wave theory.

  10. CATALOG OF OBSERVED TANGENTS TO THE SPIRAL ARMS IN THE MILKY WAY GALAXY

    International Nuclear Information System (INIS)

    From the Sun's location in the Galactic disk, one can use different arm tracers (CO, H I, thermal or ionized or relativistic electrons, masers, cold and hot dust, etc.) to locate a tangent to each spiral arm in the disk of the Milky Way. We present a master catalog of the astronomically observed tangents to the Galaxy's spiral arms, using different arm tracers from the literature. Some arm tracers can have slightly divergent results from several papers, so a mean value is taken—see the Appendix for CO, H II, and masers. The catalog of means currently consists of 63 mean tracer entries, spread over many arms (Carina, Crux-Centaurus, Norma, Perseus origin, near 3 kpc, Scutum, Sagittarius), stemming from 107 original arm tracer entries. Additionally, we updated and revised a previous statistical analysis of the angular offset and linear separation from the mid-arm for each different mean arm tracer. Given enough arm tracers, and summing and averaging over all four spiral arms, one could determine if arm tracers have separate and parallel lanes in the Milky Way. This statistical analysis allows a cross-cut of a Galactic spiral arm to be made, confirming a recent discovery of a linear separation between arm tracers. Here, from the mid-arm's CO to the inner edge's hot dust, the arm halfwidth is about 340 pc; doubling would yield a full arm width of 680 pc. We briefly compare these observations with the predictions of many spiral arm theories, notably the density wave theory

  11. Spatial distribution of far infrared emission in spiral galaxies I. Relation with radio continuum emission

    OpenAIRE

    Mayya, Y. D.; Rengarajan, T. N.

    1997-01-01

    We use high resolution IRAS and 20 cm radio continuum (RC) images of a sample of 22 spiral galaxies to study the correlation between the far infra-red (FIR) and RC emissions within the galactic disks. A combination of exponential and gaussian profiles rather than a single exponential profile is found to be a better representation of the observed intensity profiles in the two bands. The gaussian component, which we show is not due to the effects of limited beam-resolution, contains more than 6...

  12. Angular momentum, accretion and radial flows in chemodynamical models of spiral galaxies

    CERN Document Server

    Pezzulli, Gabriele

    2016-01-01

    Gas accretion and radial flows are key ingredients of the chemical evolution of spiral galaxies. They are also tightly linked to each other (accretion drives radial flows, due to angular momentum conservation) and should therefore be modelled simultaneously. We summarise an algorithm that can be used to consistently compute accretion profiles, radial flows and abundance gradients under quite general conditions and we describe illustrative applications to the Milky Way. We find that gas-phase abundance gradients strongly depend on the angular momentum of the accreting material and, in the outer regions, they are significantly affected by the choice of boundary conditions.

  13. Barred Galaxies in the Abell 901/2 Supercluster with STAGES

    CERN Document Server

    Marinova, I; Heiderman, A; Barazza, F D; Gray, M E; Barden, M; Wolf, C; Peng, C Y; Bacon, D; Balogh, M; Bell, E F; Böhm, A; Caldwell, J A R; Haussler, B; Heymans, C; Jahnke, K; Van Kampen, E; Koposov, S; Lane, K; McIntosh, D H; Meisenheimer, K; Rix, H -W; Sánchez, S F; Taylor, A; Wisotzki, L; Zheng, X

    2009-01-01

    We present a study of bar and host disk evolution in a dense cluster environment, based on a sample of ~800 bright (MV <= -18) galaxies in the Abell 901/2 supercluster at z~0.165. We use HST ACS F606W imaging from the STAGES survey, and data from Spitzer, XMM-Newton, and COMBO-17. We identify and characterize bars through ellipse-fitting, and other morphological features through visual classification. (1) We explore three commonly used methods for selecting disk galaxies. We find 625, 485, and 353 disk galaxies, respectively, via visual classification, a single component S'ersic cut (n <= 2.5), and a blue-cloud cut. In cluster environments, the latter two methods miss 31% and 51%, respectively, of visually-identified disks. (2) For moderately inclined disks, the three methods of disk selection yield a similar global optical bar fraction (f_bar-opt) of 34% +10%/-3%, 31% +10%/-3%, and 30% +10%/-3%, respectively. (3) f_bar-opt rises in brighter galaxies and those which appear to have no significant bulge c...

  14. BARRED GALAXIES IN THE ABELL 901/2 SUPERCLUSTER WITH STAGES

    International Nuclear Information System (INIS)

    We present a study of bar and host disk evolution in a dense cluster environment, based on a sample of ∼800 bright (M V ≤ -18) galaxies in the Abell 901/2 supercluster at z∼ 0.165. We use Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) F606W imaging from the STAGES survey, and data from Spitzer, XMM-Newton, and COMBO-17. We identify and characterize bars through ellipse-fitting, and other morphological features through visual classification. We find the following results. (1) To define the optical fraction of barred disk galaxies, we explore three commonly used methods for selecting disk galaxies. We find 625, 485, and 353 disk galaxies, respectively, via visual classification, a single component Sersic cut (n ≤ 2.5), and a blue-cloud cut. In cluster environments, the latter two methods suffer from serious limitations, and miss 31% and 51%, respectively, of visually identified disks, particularly the many red, bulge-dominated disk galaxies in clusters. (2) For moderately inclined disks, the three methods of disk selection, however, yield a similar global optical bar fraction (fbar-opt) of 34%+10%-3% (115/340), 31%+10%-3% (58/189), and 30%+10%-3% (72/241), respectively. (3) We explore fbar-opt as a function of host galaxy properties and find that it rises in brighter galaxies and those which appear to have no significant bulge component. Within a given absolute magnitude bin, fbar-opt is higher in visually selected disk galaxies that have no bulge as opposed to those with bulges. Conversely, for a given visual morphological class, fbar-opt rises at higher luminosities. Both results are similar to trends found in the field. (4) For bright early-types, as well as faint late-type systems with no evident bulge, the optical bar fraction in the Abell 901/2 clusters is comparable within a factor of 1.1-1.4 to that of field galaxies at lower redshifts (z 10) ∼ 1.7-2.3), the optical bar fraction does not appear to depend strongly on the local

  15. Nuclear, disk-focused wind and the bipolar structure of the spiral galaxy NGC 3079

    International Nuclear Information System (INIS)

    A high-resolution, radio continuum study of the spiral galaxy NGC 3079 is presented which reveals the presence of a figure eight morphology along the minor axis, centered on the nucleus. The nucleus itself dominates the emission from the galaxy. It has an inverted spectrum and is a possible VLBI source. The morphology is successfully modeled as the interaction between a nuclear wind and interstellar gas in the disk and halo. In this model, the wind plows up interstellar material as it propagates away from the nucleus. The disk focuses the wind along the minor axis, thereby creating the observed features. The restricted volume of space where the wind originates and the high energies associated with the wind point to a compact object such as a black hole or an unusually compact and massive star cluster as the source of the wind. 24 references

  16. Central enhancement of nitrogen-to-oxygen abundance ratio in barred galaxies

    CERN Document Server

    Florido, E; Perez, I; Perez-Montero, E; Coelho, P R T; Gadotti, D A

    2015-01-01

    Bar-induced gas inflows towards the galaxy centres are recognized as a key agent for the secular evolution of galaxies. One immediate consequence is the accumulation of gas in the centre of galaxies where it can form stars and alter the chemical and physical properties. We use a sample of nearby face--on disc galaxies with available SDSS spectra to study whether the properties of the ionised gas in the central parts (radii 10^10 M_sun) or galaxies with total stellar mass above ~ 10^10.8 M_sun. In conclusion, we find observational evidence that the presence of a galactic bar affects the central ionised gas properties of disc galaxies, where the most striking effect is an enhancement in the N/O abundance ratio, which can be qualitatively interpreted as due to a different origin or evolutionary processes for less and more massive bulges, with the gaseous phase of the former having currently a closer relation with bars.

  17. Introducing a new 3D dynamical model for barred galaxies

    CERN Document Server

    Jung, Christof

    2015-01-01

    The regular or chaotic dynamics of an analytical realistic three dimensional model composed of a spherically symmetric central nucleus, a bar and a flat disk is investigated. For describing the properties of the bar we introduce a new simple dynamical model and we explore the influence on the character of orbits of all the involved parameters of it, such as the mass and the scale length of the bar, the major semi-axis and the angular velocity of the bar as well as the energy. Regions of phase space with ordered and chaotic motion are identified in dependence on these parameters and for breaking the rotational symmetry. First we study in detail the dynamics in the invariant plane $z = p_z = 0$ using the Poincar\\'e map as a basic tool and then we study the full 3 dimensional case using the SALI method as principal tool for distinguishing between order and chaos. We also present strong evidence obtained through the numerical simulations that our new bar model can realistically describe the formation and the evol...

  18. THE JAMES CLERK MAXWELL TELESCOPE NEARBY GALAXIES LEGACY SURVEY. I. STAR-FORMING MOLECULAR GAS IN VIRGO CLUSTER SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    We present large-area maps of the CO J = 3-2 emission obtained at the James Clerk Maxwell Telescope for four spiral galaxies in the Virgo Cluster. We combine these data with published CO J = 1-0, 24 μm, and Hα images to measure the CO line ratios, molecular gas masses, and instantaneous gas depletion times. For three galaxies in our sample (NGC 4254, NGC 4321, and NGC 4569), we obtain molecular gas masses of 7 x 108 - 3 x 109 M sun and disk-averaged instantaneous gas depletion times of 1.1-1.7 Gyr. We argue that the CO J = 3-2 line is a better tracer of the dense star-forming molecular gas than the CO J = 1-0 line, as it shows a better correlation with the star formation rate surface density both within and between galaxies. NGC 4254 appears to have a larger star formation efficiency (smaller gas depletion time), perhaps because it is on its first passage through the Virgo Cluster. NGC 4569 shows a large-scale gradient in the gas properties traced by the CO J = 3-2/J = 1-0 line ratio, which suggests that its interaction with the intracluster medium is affecting the dense star-forming portion of the interstellar medium directly. The fourth galaxy in our sample, NGC 4579, has weak CO J = 3-2 emission despite having bright 24 μm emission; however, much of the central luminosity in this galaxy may be due to the presence of a central active galactic nucleus.

  19. The DiskMass Survey. X. Radio synthesis imaging of spiral galaxies

    CERN Document Server

    Martinsson, Thomas P K; Bershady, Matthew A; Westfall, Kyle B; Andersen, David R; Swaters, Rob A

    2016-01-01

    We present results from 21 cm radio synthesis imaging of 28 spiral galaxies from the DiskMass Survey obtained with the VLA, WSRT, and GMRT facilities. We detail the observations and data reduction procedures and present a brief analysis of the radio data. We construct 21 cm continuum images, global HI emission-line profiles, column-density maps, velocity fields, and position-velocity diagrams. From these we determine star formation rates (SFRs), HI line widths, total HI masses, rotation curves, and azimuthally-averaged radial HI column-density profiles. All galaxies have an HI disk that extends beyond the readily observable stellar disk, with an average ratio and scatter of R_{HI}/R_{25}=1.35+/-0.22, and a majority of the galaxies appear to have a warped HI disk. A tight correlation exists between total HI mass and HI diameter, with the largest disks having a slightly lower average column density. Galaxies with relatively large HI disks tend to exhibit an enhanced stellar velocity dispersion at larger radii, ...

  20. Satellite accretion in action: a tidally disrupting dwarf spheroidal around the nearby spiral galaxy NGC 253

    CERN Document Server

    Romanowsky, Aaron J; Martin, Nicolas F; Morales, Gustavo; Jennings, Zachary G; GaBany, R Jay; Brodie, Jean P; Grebel, Eva K; Schedler, Johannes; Sidonio, Michael

    2015-01-01

    We report the discovery of NGC 253-dw2, a dwarf spheroidal (dSph) galaxy candidate undergoing tidal disruption around a nearby spiral galaxy, NGC 253 in the Sculptor group: the first such event identified beyond the Local Group. The dwarf was found using small-aperture amateur telescopes, and followed up with Suprime-Cam on the 8 m Subaru Telescope in order to resolve its brightest stars. Using g- and R_c-band photometry, we detect a red giant branch consistent with an old, metal-poor stellar population at a distance of ~ 3.5 Mpc. From the distribution of likely member stars, we infer a highly elongated shape with a semi-major axis half-light radius of (2 +/- 0.4) kpc. Star counts also yield a luminosity estimate of ~ 2x10^6 L_Sun,V (M_V ~ -10.7). The morphological properties of NGC 253-dw2 mark it as distinct from normal dSphs and imply ongoing disruption at a projected distance of ~ 50 kpc from the main galaxy. Our observations support the hierarchical paradigm wherein massive galaxies continously accrete l...

  1. The nature of the UV halo around the spiral galaxy NGC 3628

    CERN Document Server

    Baes, Maarten

    2016-01-01

    Thanks to deep UV observations with GALEX and Swift, diffuse UV haloes have recently been discovered around galaxies. Based on UV-optical colours, it has been advocated that the UV haloes around spiral galaxies are due to UV radiation emitted from the disc and scattered off dust grains at high latitudes. Detailed UV radiative transfer models that take into account scattering and absorption can explain the morphology of the UV haloes, and they require the presence of an additional thick dust disc next the to traditional thin disc for half of the galaxies in their sample. We test whether such an additional thick dust disc agrees with the observed infrared emission in NGC 3628, an edge-on galaxy with a clear signature of a thick dust disc. We extend the far-ultraviolet radiative transfer models to full-scale panchromatic models. Our model, which contains no fine-tuning, can almost perfectly reproduce the observed spectral energy distribution from UV to mm wavelengths. These results corroborate the interpretation...

  2. 2MTF III. HI 21cm observations of 1194 spiral galaxies with the Green Bank Telescope

    CERN Document Server

    Masters, Karen L; Hong, Tao; Jarrett, T H; Koribalski, Baerbel S; Macri, Lucas; Springob, Christopher M; Staveley-Smith, Lister

    2014-01-01

    We present HI 21cm observations of 1194 galaxies out to a redshift of 10,000 km/s selected as inclined spirals (i>60deg) from the 2MASS Redshift Survey. These observations were carried out at the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope (GBT). This observing program is part of the 2MASS Tully-Fisher (2MTF) survey. This project will combine HI widths from these GBT observations with those from further dedicated observing at the Parkes Telescope, from the ALFALFA survey at Arecibo, and S/N>10 and spectral resolution, v_res < 10km/s published widths from a variety of telescopes. We will use these HI widths along with 2MASS photometry to estimate Tully-Fisher distances to nearby spirals and investigate the peculiar velocity field of the local Universe. In this paper we report on detections of neutral hydrogen in emission in 727 galaxies, and measure good signal-to-noise and symmetric HI global profiles suitable for use in the Tully-Fisher relation in 484.

  3. The 60 micron to 20 centimeter infrared-to-radio ratio within spiral galaxies

    International Nuclear Information System (INIS)

    A detailed comparison is presented of the distribution of 60 micron IR and 20 cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal IR and nonthermal radio emission are found to be spatially coincident on scales of less than about 0.4 kpc in the nearest sample galaxies. The IR-red disk in normal spirals appears to be characterized by a shorter scale length than that of the radio continuum disk, suggesting that the IR-to-radio ratio should decrease as a function of radius. A model that successfully accounts for the observations is introduced which is based on the assumptions of steady-state star formation activity within the disk on kpc scales and a tight coupling between the origins of the dust-heating radiation and the radio-emitting cosmic-ray electrons. The underlying source is described as an exponential disk. The results also suggest that a random walk process cannot by itself describe the temporal evolution of cosmic rays. 34 refs

  4. Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

    CERN Document Server

    Mora, Marcelo D; Kissler-Patig, Markus

    2008-01-01

    CONTEXT: Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. AIMS: Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (19), as well as several young star clusters. In this work we aim to confirm the bona fide globular cluster status for 8 of 19 globular cluster candidates and to derive metallicities, ages, and velocities. METHODS: VLT/FORS2 multislit spectroscopy in combination with the Lick/IDS system was used to derive velocities and to constrain metallicities and [alpha/Fe] element ratio of the globular clusters. RESULTS: We confirm the 8 globular clusters as bona fide globular clusters. Their velocities indicate halo or bulge-like kinematics, with little or no overall rotation. From absorption indices such as H_beta, H_gamma, and H_delta and the combined [MgFe]' index, we found that the globular clusters are metal-poor [Z/H]<...

  5. Planetary Nebulae in Face-On Spiral Galaxies. II. Planetary Nebula Spectroscopy

    CERN Document Server

    Herrmann, Kimberly A

    2009-01-01

    As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15 km/s. Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that to first order, the [O III] and Balmer line ratios of planetary nebulae vary little over the top ~1.5 mag of the planetary nebula luminosity function. The only obvious spectral change occurs with [N II], which increases in strength as one p...

  6. Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

    CERN Document Server

    Bournaud, F; Weiss, A; Renaud, F; Mastropietro, C; Teyssier, R

    2014-01-01

    We model the intensity of emission lines from the CO molecule, based on hydrodynamic simulations of spirals, mergers, and high-redshift galaxies with very high resolutions (3pc and 10^3 Msun) and detailed models for the phase-space structure of the interstellar gas including shock heating, stellar feedback processes and galactic winds. The simulations are analyzed with a Large Velocity Gradient (LVG) model to compute the local emission in various molecular lines in each resolution element, radiation transfer and opacity effects, and the intensity emerging from galaxies, to generate synthetic spectra for various transitions of the CO molecule. This model reproduces the known properties of CO spectra and CO-to-H2 conversion factors in nearby spirals and starbursting major mergers. The high excitation of CO lines in mergers is dominated by an excess of high-density gas, and the high turbulent velocities and compression that create this dense gas excess result in broad linewidths and low CO intensity-to-H2 mass r...

  7. Radial metallicity gradients in spiral galaxies from H II regions and planetary nebulae: probing galactic chemical evolution

    Science.gov (United States)

    Stanghellini, Letizia

    2015-08-01

    Radial metallicity gradients, typically observed in spiral galaxies, are excellent constraints for chemical evolution models. The contemporary studies of the two stellar populations, whose progenitors have formed at different times, yield to the chemical and time constraining of the models. In this context, planetary nebula and HII region analysis proved to be ideal two-epochs test populations. We present an assortment of galaxies whose oxygen abundances have been determined both with weak- and strong-line methods, and whose radial metallicity gradients and their evolution in time have disclosed very interesting correlations with the galaxy characteristics. New results from our Gemini/GMOS observations, and a review of the best literature data, set the stage for a better understanding of spiral galaxy evolution.

  8. Complex central structures suggest complex evolutionary paths for barred S0 galaxies

    CERN Document Server

    Dullo, Bililign T; Knapen, Johan H

    2016-01-01

    We investigate three barred lenticular galaxies (NGC 2681, NGC 3945 and NGC 4371) which were previously reported to have complex central structures but without a detailed structural analysis of these galaxies' high-resolution data. We have therefore performed four- to six-component (pseudo-)bulge/disk/bar/ring/point source) decompositions of the composite (Hubble Space Telescope plus ground-based) surface brightness profiles. We find that NGC 2681 hosts three bars, while NGC 3945 and NGC 4371 are double- and single-barred galaxies, respectively, in agreement with past isophotal analysis. We find that the bulges in these galaxies are compact, and have S\\'ersic indices of $n\\sim 2.2 - 3.6$ and stellar masses of $M_{*}$ $\\sim 0.28\\times10^{10} - 1.1\\times10^{10} M_{\\sun}$. NGC 3945 and NGC 4371 have intermediate-scale `pseudo-bulges' that are well described by a S\\'ersic model with low $n \\la 0.5$ instead of an exponential ($n=1$) profile as done in the past. We measure emission line fluxes enclosed within 9 dif...

  9. Cold dust in the giant barred galaxy NGC 1365

    OpenAIRE

    Tabatabaei, F. S.; Weiß, A.; Combes, F; Henkel, C.; Menten, K. M.; Beck, R.; Kovács, A.; Güsten, R.

    2013-01-01

    Constraining the physcial properties of dust requires observations at submm wavelengths. This will provide important insight into the gas content of galaxies. We mapped NGC 1365 at 870 μm with LABOCA, the Large APEX Bolometer Camera, allowing us to probe the central mass concentration as well as the rate at which the gas flows to the center. We obtained the dust physical properties both globally and locally for different locations in the galaxy. A 20 K modified black body represents about 98%...

  10. Cold dust in giant barred galaxy NGC1365,

    OpenAIRE

    Tabatabaei, F. S.; Weiss, A; Combes, F; Henkel, C.; Menten, K. M.; Beck, R.; Kovacs, A.; Guesten R.: 2013,

    2013-01-01

    Observations of galaxies at sub-millimeter wavelengths, where the emission is mainly due to cold dust, are required to constrain the dust physical properties and provide important insight on the gas content of galaxies. We mapped NGC1365 at 870um with LABOCA, the Large APEX Bolometer Camera, allowing us to probe the central mass concentration as well as the rate at which the gas flows to the center. We obtained the dust physical properties both globally and locally for different locations in ...

  11. STAR FORMATION ON SUBKILOPARSEC SCALE TRIGGERED BY NON-LINEAR PROCESSES IN NEARBY SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Momose, Rieko [Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Koda, Jin; Donovan Meyer, Jennifer [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Kennicutt, Robert C. Jr [Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA (United Kingdom); Egusa, Fumi [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Calzetti, Daniela; Liu Guilin [Astronomy Department, University of Massachusetts, Amherst, MA 01003-9305 (United States); Okumura, Sachiko K.; Sawada, Tsuyoshi [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Scoville, Nick Z. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kuno, Nario, E-mail: momo.s.rieko@nao.ac.jp, E-mail: momo@icrr.u-tokyo.ac.jp [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)

    2013-07-20

    We report a super-linear correlation for the star formation law based on new CO(J = 1-0) data from the CARMA and NOBEYAMA Nearby-galaxies (CANON) CO survey. The sample includes 10 nearby spiral galaxies, in which structures at sub-kpc scales are spatially resolved. Combined with the star formation rate surface density traced by H{alpha} and 24 {mu}m images, CO(J = 1-0) data provide a super-linear slope of N = 1.3. The slope becomes even steeper (N = 1.8) when the diffuse stellar and dust background emission is subtracted from the H{alpha} and 24 {mu}m images. In contrast to the recent results with CO(J = 2-1) that found a constant star formation efficiency (SFE) in many spiral galaxies, these results suggest that the SFE is not independent of environment, but increases with molecular gas surface density. We suggest that the excitation of CO(J = 2-1) is likely enhanced in the regions with higher star formation and does not linearly trace the molecular gas mass. In addition, the diffuse emission contaminates the SFE measurement most in regions where the star formation rate is law. These two effects can flatten the power-law correlation and produce the apparent linear slope. The super-linear slope from the CO(J = 1-0) analysis indicates that star formation is enhanced by non-linear processes in regions of high gas density, e.g., gravitational collapse and cloud-cloud collisions.

  12. Simulations of Barred Galaxies in Triaxial Dark Matter Haloes: The Effects of Gas

    CERN Document Server

    Machado, Rubens E G; Rodionov, S A

    2012-01-01

    The baryonic discs of galaxies are believed to alter the shapes of the dark matter haloes in which they reside. We perform a set of hydrodynamical N-body simulations of disc galaxies with triaxial dark matter haloes, using elliptical discs with a gaseous component as initial conditions. We explore models of different halo triaxiality and also of different initial gas fractions, which allows us to evaluate how each affects the formations of the bar. Due to star formation, models of all halo shapes and of all initial gas fractions reach approximately the same gas content at the end of the simulation. Nevertheless, we find that the presence of gas in the early phases has important effects on the subsequent evolution. Bars are generally weaker for larger initial gas content and for larger halo triaxiality. The presence of gas, however, is a more efficient factor in inhibiting the formation of a strong bar than halo triaxiality is.

  13. Differences between CO- and calcium triplet-derived velocity dispersions in spiral galaxies: evidence for central star formation?

    CERN Document Server

    Riffel, Rogemar A; Mason, Rachel; Rodriguez-Ardila, Alberto; Martins, Lucimara; Riffel, Rogerio; Diaz, Ruben; Colina, Luis; Alonso-Herrero, Almudena; Flohic, Helene; Martin, Omaira Gonzalez; Lira, Paulina; McDermid, Richard; Almeida, Cristina Ramos; Schiavon, Ricardo; Thanjavur, Karun; Dutra, Daniel Ruschel; Winge, Claudia; Perlman, Eric

    2014-01-01

    We examine the stellar velocity dispersions (sigma) of a sample of 48 galaxies, 35 of which are spirals, from the Palomar nearby galaxy survey. It is known that for ultra-luminous infrared galaxies (ULIRGs) and merger remnants thesigma derived from the near-infrared CO band-heads is smaller than that measured from optical lines, while no discrepancy between these measurements is found for early-type galaxies. No such studies are available for spiral galaxies - the subject of this paper. We used cross-dispersed spectroscopic data obtained with the Gemini Near-Infrared Spectrograph (GNIRS), with spectral coverage from 0.85 to 2.5um, to obtain sigma measurements from the 2.29 $\\mu$m CO band-heads (sigma_{CO}), and the 0.85 um calcium triplet (sigma_{CaT}). For the spiral galaxies in the sample, we found that sigma_{CO} is smaller than sigma_{CaT}, with a mean fractional difference of 14.3%. The best fit to the data is given by sigma_{opt} = (46.0+/-18.1) + (0.85+/-0.12)sigma_{CO}. This "sigma discrepancy" may be...

  14. Multi-Wavelength Properties of Barred Galaxies in the Local Universe. I: Virgo Cluster

    CERN Document Server

    Giordano, Lea; Moore, Ben; Saintonge, Amelie

    2010-01-01

    We study in detail how the barred galaxy fraction varies as a function of luminosity, HI gas mass, morphology and color in the Virgo cluster in order to provide a well defined, statistically robust measurement of the bar fraction in the local universe spanning a wide range in luminosity (factor of ~100) and HI gas mass. We combine multiple public data-sets (UKIDSS near-infrared imaging, ALFALFA HI gas masses, GOLDMine photometry). After excluding highly inclined systems, we define three samples where galaxies are selected by their B-band luminosity, H-band luminosity, and HI gas mass. We visually assign bars using the high resolution H-band imaging from UKIDSS. When all morphologies are included, the barred fraction is ~17-24% while for morphologically selected discs, we find that the barred fraction in Virgo is ~29-34%: it does not depend strongly on how the sample is defined and does not show variations with luminosity or HI gas mass. The barred fraction depends most strongly on the morphological compositio...

  15. Galaxy Morphology

    CERN Document Server

    Buta, Ronald J

    2013-01-01

    Galaxy morphology has many structures that are suggestive of various processes or stages of secular evolution. Internal perturbations such as bars can drive secular evolution through gravity torques that move gas into the central regions and build up a flattened, disk-like central bulge, or which may convert an open spiral pseudoring into a more closed ring. Interaction between individual components of a galaxy, such as between a bar and a dark halo, a bar and a central mass concentration, or between a perturbation and the basic state of a stellar disk, can also drive secular transformations. In this series of lectures, I review many aspects of galaxy morphology with a view to delineating some of the possible evolutionary pathways between different galaxy types.

  16. The DiskMass Survey : VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present ionized-gas ([OIII]lambda 5007 angstrom) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (h(R)). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 angs

  17. Spiral structure of the Galaxy: a statistical analysis of the spatial distribution of bright stars and open clusters

    International Nuclear Information System (INIS)

    A statistical analysis of space distribution of bright stars and open clusters in the fourth quadpant of the Galaxy is performed. It is shown that, with a probability equal practically to 100%, the Saggitarius-Carina spiral feature cannot be a chance density fluctuation in an actually homogeneous distribution of stars. The geometrical parameters of this feature are estimated: the pitch angle i=6 deg,6+ and the distance from the Sun R1=1.0 kpc. It is found that there is a statistically significant age gradient across the Saggitarius-Carina spiral arm: the young objects (O, M 1-2 staps) are shifted with Cespect to the older objects (the B, A, F) to the inner edge of the arm approximately by 100 pc. This result favours the density wave nature of the spiral structure of the Galaxy

  18. Spiral structure of the Galaxy: a statistical analysis of the spatial distribution of bright stars and open clusters

    Energy Technology Data Exchange (ETDEWEB)

    Pavlovskaya, E.D.; Suchkov, A.A. (Moskovskij Gosudarstvennyj Univ. (USSR). Gosudarstvennyj Astronomicheskij Inst. ' ' GAISh' ' ; Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR))

    A statistical analysis of space distribution of bright stars and open clusters in the fourth quadrant of the Galaxy is performed. It is shown that, with a probability equal practically to 100%, the Saggitarius-Carina spiral feature cannot be a chance density fluctuation in an actually homogeneous distribution of stars. The geometrical parameters of this feature are estimated: the pitch angle i=6 deg,6+ and the distance from the Sun R/sub 1/=1.0 kpc. It is found that there is a statistically significant age gradient across the Saggitarius-Carina spiral arm: the young objects (O, M 1-2 staps) are shifted with respect to the older objects (the B, A, F) to the inner edge of the arm approximately by 100 pc. This result favours the density wave nature of the spiral structure of the Galaxy.

  19. Spiral-induced velocity and metallicity patterns in a cosmological zoom simulation of a Milky Way-sized galaxy

    CERN Document Server

    Grand, Robert J J; Kawata, Daisuke; Minchev, Ivan; Sánchez-Blázquez, Patricia; Gómez, Facundo A; Marinacci, Federico; Pakmor, Rüdiger; Campbell, David J R

    2016-01-01

    We use a high resolution cosmological zoom simulation of a Milky Way-sized halo to study the observable features in velocity and metallicity space associated with the dynamical influence of spiral arms. For the first time, we demonstrate that spiral arms, that form in a disc in a fully cosmological environment with realistic galaxy formation physics, drive large-scale systematic streaming motions. In particular, on the trailing edge of the spiral arms the peculiar galacto-centric radial and tangential velocity field is directed radially outward and tangentially backward, whereas it is radially inward and tangentially forward on the leading edge. Owing to the negative radial metallicity gradient, this systematic motion drives, at a given radius, an azimuthal variation in the residual metallicity that is characterised by a metal rich trailing edge and a metal poor leading edge. We show that these signatures are theoretically observable in external galaxies with Integral Field Unit instruments such as VLT/MUSE, ...

  20. The AMIGA sample of isolated galaxies: VIII. The rate of asymmetric HI profiles in spiral galaxies

    CERN Document Server

    Espada, D; Huchtmeier, W K; Sulentic, J; Verley, S; Leon, S; Sabater, J

    2011-01-01

    (abridged) Measures of the HI properties of a galaxy are among the most sensitive interaction diagnostic at our disposal. We report here on a study of HI profile asymmetries (e.g., lopsidedness) in a sample of some of the most isolated galaxies in the local Universe. This presents us with an excellent opportunity to quantify the range of intrinsic HI asymmetries and provides us with a zero-point calibration for evaluating these measurements in less isolated samples. We characterize the HI profile asymmetries and search for correlations between HI asymmetry and their environments, as well as their optical and far infrared (FIR) properties. We use high signal-to-noise global HI profiles for galaxies in the AMIGA project (http://amiga.iaa.csic.es). We restrict our study to N=166 galaxies with accurate measures of the HI shape properties. We quantify asymmetries using a flux ratio parameter. The asymmetry parameter distribution of our isolated sample is well described by a Gaussian model. The width of the distrib...

  1. The Extraordinary ``Superthin'' Spiral Galaxy UGC 7321. II. The Vertical Disk Structure

    Science.gov (United States)

    Matthews, L. D.

    2000-10-01

    We explore the vertical light distribution as a function of galactocentric radius in the edge-on (i=88deg) Sd ``superthin'' galaxy UGC 7321. UGC 7321 is a low-luminosity spiral (MB,i=-17.0) with a diffuse, low surface brightness stellar disk and no discernible bulge component. Within ~0.25‧ (~725 pc) of the disk center the global luminosity profile of UGC 7321 can be reasonably characterized by an exponential function with a scale height hz~2.9" (~140 pc) in H and hz~3.1" (~150 pc) in R, making this among the thinnest galaxy disks known. Near the disk center we derive a ratio of disk scale length to global disk scale height hr/hz~14 in both H and R; near the edge of the disk, hr/hz~10. At intermediate galactocentric radii (0.25‧Matthews, Gallagher, & van Driel, suggest that UGC 7321 has multiple disk subcomponents comprised of stellar populations with different ages and velocity dispersions. Thus even examples of the thinnest pure disk galaxies exhibit complex structure and signatures of dynamical heating.

  2. The fluorescence-dominated X-ray spectrum of the spiral galaxy NGC 6552

    Science.gov (United States)

    Fukazawa, Yasushi; Makishima, Kazuo; Ebisawa, Ken; Fabian, Andrew C.; Gendreau, Keith C.; Ikebe, Yasushi; Iwasawa, Kazushi; Kii, Tsuneo; Mushotzky, Richard F.; Ohashi, Takaya

    1994-01-01

    A hard X-ray source with a 2-10 keV flux of approximately 6 x 10(exp -13) ergs/sec/sq cm was detected with ASCA in the north ecliptic pole region. It is identified with the spiral galaxy NGC 6552 at a redshift of z = 0.026, which is optically classified as a Seyfert 2 galaxy. The X-ray spectrum consists of a series of atomic K-emission lines from (nearly-) neutral species of at least seven abundant elements, and a heavily absorbed (N(sub H) approx. = 6 x 10(exp 23)/sq cm) hard continuum. The iron line has an equivalent width as large as approximately 0.9 keV. Our results show that NGC 6552 is an extreme type 2 Seyfert galaxy, in which the fluorescent lines are produced when hard X-rays from a hidden active nucleus are reflected off thick cool matter into our line of sight. The intrinsic 2-10 keV luminosity of the nucleus is estimated to be at least 6 x 10(exp 42) ergs/s.

  3. On the effective oxygen yield in the disks of spiral galaxies

    CERN Document Server

    Zasov, A; Abramova, O

    2015-01-01

    The factors influencing chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce a gas-phase abundance of heavy elements (metallicity) whereas the ongoing star formation continuously increases it. To exclude the stellar nucleosynthesis from consideration, we analyze for the sample of 14 spiral galaxies the radial distribution of the effective yield of oxygen $y_{eff}$, which would be identical to the true stellar yield (per stellar generation) $y_o$ if the evolution followed the closed box model. As the initial data for gas-phase abundance we used the O/H radial profiles from Moustakas, Kennicutt, Tremonti et al. (2010), based on two different calibrations (Pilyugin & Thuan 2005 (PT2005) and Kobulnicky & Kewley 2004 (KK2004) methods). In most of galaxies with the PT2005 calibration, which we consider as a preferred one, the yield $y_{eff}$ in the main disk ($R \\ge 0.2~R_{25}$, where $R_{25}$ is the optical radius) increases with radius, remaining lower than the empi...

  4. The kinematics and spiral structure of the Galaxy from the neutral hydrogen

    Science.gov (United States)

    Petrovskaya, I. V.

    The kinematical and structural characteristics of the Galaxy are investigated using the whole 21-cm line profile of the neutral hydrogen emission. The concerted rotation curve and the spiral arms parameters are obtained. The Galaxy is found to have four armes with the pitch angle i = 14^circ in the region R >= 0.6R_0 and the gaseous ring when 0.4 kpk. The rotation velocity has a signature with the depression approximatedly 20 km/s near R = R_0. The velocity jump may be connected with giant vortices near corotation region. The parameters of the anticyclonic motion in that region are investigated. Our method of interpretation of the 21 cm profile gives the possibility to investigate z-dependance of the velocity field. To solve this problem for the inner region of the Galaxy (R

  5. A supergiant supernova-blown bubble in the spiral galaxy NGC 1620

    CERN Document Server

    Vader, J P; Vader, J Patricia; Chaboyer, Brian

    1994-01-01

    We present UBR and H\\alpha imaging of NGC 1620, a highly inclined spiral galaxy that contains a large scale, arc-like feature of radius 3 kpc in its outer disk at a distance of \\sim 11 kpc from the center. What is unusual about this arc-like feature is its stellar nature and the presence of a luminous star cluster at its center. The arc is fragmented into HII region complexes and OB star clusters and shows two kinks in optical continuum light. It spans an angle of 220^{\\circ} on our U image and a full, though fragmented, circle on an unsharp masked R image. It is centered on a young star cluster that is the most luminous clump in blue optical continuum light besides the nucleus of the galaxy. This central star cluster has UBR colors and a surface brightness similar to those of other HII regions, but is a relatively weak H\\alpha emitter. It consists of at least three unresolved condensations in optical continuum light. Its location at the center of the arc and its prominence within the galaxy suggests that it ...

  6. Extraplanar Emission-Line Gas in Edge-On Spiral Galaxies. II. Optical Spectroscopy

    CERN Document Server

    Miller, S T; Miller, Scott T.; Veilleux, Sylvain

    2003-01-01

    The results from deep long-slit spectroscopy of nine edge-on spiral galaxies with known extraplanar line emission are reported. Emission from Halpha, [N II] lambda 6548, 6583, and [S II] lambda 6716, 6731 is detected out to heights of a few kpc in all of these galaxies. Several other fainter diagnostic lines such as [O I] lambda 6300, [O III] lambda 4959, 5007, and He I lambda 5876 are also detected over a smaller scale. The relative strengths, centroids and widths of the various emission lines provide constraints on the electron density, temperature, reddening, source(s) of ionization, and kinematics of the extraplanar gas. In all but one galaxy, photoionization by massive OB stars alone has difficulties explaining all of the line ratios in the extraplanar gas. Hybrid models that combine photoionization by OB stars and another source of ionization such as photoionization by turbulent mixing layers or shocks provide a better fit to the data. The (upper limits on the) velocity gradients measured in these galax...

  7. Molecular hydrogen beyond the optical edge of an isolated spiral galaxy

    CERN Document Server

    Braine, J; Braine, Jonathan; Herpin, Fabrice

    2004-01-01

    We know little about the outermost portions of galaxies because there is little light coming from them. We do know that in many cases atomic hydrogen (HI) extends well beyond the optical radius \\cite{Casertano91}. In the centers of galaxies, however, molecular hydrogen (H2) usually dominates by a large factor, raising the question of whether H2 is abundant also in the outer regions but hitherto unseen.Here we report the detection of emission from carbon monoxide (CO), the most abundant tracer of H2, beyond the optical radius of the nearby galaxy NGC 4414. The molecular clouds probably formed in the regions of relatively high HI column density and in the absence of spiral density waves. The relative strength of the lines from the two lowest rotational levels indicates that both the temperature and density of the H2 are quite low compared to conditions closer to the center. The inferred surface density of the molecular material continues the monotonic decrease from the inner regions. We conclude that while mole...

  8. The spiral-compact galaxy pair AM 2208-251: Computer simulations versus observations

    Science.gov (United States)

    Klaric, Mario; Byrd, Gene G.

    1990-01-01

    The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral. Bertola, Huchtmeier, and Zeilinger (1990) have presented optical spectroscopic as well as single dish 21 cm observations of this system. Their spectroscopic data show, via emission lines lambda lambda 3727-29A, a rising rotation curve near the nucleus. These spectroscopic observations may indicate a tidal interaction in the system. In order to learn more about such pairs, the authors simulated the interaction using the computer model developed by Miller (1976 a,b, 1978) and modified by the authors (Byrd 1986, 1987, 1988). To do the simulation they need an idea of the mutual orbits of the two galaxies. Their computer model is a two-dimensional polar N-body program. It consists of a self-gravitating disk of particles, within an inert axially symmetric stabilizing halo potential. The particles are distributed in a 24(radial) by 36(azimuthal) polar grid. Self consistent calculations can be done only within the grid area. The disk is modeled with a finite Mestel disk, where all the particles initially move in circular orbits with constant tangential velocities (Mestel 1963), resulting in a flat rotation curve. The gas particles in the spiral's disk, which make up 30 percent of its mass, collide in the following manner. The number of particles in each bin of the polar grid is counted every time step. If it is greater than a given critical density, all the particles in the bin collide, obtaining in the result the same velocities, equal to the average for the bin. This process produces clumps of gas particles-the star formation sites. The authors suppress the collision in the inner part of the disk (within the circle r = 6) to represent the hole seen in the gas in the nuclear bulge of spirals. They thus avoid spurious effects due to collisions in that region. They also varied the size of

  9. The spiral-compact galaxy pair AM 2208-251: Computer simulations versus observations

    Science.gov (United States)

    Klaric, Mario; Byrd, Gene G.

    1990-11-01

    The system AM2208-251 is a roughly edge-on spiral extending east-west with a smaller round compact E system about 60 arcsec east of the spiral nucleus along the major axis of the spiral. Bertola, Huchtmeier, and Zeilinger (1990) have presented optical spectroscopic as well as single dish 21 cm observations of this system. Their spectroscopic data show, via emission lines lambda lambda 3727-29A, a rising rotation curve near the nucleus. These spectroscopic observations may indicate a tidal interaction in the system. In order to learn more about such pairs, the authors simulated the interaction using the computer model developed by Miller (1976 a,b, 1978) and modified by the authors (Byrd 1986, 1987, 1988). To do the simulation they need an idea of the mutual orbits of the two galaxies. Their computer model is a two-dimensional polar N-body program. It consists of a self-gravitating disk of particles, within an inert axially symmetric stabilizing halo potential. The particles are distributed in a 24(radial) by 36(azimuthal) polar grid. Self consistent calculations can be done only within the grid area. The disk is modeled with a finite Mestel disk, where all the particles initially move in circular orbits with constant tangential velocities (Mestel 1963), resulting in a flat rotation curve. The gas particles in the spiral's disk, which make up 30 percent of its mass, collide in the following manner. The number of particles in each bin of the polar grid is counted every time step. If it is greater than a given critical density, all the particles in the bin collide, obtaining in the result the same velocities, equal to the average for the bin. This process produces clumps of gas particles-the star formation sites. The authors suppress the collision in the inner part of the disk (within the circle r = 6) to represent the hole seen in the gas in the nuclear bulge of spirals. They thus avoid spurious effects due to collisions in that region. They also varied the size of

  10. On the Galactic Spiral Arms Nature as revealed by rotation frequencies

    CERN Document Server

    Roca-Fàbrega, Santi; Figueras, Francesca; Romero-Gómez, Mercè; Velázquez, Hector; Antoja, Teresa; Pichardo, Bárbara

    2013-01-01

    High resolution N-body simulations using different codes and initial condition techniques reveal two different behaviours for the rotation frequency of transient spiral arms like structures. Whereas unbarred disks present spiral arms nearly corotatingwith disk particles, strong barred models (bulged or bulge-less) quickly develop a bar-spiral structure dominant in density, with a pattern speed almost constant in radius. As the bar strength decreases the arm departs from bar rigid rotation and behaves similar to the unbarred case. In strong barred models we detect in the frequency space other subdominant and slower modes at large radii, in agreement with previous studies, however we also detect them in the configuration space. We propose that the distinctive behaviour of the dominant spiral modes can be exploited in order to constraint the nature of Galactic spiral arms by the astrometric survey GAIA and by 2-D spectroscopic surveys like CALIFA and MANGA in external galaxies.

  11. Structure of the Galactic Bulge: Is the Milky Way a Double-barred Galaxy?

    Energy Technology Data Exchange (ETDEWEB)

    Nishiyama, Shogo [National Astronomical Observatory of Japan, Mitaka, Tokyo (Japan); Nagata, Tetsuya [Department of Astronomy, Kyoto University, Kyoto (Japan)

    2006-12-15

    Using the data of the IRSF/SIRIUS infrared survey along the Galactic plane ( l {<=} 10.{sup 0}5 at b = +1{sup 0}), we find a distinct structure, which is probably a secondary bar, inside the primary bar of our Galaxy. The apparent magnitude peak of Bulge red clump stars changes continuously from K{sub S} {approx} 13.5 (l = -10{sup 0}) to K{sub S} {approx} 12.3 (l = +10{sup 0}), and this can be explained by the bar structure of the Galactic Bulge. However, the apparent magnitude changes by only {approx} 0.1 mag over the central 8{sup 0}, and this indicates that there is a distinct structure inside the primary bar. In the process of the distance derivation, we have used the infrared extinction law in the J, H, and K{sub S} bands toward the Galactic center newly determined from our survey.

  12. Structure of the Galactic Bulge: Is the Milky Way a Double-barred Galaxy?

    International Nuclear Information System (INIS)

    Using the data of the IRSF/SIRIUS infrared survey along the Galactic plane ( l ≤ 10.05 at b = +10), we find a distinct structure, which is probably a secondary bar, inside the primary bar of our Galaxy. The apparent magnitude peak of Bulge red clump stars changes continuously from KS ∼ 13.5 (l = -100) to KS ∼ 12.3 (l = +100), and this can be explained by the bar structure of the Galactic Bulge. However, the apparent magnitude changes by only ∼ 0.1 mag over the central 80, and this indicates that there is a distinct structure inside the primary bar. In the process of the distance derivation, we have used the infrared extinction law in the J, H, and KS bands toward the Galactic center newly determined from our survey

  13. A Luminous X-Ray Flare from the Nucleus of the Dormant Bulgeless Spiral Galaxy NGC 247

    OpenAIRE

    FENG, HUA; Ho, Luis C.; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-01-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity of up to 2 x 10^(39) erg s^(−1) in the 0.3–10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3–4 keV, no pulsations on timescales longer than 150 ...

  14. Galaxy Secular Mass Flow Rate Determination Using the Potential-Density Phase Shift Approach: Application to Six Nearby Spiral Galaxies

    CERN Document Server

    Zhang, Xiaolei

    2016-01-01

    Using the potential-density phase shift approach developed by the present authors in earlier publications, we estimate the magnitude of radial mass accretion/excretion rates across the disks of six nearby spiral galaxies having a range of Hubble types. Our goal is to examine these rates in the context of bulge building and secular morphological evolution along the Hubble sequence. Stellar surface density maps of the sample galaxies are derived from SINGS 3.6um and SDSS i-band images. Corresponding molecular and atomic gas surface densities are derived from published CO(1-0) and HI interferometric observations of the BIMA SONG, THINGS, and VIVA surveys. The mass flow rate calculations utilize a volume-type torque integral to calculate the angular momentum exchange rate between the basic state disk matter and density wave modes. The potential-density phase shift approach yields angular momentum transport rates several times higher than those estimated using the Lynden-Bell and Kalnajs (1972) approach. The curre...

  15. The Bulgeless Seyfert/LINER Galaxy NGC 3367: Disk, Bar, Lopsidedness and Environment

    CERN Document Server

    Hernández-Toledo, H M; Valenzuela, O; Puerari, I; García-Barreto, J A; Moreno-Díaz, E; Bravo-Alfaro, H

    2011-01-01

    NGC3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and a search for evidence of recent interaction based on new UBVRI Halpha and JHK images and on archival Halpha Fabry-Perot and HI VLA data. From a coupled 1D/2D GALFIT bulge/bar/disk decomposition an (B/D ~ 0.07-0.1) exponential pseudobulge is inferred in all the observed bands. A NIR estimate of the bar strength = 0.44 places NGC 3367 bar among the strongest ones. The asymmetry properties were studied using (1) optical and NIR CAS indexes (2) the stellar (NIR) and gaseous (Halpha, HI) A_1 Fourier mode amplitudes and (3) the HI integrated profile and HI mean intensity distribution. While the average stellar component shows asymmetry values close to the average found in the Local Universe for isolated galaxies, the young stellar component and gas values are largely decoupled showing significantly larger A_1 mod...

  16. GHASP: an H$\\alpha$ kinematic survey of spiral galaxies - X. Surface photometry, decompositions and the Tully-Fisher relation in the Rc-band

    CERN Document Server

    Barbosa, C E; Amram, P; Ferrari, F; Russeil, D; Epinat, B; Perret, V; Adami, C; Marcelin, M

    2015-01-01

    We present Rc-band surface photometry for 170 of the 203 galaxies in GHASP, Gassendi H-Alpha survey of SPirals, a sample of late-type galaxies for which high-resolution Fabry-Perot H{\\alpha} maps have previously been obtained. Our data set is constructed by new Rc-band observations taken at the Observatoire de Haute-Provence (OHP), supplemented with Sloan Digital Sky Survey (SDSS) archival data, obtained with the purpose of deriving homogeneous photometric profiles and parameters. Our results include Rc-band surface brightness profiles for 170 galaxies and $ugriz$ profiles for 108 of these objects. We catalogue several parameters of general interest for further reference, such as total magnitude, effective radius and isophotal parameters -- magnitude, position angle, ellipticity and inclination. We also perform a structural decomposition of the surface brightness profiles using a multi-component method in order to separate disks from bulges and bars, and to observe the main scaling relations involving luminos...

  17. The angular momentum of hot coronae around spiral galaxies and its impact on the evolution of star forming discs

    Science.gov (United States)

    Pezzulli, G.; Fraternali, F.; Binney, J.

    2016-06-01

    Galaxy formation theory and recent observations indicate that spiral galaxies are surrounded by massive and hot coronae, which potentially constitute a huge source of mass and angular momentum for the star forming discs embedded within them. Accretion from these reservoirs is likely a key ingredient for the evolution of spiral galaxies, but our understanding of the involved processes requires more observational and theoretical investigation, both at global and local scales. In this talk, I focus on some theoretical aspects of the angular momentum distribution of hot coronae. I address, in particular, whether these structures can sustain the inside-out growth of spiral galaxies and what are the dynamical consequences of the accretion of hot coronal gas onto the disc. These processes can have a big impact on observable quantities, most notably gas-phase abundance gradients, which can be used to put constraints on theory. I finally mention ongoing work to understand whether a cosmologically motivated angular momentum distribution for the hot gas is compatible with the constraints from galaxy evolution.

  18. Neutrino Flux from Cosmic Ray Accelerators in the Cygnus Spiral Arm of the Galaxy

    CERN Document Server

    Anchordoqui, Luis A; Montaruli, T; O'Murchadha, A; Anchordoqui, Luis; Halzen, Francis; Montaruli, Teresa; Murchadha, Aongus O'

    2006-01-01

    Intriguing evidence has been accumulating for the production of cosmic rays in the Cygnus region of the Galactic plane. We here show that the IceCube experiment can produce incontrovertible evidence for cosmic ray acceleration by observing neutrinos from the decay of charged pions accompanying the TeV photon flux observed in the HEGRA, Whipple, Tibet and Milagro experiments. Our assumption is that the TeV photons observed are the decay products of neutral pions produced by cosmic ray accelerators in the nearby spiral arm of the Galaxy. Because of the proximity of the sources, IceCube will obtain evidence at the 5sigma level in 10 years of observation.

  19. Spiral-like star-forming patterns in CALIFA early-type galaxies

    CERN Document Server

    Gomes, J M; Vílchez, J M; Kehrig, C; Iglesias-Páramo, J; Breda, I; Lehnert, M D; Sánchez, S F; Ziegler, B; Reis, S N dos; Bland-Hawthorn, J; Galbany, L; Bomans, D J; Rosales-Ortega, F F; Walcher, C J; García-Benito, R; Márquez, I; del Olmo, A; Mollá, M; Marino, R A; Catalán-Torrecilla, C; Delgado, R M González; López-Sánchez, Á R

    2015-01-01

    Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 < {\\mu}$_r$ mag/arcsec$^2$ < 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(H\\alpha)$\\simeq$1{\\AA}) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3{\\AA}

  20. Corrugated velocity patterns in the spiral galaxies: NGC 278, NGC 1058, NGC 2500 \\& UGC 3574

    CERN Document Server

    Sánchez-Gil, M Carmen; Pérez, Enrique

    2015-01-01

    We address the study of the \\Ha\\ vertical velocity field in a sample of four nearly face-on galaxies using long slit spectroscopy taken with the ISIS spectrograph attached to the WHT at the Roque de los Muchachos Observatory (Spain). The spatial structure of the velocity vertical component shows a radial corrugated pattern with spatial scales higher or within the order of { one} kiloparsec. The gas is mainly ionized by high-energy photons: only in some locations of NGC~278 and NGC~1058 is there some evidence of ionization by low-velocity shocks, which, in the case of NGC~278, could be due to minor mergers. The behaviour of the gas in the neighbourhood of the spiral arms fits, in the majority of the observed cases, with that predicted by the so-called hydraulic bore mechanism, where a thick magnetized disk encounters a spiral density perturbation. The results obtained show that it is { difficult to explain the \\Ha\\ large scale velocity field without the presence of a magnetized, thick galactic disk}. Larger sa...

  1. Planetary Nebulae in Face-On Spiral Galaxies. III. Planetary Nebula Kinematics and Disk Mass

    CERN Document Server

    Herrmann, Kimberly A

    2009-01-01

    Much of our understanding of dark matter halos comes from the assumption that the mass-to-light ratio (M/L) of spiral disks is constant. The best way to test this hypothesis is to measure the disk surface mass density directly via the kinematics of old disk stars. To this end, we have used planetary nebulae (PNe) as test particles and have measured the vertical velocity dispersion (sigma_z) throughout the disks of five nearby, low-inclination spiral galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). By using HI to map galactic rotation and the epicyclic approximation to extract sigma_z from the line-of-sight dispersion, we find that, with the lone exception of M101, our disks do have a constant M/L out to ~3 optical scale lengths. However, once outside this radius, sigma_z stops declining and becomes flat with radius. Possible explanations for this behavior include an increase in the disk mass-to-light ratio, an increase in the importance of the thick disk, and heating of th...

  2. Disc colours in field and cluster spiral galaxies at 0.5 ≲z ≲ 0.8

    Science.gov (United States)

    Cantale, Nicolas; Jablonka, Pascale; Courbin, Frédéric; Rudnick, Gregory; Zaritsky, Dennis; Meylan, Georges; Desai, Vandana; De Lucia, Gabriella; Aragón-Salamanca, Alfonso; Poggianti, Bianca M.; Finn, Rose; Simard, Luc

    2016-05-01

    We present a detailed study of the colours of late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 ≲ z ≲ 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed of 96 field disc galaxies. We deconvolved their ground-based V and I images obtained with FORS2 at the VLT with initial spatial resolutions between 0.4 and 0.8 arcsec to achieve a final resolution of 0.1 arcsec with 0.05 arcsec pixels, which is close to the resolution of the ACS at the HST. After removing the central region of each galaxy to avoid pollution by the bulges, we measured the V-I colours of the discs. We find that 50% of cluster spiral galaxies have disc V-I colours redder by more than 1σ of the mean colours of their field counterparts. This is well above the 16% expected for a normal distribution centred on the field disc properties. The prominence of galaxies with red discs depends neither on the mass of their parent cluster nor on the distance of the galaxies to the cluster cores. Passive spiral galaxies constitute 20% of our sample. These systems are not abnormally dusty. They are are made of old stars and are located on the cluster red sequences. Another 24% of our sample is composed of galaxies that are still active and star forming, but less so than galaxies with similar morphologies in the field. These galaxies are naturally located in the blue sequence of their parent cluster colour-magnitude diagrams. The reddest of the discs in clusters must have stopped forming stars more than ~5 Gyr ago. Some of them are found among infalling galaxies, suggesting preprocessing. Our results confirm that galaxies are able to continue forming stars for some significant period of time after being accreted into clusters, and suggest that star formation can decline on seemingly long (1 to 5 Gyr) timescales.

  3. The nature of the UV halo around the spiral galaxy NGC 3628

    Science.gov (United States)

    Baes, Maarten; Viaene, Sébastien

    2016-03-01

    Thanks to deep UV observations with GALEX and Swift, diffuse UV haloes have recently been discovered around galaxies. Based on UV-optical colours, it has been advocated that the UV haloes around spiral galaxies are due to UV radiation emitted from the disc and scattered off dust grains at high latitudes. Detailed UV radiative transfer models that take into account scattering and absorption can explain the morphology of the UV haloes, and they require the presence of an additional thick dust disc next the to traditional thin disc for half of the galaxies in their sample. We test whether such an additional thick dust disc agrees with the observed infrared emission in NGC 3628, an edge-on galaxy with a clear signature of a thick dust disc. We extend the far-ultraviolet radiative transfer models to full-scale panchromatic models. Our model, which contains no fine-tuning, can almost perfectly reproduce the observed spectral energy distribution from UV to mm wavelengths. These results corroborate the interpretation of the extended UV emission in NGC 3628 as scattering off dust grains, and hence of the presence of a substantial amount of diffuse extra-planar dust. A significant caveat, however, is the geometrical simplicity and non-uniqueness of our model: other models with a different geometrical setting could lead to a similar spectral energy distribution. More detailed radiative transfer simulations that compare the model results to images from UV to submm wavelengths are a way to break this degeneracy, as are UV polarisation measurements.

  4. Eventful Evolution of Giant Molecular Clouds in Dynamically Evolving Spiral Arms

    CERN Document Server

    Baba, Junichi; Saitoh, Takayuki R

    2016-01-01

    The formation and evolution of giant molecular clouds (GMCs) in spiral galaxies have been investigated in the traditional framework of the combined quasi-stationary density wave and galactic shock model. However, our understanding of the dynamics of spiral arms is changing from the traditional spiral model to a dynamically evolving spiral model. In this study, we investigate the structure and evolution of GMCs in a dynamically evolving spiral arm using a three-dimensional N-body/hydrodynamic simulation of a barred spiral galaxy at parsec-scale resolution. This simulation incorporated self-gravity, molecular hydrogen formation, radiative cooling, heating due to interstellar far-ultraviolet radiation, and stellar feedback by both HII regions and Type-II supernovae. In contrast to a simple expectation based on the traditional spiral model, the GMCs exhibited no systematic evolutionary sequence across the spiral arm. Our simulation showed that the GMCs behaved as highly dynamic objects with eventful lives involvi...

  5. Stellar Tidal Streams in Spiral Galaxies of the Local Volume: A Pilot Survey with Modest Aperture Telescopes

    CERN Document Server

    Martinez-Delgado, David; Crawford, Ken; Zibbeti, Stefano; Majewski, Steven R; Rix, Hans-Walter; Fliri, Jurgen; Carballo-Bello, Julio A; Bardalez-Gagliuffi, Daniella C; Penarrubia, Jorge; Chonis, Taylor R; Trujillo, Ignacio; Schirmer, Mischa; McDavid, David A

    2010-01-01

    [Abridged] Within the hierarchical framework for galaxy formation, minor merging and tidal interactions are expected to shape large galaxies to the present day. As part of a pilot survey, we have carried out ultra deep, wide field imaging of several isolated spiral galaxies in the Local Volume with data taken at small (D= 0.1-0.5m) robotic telescopes that provide exquisite surface brightness sensitivity. Our observational effort has led to the discovery of six previously undetected giant stellar structures in the halos of these galaxies that are likely associated with debris from tidally disrupted satellites. In addition, we confirm and clarify several enormous stellar over-densities previously reported in the literature, but never before interpreted as tidal streams. Our collection of galaxies presents an assortment of tidal phenomena exhibiting strikingly diverse morphological characteristics. In addition to identifying great circle-like features that resemble the Sagittarius stream surrounding the Milky Wa...

  6. Shape of the oxygen abundance profiles in CALIFA face-on spiral galaxies

    CERN Document Server

    Sánchez-Menguiano, L; Pérez, I; García-Benito, R; Husemann, B; Mast, D; Mendoza, A; Ruiz-Lara, T; Ascasibar, Y; Bland-Hawthorn, J; Cavichia, O; Díaz, A I; Florido, E; Galbany, L; Delgado, R M Gónzalez; Kehrig, C; Marino, R A; Márquez, I; Masegosa, J; Méndez-Abreu, J; Mollá, M; del Olmo, A; Pérez, E; Sánchez-Blázquez, P; Stanishev, V; Walcher, C J; López-Sánchez, Á R

    2016-01-01

    We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3-4 disc effective radii (r$_e$). We confirm the results obtained from classical HII region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 r$_e$ of $\\alpha_{O/H} = -\\,0.075\\,\\rm{dex}/r_e$ with a scatter of $\\sigma = 0.016\\,\\rm{dex}/r_e$ when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude...

  7. Spatial distribution of far infrared emission in spiral galaxies; 1, relation with radio continuum emission

    CERN Document Server

    Mayya, Y D

    1997-01-01

    We use high resolution IRAS and 20 cm radio continuum (RC) images of a sample of 22 spiral galaxies to study the correlation between the far infra-red (FIR) and RC emissions within the galactic disks. A combination of exponential and gaussian profiles rather than a single exponential profile is found to be a better representation of the observed intensity profiles in the two bands. The gaussian component, which we show is not due to the effects of limited beam-resolution, contains more than 60% of the total flux in majority of the galaxies. The dominance of the gaussian component suggests that the nuclear star forming regions and the bulge stars are more important contributors to the emission in the two bands, rather than the outer exponential stellar disks. The RC profile is flatter compared to the FIR profile, resulting in a decrease of their ratio, Q60, away from the center. However, the Q60 increases in the extreme outer parts, where the dispersion in the FIR and RC correlation is also higher than in the ...

  8. Stellar populations of classical and pseudo-bulges for a sample of isolated spiral galaxies

    CERN Document Server

    Zhao, Yinghe

    2011-01-01

    In this paper we present the stellar population synthesis results for a sample of 75 bulges in isolated spiral Sb-Sc galaxies, using the spectroscopic data from the Sloan Digital Sky Survey and the STARLIGHT code. We find that both pseudo-bulges and classical bulges in our sample are predominantly composed of old stellar populations, with mean mass-weighted stellar age around 10 Gyr. While the stellar population of pseudo-bulges is, in general, younger than that of classical bulges, the difference is not significant, which indicates that it is hard to distinguish pseudo-bulges from classical bulges, at least for these isolated galaxies, only based on their stellar populations. Pseudo-bulges have star formation activities with relatively longer timescale than classical bulges, indicating that secular evolution is more important in this kind of systems. Our results also show that pseudo-bulges have a lower stellar velocity dispersion than their classical counterparts, which suggests that classical bulges are mo...

  9. The bolometric and UV attenuation in normal spiral galaxies of the Herschel Reference Survey

    CERN Document Server

    Viaene, S; Bendo, G; Boquien, M; Boselli, A; Ciesla, L; Cortese, L; De Looze, I; Eales, S; Fritz, J; Karczewski, O Ł; Madden, S; Smith, M W L; Spinoglio, L

    2016-01-01

    The dust in nearby galaxies absorbs a fraction of the UV-optical-near-infrared radiation produced by stars. This energy is consequently re-emitted in the infrared. We investigate the fraction of the stellar radiation absorbed by spiral galaxies from the HRS by modelling their UV-to-submillimetre spectral energy distributions. Our models provide an attenuated and intrinsic SED from which we find that on average 32 % of all starlight is absorbed by dust. We define the UV heating fraction as the fraction of dust luminosity that comes from absorbed UV photons and find that this is 56 %, on average. This percentage varies with morphological type, with later types having significantly higher UV heating fractions. We find a strong correlation between the UV heating fraction and specific star formation rate and provide a power-law fit. Our models allow us to revisit the IRX-AFUV relations, and derive these quantities directly within a self-consistent framework. We calibrate this relation for different bins of NUV-r c...

  10. A spectral and photometric study of 102 star forming regions in seven spiral galaxies

    CERN Document Server

    Gusev, A S; Piskunov, A E; Kharchenko, N V; Bruevich, V V; Ezhkova, O V; Guslyakova, S A; Lang, V; Shimanovskaya, E V; Efremov, Yu N

    2016-01-01

    We present a study of complexes of young massive star clusters (YMCs), embedded in extragalactic giant HII regions, based on the coupling of spectroscopic with photometric and spectrophotometric observations of about 100 star forming regions in seven spiral galaxies (NGC 628, NGC 783, NGC 2336, NGC 6217, NGC 6946, NGC 7331, and NGC 7678). The complete observational database has been observed and accumulated within the framework of our comprehensive study of extragalactic star forming regions. The current paper presents the last part of either unpublished or refreshed photometric and spectrophotometric observations of the galaxies NGC 6217, NGC 6946, NGC 7331, and NGC 7678. We derive extinctions, chemical abundances, continuum and line emissions of ionised gas, ages and masses for cluster complexes. We find the young massive cluster complexes to have ages no greater than 10 Myr and masses between 10^4Msol and 10^7Msol, and the extinctions A(V) vary between ~ 0 and 3 mag, while the impact of the nebular emissio...

  11. High-Resolution, High Signal-to-Noise, Global H i Spectra of Southern, Extreme Late-Type Spiral Galaxies

    Science.gov (United States)

    Matthews, L. D.; van Driel, W.; Gallagher, J. S., III

    1998-09-01

    We have used the Nançay decimetric radio telescope to obtain high-resolution, high signal-to-noise, global H i spectra of 30 southern, extreme late-type spiral galaxies with V_h Matthews & Gallagher. In Appendix B we present new H i spectra for four additional late-type galaxies. The H i spectra of the extreme late-type spirals have velocity widths characteristic of true, rotationally supported disk galaxies, and most are double-peaked. Nonetheless, the morphologies of the H i profiles are diverse, indicating that disk galaxies with similar H i contents and optical luminosities can have very different H i distributions and/or velocity fields. H i profile type and Hubble type are generally well-correlated for our sample. Seventy-seven percent of our H i profiles show at least some degree of asymmetry; in many cases the stellar disk of these galaxies is also asymmetric. Several of our spectra have an additional H i peak near the systemic velocity, perhaps indicating a gas enhancement in the central regions of the galaxy disk.

  12. The structure of spiral galaxies: radial profiles in stellar Mass-to-Light ratio and the Dark Matter distribution

    CERN Document Server

    Portinari, Laura

    2009-01-01

    The colour and metallicity gradients observed in spiral galaxies suggest that the mass-to-light ratio (M*/L) of the stellar disc is a function of radius. This is indeed predicted by chemo-photometric models of galactic discs. We investigate the distribution of luminous and dark matter in spiral galaxies, taking into account the radial dependence of the stellar M*/L - which is usually assumed to be constant in studies of the mass structure. From the chemo-photometric models of Portinari et al. (2004) and in agreement with the observed radial profiles of galaxy colours, we derive the typical average M*/L profile of the stellar discs of spiral galaxies. We compute the corresponding Variable Mass-to-Light (VML) stellar surface density profile and then the VML disc contribution to the circular velocity. We use the latter, combined with a well studied dark matter velocity profile, to mass model the co-added rotation curves of Persic et al. (1996). By investigating rotation curves in the framework of VML stellar dis...

  13. FORMATION OF DENSE MOLECULAR GAS AND STARS AT THE CIRCUMNUCLEAR STARBURST RING IN THE BARRED GALAXY NGC 7552

    International Nuclear Information System (INIS)

    We present millimeter molecular line complemented by optical observations, along with a reanalysis of archival centimeter H I and continuum data, to infer the global dynamics and determine where dense molecular gas and massive stars preferentially form in the circumnuclear starburst ring of the barred-spiral galaxy NGC 7552. We find diffuse molecular gas in a pair of dust lanes each running along the large-scale galactic bar, as well as in the circumnuclear starburst ring. We do not detect dense molecular gas in the dust lanes, but find such gas concentrated in two knots where the dust lanes make contact with the circumnuclear starburst ring. When convolved to the same angular resolution as the images in dense gas, the radio continuum emission of the circumnuclear starburst ring also exhibits two knots, each lying downstream of an adjacent knot in dense gas. The results agree qualitatively with the idea that massive stars form from dense gas at the contact points, where diffuse gas is channeled into the ring along the dust lanes, and later explode as supernovae downstream of the contact points. Based on the inferred rotation curve, however, the propagation time between the respective pairs of dense gas and centimeter continuum knots is about an order of magnitude shorter than the lifetimes of OB stars. We discuss possible reasons for this discrepancy, and conclude that either the initial mass function is top-heavy or massive stars in the ring do not form exclusively at the contact points where dense molecular gas is concentrated.

  14. Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?

    CERN Document Server

    Cheung, Edmond; Athanassoula, E; Bamford, Steven P; Bell, Eric F; Bosma, A; Cardamone, Carolin N; Casteels, Kevin R V; Faber, S M; Fang, Jerome J; Fortson, Lucy F; Kocevski, Dale D; Koo, David C; Laine, Seppo; Lintott, Chris; Masters, Karen L; Melvin, Thomas; Nichol, Robert C; Schawinski, Kevin; Simmons, Brooke; Smethurst, Rebecca; Willett, Kyle W

    2014-01-01

    We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 1, our findings suggest that large-scale bars have likely never directly been a dominant fueling mechanism for supermassive black hole growth.

  15. THE BULGELESS SEYFERT/LINER GALAXY NGC 3367: DISK, BAR, LOPSIDEDNESS, AND ENVIRONMENT

    International Nuclear Information System (INIS)

    NGC 3367 is a nearby isolated active galaxy that shows a radio jet, a strong bar, and evidence of lopsidedness. We present a quantitative analysis of the stellar and gaseous structure of the galaxy disk and search for evidence of recent interaction. Our study is based on new UBVRI Hα and JHK images and on archive Hα Fabry-Perot and H I Very Large Array data. From a coupled one-dimensional/two-dimensional GALFIT bulge/bar/disk decomposition a (B/D ∼ 0.07-0.1) exponential pseudobulge is inferred in all the observed bands. A near-infrared (NIR) estimate of the bar strength QmaxT(R) = 0.44 places NGC 3367 bar among the strongest ones. The asymmetry properties were studied using (1) the optical and NIR concentration-asymmetry-clumpiness indices, (2) the stellar (NIR) and gaseous (Hα, H I) A1 Fourier mode amplitudes, and (3) the H I-integrated profile and H I mean intensity distribution. While the average stellar component shows asymmetry values close to the average found in the local universe for isolated galaxies, the young stellar component and gas values are largely decoupled showing significantly larger A1 mode amplitudes suggesting that the gas has been recently perturbed and placing NGC 3367 in a global starburst phase. NGC 3367 is devoid of H I gas in the central regions where a significant amount of molecular CO gas exists instead. Our search for (1) faint stellar structures in the outer regions (up to μR ∼ 26 mag arcsec–2), (2) (Hα) star-forming satellite galaxies, and (3) regions with different colors (stellar populations) along the disk all failed. Such an absence is interpreted by using results from recent numerical simulations to constrain either a possible tidal event with an LMC like galaxy to some dynamical times in the past or a very low mass but perhaps gas rich recent encounter. We conclude that a cold flow accretion mode (gas and small/dark galaxies) may be responsible for the nuclear activity and peculiar (young stars and gas) morphology

  16. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Seigar, Marc S. [Department of Physics, University of Minnesota Duluth, 1023 University Drive, MWAH 371, Duluth, MN 55812-3009 (United States); Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel [Arkansas Center for Space and Planetary Sciences, 202 Field House, University of Arkansas, Fayetteville, AR 72701 (United States)

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  17. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    CERN Document Server

    Seigar, Marc S; Berrier, Joel; Kennefick, Daniel

    2014-01-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6-$\\mu$m imaging data and observed H$\\alpha$ rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  18. Constraining Dark Matter Halo Profiles and Galaxy Formation Models Using Spiral Arm Morphology. II. Dark and Stellar Mass Concentrations for 13 Nearby Face-on Galaxies

    Science.gov (United States)

    Seigar, Marc S.; Davis, Benjamin L.; Berrier, Joel; Kennefick, Daniel

    2014-11-01

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  19. Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. II. Dark and stellar mass concentrations for 13 nearby face-on galaxies

    International Nuclear Information System (INIS)

    We investigate the use of spiral arm pitch angles as a probe of disk galaxy mass profiles. We confirm our previous result that spiral arm pitch angles (P) are well correlated with the rate of shear (S) in disk galaxy rotation curves. We use this correlation to argue that imaging data alone can provide a powerful probe of galactic mass distributions out to large look-back times. We then use a sample of 13 galaxies, with Spitzer 3.6 μm imaging data and observed Hα rotation curves, to demonstrate how an inferred shear rate coupled with a bulge-disk decomposition model and a Tully-Fisher-derived velocity normalization can be used to place constraints on a galaxy's baryon fraction and dark matter halo profile. Finally, we show that there appears to be a trend (albeit a weak correlation) between spiral arm pitch angle and halo concentration. We discuss implications for the suggested link between supermassive black hole (SMBH) mass and dark halo concentration, using pitch angle as a proxy for SMBH mass.

  20. The formation and evolution of bars in low surface brightness galaxies with cold dark matter halos

    CERN Document Server

    Mayer, L; Mayer, Lucio; Wadsley, James

    2003-01-01

    We perform several high resolution N-Body/SPH simulations of low surface brightness galaxies (LSBs) embedded in cold dark matter halos to study how likely is bar formation in such systems. The behavior of various collisionless galaxy models is studied both in isolation and in the presence of a large perturbing satellite. We also consider models with a dominant gaseous component in the disk. We find that in general bar formation requires disk masses at least a factor of 2 higher than those inferred for LSBs under the assumption of a normal stellar mass-to-light ratio. Low surface density stellar disks contributing less than 10% of the total virial mass are stable within NFW halos spanning a range of concentrations. However, a purely gaseous disk can form a bar even for quite low masses and for realistic temperatures provided that cooling is very efficient (we adopt an isothermal equation of state) and that the halo has a very low concentration, c < 5. The bars that form in these LSB models are shorter than ...

  1. The HST/ACS Coma Cluster Survey. VIII. Barred Disk Galaxies in the Core of the Coma Cluster

    CERN Document Server

    Marinova, Irina; Weinzirl, Tim; Erwin, Peter; Trentham, Neil; Ferguson, Henry C; Hammer, Derek; Brok, Mark den; Graham, Alister W; Carter, David; Balcells, Marc; Goudfrooij, Paul; Guzman, Rafael; Hoyos, Carlos; Mobasher, Bahram; Mouhcine, Mustapha; Peletier, Reynier F; Peng, Eric; Kleijn, Gijs Verdoes

    2012-01-01

    (ABRIDGED) We use high resolution (~0.1") F814W ACS images from the HST ACS Treasury survey of the Coma cluster at z~0.02 to study bars in massive disk galaxies (S0s), and in dwarf galaxies in the Coma core. Our study helps constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. (1) We characterize the fraction and properties of bars in a sample of 32 bright (M_V 10^9.5 M_sun) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. Measuring the S0 bar fraction must be handled carefully, as the results depend on the method used: the bar fraction for bright S0s in the Coma core is 50%+/-11%, 65%+/-11%, and 60%+/-11% for three methods of bar detection: strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (Coma core, A901/902, Virgo). We find that the bar fraction among bright S0 ...

  2. Erratum: Precision Velocity Fields in Spiral Galaxies. I. Noncircular Motions and rms Noise in Disks

    Science.gov (United States)

    Beauvais, Charles; Bothun, G.

    2000-05-01

    In the paper ``Precision Velocity Fields in Spiral Galaxies. I. Noncircular Motions and rms Noise in Disks'' by Charles Beauvais and G. Bothun (ApJS, 125, 99) the abstract was incorrect. The corrected abstract is as follows: Imaging Fabry-Perot data have been acquired for a sample of spiral galaxies from which two-dimensional velocity fields have been constructed on a subkiloparsec resolution scale. These velocity fields are then examined for evidence of noncircular motions. Individual spectra are extracted and the resultant line profiles are fitted with Voigt, Gaussian, and Lorentzian functions. Gaussians are shown to provide a better model for simultaneously fitting a large number of line profiles, successfully fitting a higher fraction. The kinematic disk (i.e., tilted ring) modeling procedure is studied in detail and is shown to accurately recover the underlying rotational structure of galactic disks. The process of obtaining rotation curves from full two-dimensional velocity data is examined. Small-scale ``bumps and wiggles'' on the rotation curves are shown to be due to the inclusion of noncircular motions. Use of the rotation curve estimate returned by the modeling procedure rather than deprojection of the velocity field is recommended to avoid their inclusion. Investigation of the symmetry of the major- and minor-axis rotation curves reveal strong evidence of nonconcentric gas orbits with the maximum center shift of ~300 pc. Comparisons between kinematic and photometric structure (e.g., position angles, inclinations, centers) show considerable noise on small scales. Although large-scale averages are in agreement, this noise is a matter of some concern in the application of the Tully-Fisher method to disk galaxies. Moreover, cases of significant misalignment in position angle between the inner and outer disks are seen in two of the sample galaxies and may indicate the transition between luminous and dark-matter-dominated regions (i.e., where the maximum disk

  3. GIANT MOLECULAR CLOUDS AND STAR FORMATION IN THE NON-GRAND DESIGN SPIRAL GALAXY NGC 6946

    International Nuclear Information System (INIS)

    We present high spatial resolution observations of giant molecular clouds (GMCs) in the eastern part of the nearby spiral galaxy NGC 6946 obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We have observed CO(1 → 0), CO(2 → 1) and 13CO(1 → 0), achieving spatial resolutions of 5.''4 × 5.''0, 2.''5 × 2.''0, and 5.''6 × 5.''4, respectively, over a region of 6 × 6 kpc. This region extends from 1.5 kpc to 8 kpc galactocentric radius, thus avoiding the intense star formation in the central kpc. We have recovered short-spacing u-v components by using single dish observations from the Nobeyama 45 m and IRAM 30 m telescopes. Using the automated CPROPS algorithm, we identified 45 CO cloud complexes in the CO(1 → 0) map and 64 GMCs in the CO(2 → 1) maps. The sizes, line widths, and luminosities of the GMCs are similar to values found in other extragalactic studies. We have classified the clouds into on-arm and inter-arm clouds based on the stellar mass density traced by the 3.6 μm map. Clouds located on-arm present in general higher star formation rates than clouds located in inter-arm regions. Although the star formation efficiency shows no systematic trend with galactocentric radius, some on-arm clouds—which are more luminous and more massive compared to inter-arm GMCs—are also forming stars more efficiently than the rest of the identified GMCs. We find that these structures appear to be located in two specific regions in the spiral arms. One of them shows a strong velocity gradient, suggesting that this region of high star formation efficiency may be the result of gas flow convergence.

  4. Large scale star formation in galaxies. II. The spirals NGC 3377A, NGC 3507 and NGC 4394

    CERN Document Server

    Vicari, A; Capuzzo-Dolcetta, R; Wyder, T K; Arrabito, G

    2001-01-01

    The identification of young star groupings (YSG) in the three spiral galaxies NGC 3377A, NGC 3507, NGC 4394 is obtained by mean of the statistical method described in Paper I. We find 83, 90, 185 YSGs, respectively. An identification map of YSGs, as well as their size distribution, their B-luminosity function, their surface luminosity density radial behaviour, are presented and comparatively discussed. These data, in addition to those in Paper I, constitute a first sample suitable for seeking correlations among properties of galaxies and their YSG, which we briefly discuss here.

  5. Evolution in the Dust Lane Fraction of Edge-on L* Spiral Galaxies since z=0.8

    CERN Document Server

    Holwerda, B W; Radburn-Smith, D; de Jong, R S; Guhathakurta, P; Koekemoer, A; Allen, R J; Böker, T

    2012-01-01

    The presence of a well-defined and narrow dust lane in an edge-on spiral galaxy is the observational signature of a thin and dense molecular disk, in which gravitational collapse has overcome turbulence. Using a sample of galaxies out to z~1 extracted from the COSMOS survey, we identify the fraction of massive disks that display a dust lane. Our goal is to explore the evolution in the stability of the molecular ISM disks in spiral galaxies over a cosmic timescale. We check the reliability of our morphological classifications against changes in restframe wavelength, resolution, and cosmic dimming with (artificially redshifted) images of local galaxies from SDSS. We find that the fraction of L* disks with dust lanes in COSMOS is consistent with the local fraction (~80%) out to z~0.7. At z=0.8, the dust lane fraction is only slightly lower. A somewhat lower dust lane fraction in starbursting galaxies tentatively supports the notion that a high specific star formation rate can efficiently destroy or inhibit a den...

  6. Spiral-induced velocity and metallicity patterns in a cosmological zoom simulation of a Milky Way-sized galaxy

    Science.gov (United States)

    Grand, Robert J. J.; Springel, Volker; Kawata, Daisuke; Minchev, Ivan; Sánchez-Blázquez, Patricia; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rüdiger; Campbell, David J. R.

    2016-07-01

    We use a high-resolution cosmological zoom simulation of a Milky Way-sized halo to study the observable features in velocity and metallicity space associated with the dynamical influence of spiral arms. For the first time, we demonstrate that spiral arms, that form in a disc in a fully cosmological environment with realistic galaxy formation physics, drive large-scale systematic streaming motions. In particular, on the trailing edge of the spiral arms the peculiar galactocentric radial and azimuthal velocity field is directed radially outward and azimuthally backward, whereas it is radially inward and azimuthally forward on the leading edge. Owing to the negative radial metallicity gradient, this systematic motion drives, at a given radius, an azimuthal variation in the residual metallicity that is characterized by a metal-rich trailing edge and a metal-poor leading edge. We show that these signatures are theoretically observable in external galaxies with integral field unit instruments such as VLT/MUSE, and if detected, would provide evidence for large-scale systematic radial migration driven by spiral arms.

  7. Star-forming complexes and the spiral structure of our Galaxy

    Science.gov (United States)

    Russeil, D.

    2003-01-01

    We have carried out a multiwavelength study of the plane of our Galaxy in order to establish a star-forming-complex catalogue which is as complete as possible. Features observed include Hα , H109alpha , CO, the radio continuum and absorption lines. For each complex we have determined the position, the systemic velocity, the kinematic distance and, when possible, the stellar distance and the corresponding uncertainties. All of these parameters were determined as homogeneously as possible, in particular all the stellar distances have been (re)calculated with the same calibration and the kinematic distances with the same mean Galactic rotation curve. Through the complexes with stellar distance determination, a rotation curve has been fitted. It is in good agreement with the one of Brand & Blitz (1993). We also investigated the residual velocities relative to the circular rotation model. We find that departures exist over large areas of the arms, with different values from one arm to another. From our data and in good agreement with previous studies, the Galactic warp is observed. It does not seem correlated with the departures from circular rotation. Finally, as segment-like features are noted from the complexes' distribution, we tried to find if they are indicative of a larger underlying structure. Then, we attempted to interpret the complexes' distribution in terms of spiral structure by fitting models with two, three and four logarithmic spiral arms. The four-arm model seems more appropriate to represent the grand design of our Galaxy. In this model the Norma arm and the external arm appear as being the two extremities of a single arm called the Norma-Cygnus arm. The new data and fitted model confirm the four-segment model of Georgelin & Georgelin (1976), clarifying the arms' design and extension and doubling their known length. Based on observations collected at the European Southern Observatory. Tables 1 and 3 (table1.ps and table3.txt) are available in

  8. Spiral symmetry

    CERN Document Server

    Hargittai, Istvan

    1992-01-01

    From the tiny twisted biological molecules to the gargantuan curling arms of many galaxies, the physical world contains a startling repetition of spiral patterns. Today, researchers have a keen interest in identifying, measuring, and defining these patterns in scientific terms. Spirals play an important role in the growth processes of many biological forms and organisms. Also, through time, humans have imitated spiral motifs in their art forms, and invented new and unusual spirals which have no counterparts in the natural world. Therefore, one goal of this multiauthored book is to stress the c

  9. BUILDING LATE-TYPE SPIRAL GALAXIES BY IN-SITU AND EX-SITU STAR FORMATION

    International Nuclear Information System (INIS)

    We analyze the formation and evolution of the stellar components in ''Eris'', a 120 pc resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of ''in-situ'' (within the main host) and ''ex-situ'' (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: (1) approximately 70% of today's stars formed in-situ; (2) more than two thirds of the ex-situ stars formed within satellites after infall; (3) the majority of ex-situ stars are found today in the disk and in the bulge; (4) the stellar halo is dominated by ex-situ stars, whereas in-situ stars dominate the mass profile at distances ≲ 5 kpc from the center at high latitudes; and (5) approximately 25% of the inner, r ≲ 20 kpc, halo is composed of in-situ stars that have been displaced from their original birth sites during Eris' early assembly history

  10. BUILDING LATE-TYPE SPIRAL GALAXIES BY IN-SITU AND EX-SITU STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Pillepich, Annalisa [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Madau, Piero [Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High St., Santa Cruz, CA 95064 (United States); Mayer, Lucio [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-9057 Zurich (Switzerland)

    2015-02-01

    We analyze the formation and evolution of the stellar components in ''Eris'', a 120 pc resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of ''in-situ'' (within the main host) and ''ex-situ'' (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: (1) approximately 70% of today's stars formed in-situ; (2) more than two thirds of the ex-situ stars formed within satellites after infall; (3) the majority of ex-situ stars are found today in the disk and in the bulge; (4) the stellar halo is dominated by ex-situ stars, whereas in-situ stars dominate the mass profile at distances ≲ 5 kpc from the center at high latitudes; and (5) approximately 25% of the inner, r ≲ 20 kpc, halo is composed of in-situ stars that have been displaced from their original birth sites during Eris' early assembly history.

  11. Gaseous Flows in Galaxies

    CERN Document Server

    Combes, F

    2007-01-01

    The gas component plays a major role in the dynamics of spiral galaxies, because of its dissipative character, and its ability to exchange angular momentum with stars in the disk. Due to its small velocity dispersion, it triggers gravitational instabilities, and the corresponding non-axisymmetric patterns produce gravity torques, which mediate these angular momentum exchanges. When a srong bar pattern develops with the same pattern speed all over the disk, only gas inside corotation can flow towards the center. But strong bars are not long lived in presence of gas, and multiple-speed spiral patterns can develop between bar phases, and help the galaxy to accrete external gas flowing from cosmic filaments. The gas is then intermittently driven to the galaxy center, to form nuclear starbursts and fuel an active nucleus. The various time-scales of these gaseous flows are described.

  12. Kinematics and excitation of the nuclear spiral in the active galaxy Arp 102B

    CERN Document Server

    Couto, Guilherme S; Axon, David J; Robinson, Andrew; Kharb, Preeti; Riffel, Rogemar A

    2013-01-01

    We present a two-dimensional analysis of the gaseous excitation and kinematics of the inner 2.5 x 1.7 kpc^2 of the LINER/Seyfert 1 galaxy Arp 102B, from optical spectra obtained with the GMOS integral field spectrograph on the Gemini North telescope at a spatial resolution of 250 pc. Emission-line flux maps show the same two-armed nuclear spiral we have discovered in previous observations with the HST-ACS camera. One arm reaches 1 kpc to the east and the other 500 pc to the west, with a 8.4 GHz VLA bent radio jet correlating with the former. The gas density is highest (500 - 900 cm^(-3)) at the nucleus and in the northern border of the east arm, at a region where the radio jet seems to be deflected. Channel maps show blueshifts but also some redshifts at the eastern arm and jet location which can be interpreted as originated in the front and back walls of an outflow pushed by the radio jet, suggesting also that the outflow is launched close to the plane of the sky. We estimate a mass outflow rate along the ea...

  13. The Influence of Bars on Nuclear Activity

    CERN Document Server

    Ho, L C; Sargent, W L W; Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W.

    1997-01-01

    We test ideas on fueling of galactic nuclei by bar-driven inflow by comparing the detection rate and intensity of nuclear H II regions and AGNs among barred and unbarred galaxies in a sample of over 300 spirals selected from our recent optical spectroscopic survey of nearby galaxies. Among late-type spirals (Sc-Sm), but not early-type (S0/a-Sbc), we observe in the barred group a very marginal increase in the detection rate of H II nuclei and a corresponding decrease in the incidence of AGNs. The minor differences in the detection rates, however, are statistically insignificant, most likely stemming from selection effects and not from a genuine influence from the bar. The presence of a bar seems to have no noticeable impact on the likelihood of a galaxy to host either nuclear star formation or an AGN. The nuclei of early-type barred spirals do exhibit measurably higher star-formation rates than their unbarred counterparts, as indicated by either the luminosity or the equivalent width of H-alpha emission. By co...

  14. The BaLROG project - II. Quantifying the influence of bars on the stellar populations of nearby galaxies

    Science.gov (United States)

    Seidel, M. K.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Sánchez-Blázquez, P.; Pérez, I.; Peletier, R.; Vazdekis, A.

    2016-08-01

    We continue the exploration of the BaLROG (Bars in Low Redshift Optical Galaxies) sample: 16 large mosaics of barred galaxies observed with the integral field unit Spectrographic Areal Unit for Research on Optical Nebulae. We quantify the influence of bars on the composition of the stellar component. We derive line-strength indices of H β, Fe5015 and Mgb. Based on single stellar population (SSP) models, we calculate ages, metallicities and [Mg/Fe] abundances and their gradients along the bar major and minor axes. The high spatial resolution of our data allows us to identify breaks among index and SSP profiles, commonly at 0.13 ± 0.06 bar length, consistent with kinematic features. Inner gradients are about 10 times steeper than outer gradients and become larger when there is a central rotating component, implying that the gradients are not independent of dynamics and orbits. Central ages appear to be younger for stronger bars. Yet, the bar regions are usually old. We find a flattening of the iron (Fe5015) and magnesium (Mgb) outer gradients along the bar major axis, translating into a flattening of the metallicity gradient. This gradient is found to be 0.03 ± 0.07 dex kpc-1 along the bar major axis while the mean value of the bar minor axis compares well with that of an unbarred control sample and is significantly steeper, namely -0.20 ± 0.04 dex kpc-1. These results confirm recent simulations and discern the important localized influence of bars. The elevated [Mg/Fe] abundances of bars and bulges compared to the lower values of discs suggest an early formation, in particular for early-type galaxies.

  15. Analytical forms of chaotic spiral arms

    Science.gov (United States)

    Harsoula, M.; Efthymiopoulos, C.; Contopoulos, G.

    2016-07-01

    We develop an analytical theory of chaotic spiral arms in galaxies. This is based on the Moser theory of invariant manifolds around unstable periodic orbits. We apply this theory to the chaotic spiral arms, which start from the neighbourhood of the Lagrangian points L1 and L2 at the end of the bar in a barred-spiral galaxy. The series representing the invariant manifolds starting at the Lagrangian points L1, L2, or unstable periodic orbits around L1 and L2, yield spiral patterns in the configuration space. These series converge in a domain around every Lagrangian point, called `Moser domain', and represent the orbits that constitute the chaotic spiral arms. In fact, these orbits are not only along the invariant manifolds, but also in a domain surrounding the invariant manifolds. We show further that orbits starting outside the Moser domain but close to it converge to the boundary of the Moser domain, which acts as an attractor. These orbits stay for a long time close to the spiral arms before escaping to infinity.

  16. Practical application of KAM theory to galactic dynamics: II. Application to weakly chaotic orbits in barred galaxies

    CERN Document Server

    Weinberg, Martin D

    2015-01-01

    Owing to the pioneering work of Contopoulos, a strongly barred galaxy is known to have irregular orbits in the vicinity of the bar. By definition, irregular orbits can not be represented by action-angle tori everywhere in phase space. This thwarts perturbation theory and complicates our understanding of their role in galaxy structure and evolution. This paper provides a qualitative introduction to a new method based on KAM theory for investigating the morphology of regular and irregular orbits based on direct computation of tori described in Paper 1 and applies it to a galaxy disc bar. Using this method, we find that much of the phase space inside of the bar radius becomes chaotic for strong bars, excepting a small region in phase space between the ILR and corotation resonances for orbits of moderate ellipticity. This helps explain the preponderance of moderately eccentric bar-supporting orbits as the bar strength increases. This also suggests that bar strength may be limited by chaos! The chaos results from ...

  17. Deep HI observations of the surroundings of ram pressure stripped Virgo spiral galaxies - Where is the stripped gas?

    CERN Document Server

    Vollmer, B

    2006-01-01

    Deep Effelsberg 100-m HI observations of 5 HI deficient Virgo spiral galaxies are presented. No new extended HI tail is found in these galaxies. The already known HI tail north of NGC 4388 does not significantly extend further than a WSRT image has shown. Based on the absence of HI tails in a sample of 6 Virgo spiral galaxies and a balance of previous detections of extraplanar gas in the targeted galaxies we propose a global picture where the outer gas disk (beyond the optical radius R_25) is removed much earlier than expected by the classical ram pressure criterion. Based on the two-phase nature of atomic hydrogen located in a galactic disk, we argue that the warm diffuse HI in the outer galactic disk is evaporated much more rapidly than the cold dense HI. Therefore, after a ram pressure stripping event we can only observe atomic hydrogen which was cold and dense before it was removed from the galactic disk. This global picture is consistent with all available observations. We detect between 0.3% and 20% of ...

  18. Two Populations of Old Star Clusters in the Spiral Galaxy M101 Based on HST/ACS Observations

    CERN Document Server

    Simanton, Lesley A; Whitmore, Bradley C

    2015-01-01

    We present a new photometric catalog of 326 candidate globular clusters (GCs) in the nearby spiral galaxy M101, selected from B, V, and I Hubble Space Telescope Advanced Camera for Surveys images. The luminosity function (LF) of these clusters has an unusually large number of faint sources compared with GCLFs in many other spiral galaxies. Accordingly, we separate and compare the properties of "bright" (M_V -6.5; one magnitude fainter than the expected GC peak) clusters within our sample. The LF of the bright clusters is well fit by a peaked distribution similar to those observed in the Milky Way (MW) and other galaxies. These bright clusters also have similar size (r_{eff}) and spatial distributions as MW GCs. The LF of the faint clusters, on the other hand, is well described by a power law, dN(L_V)/dL_V proportional to L_V^alpha with alpha = -2.6 plus or minus 0.3, similar to those observed for young and intermediate-age cluster systems in star forming galaxies. We find that the faint clusters have larger ...

  19. High-resolution, 3D radiative transfer modeling : I. The grand-design spiral galaxy M51

    CERN Document Server

    De Looze, Ilse; Baes, Maarten; Bendo, George J; Cortese, Luca; Boquien, Médéric; Boselli, Alessandro; Camps, Peter; Cooray, Asantha; Cormier, Diane; Davies, Jon I; De Geyter, Gert; Hughes, Thomas M; Jones, Anthony P; Karczewski, Oskar L; Lebouteiller, Vianney; Lu, Nanyao; Madden, Suzanne C; Rémy-Ruyer, Aurélie; Spinoglio, Luigi; Smith, Matthew W L; Viaene, Sebastien; Wilson, Christine D

    2014-01-01

    Context: Dust reprocesses about half of the stellar radiation in galaxies. The thermal re-emission by dust of absorbed energy is considered driven merely by young stars and, consequently, often applied to trace the star formation rate in galaxies. Recent studies have argued that the old stellar population might anticipate a non-negligible fraction of the radiative dust heating. Aims: In this work, we aim to analyze the contribution of young (< 100 Myr) and old (~ 10 Gyr) stellar populations to radiative dust heating processes in the nearby grand-design spiral galaxy M51 using radiative transfer modeling. High-resolution 3D radiative transfer (RT) models are required to describe the complex morphologies of asymmetric spiral arms and clumpy star-forming regions and model the propagation of light through a dusty medium. Methods: In this paper, we present a new technique developed to model the radiative transfer effects in nearby face-on galaxies. We construct a high-resolution 3D radiative transfer model with...

  20. CO(J = 3-2) on-the-fly mapping of the nearby spiral galaxies NGC 628 and NGC 7793: Spatially resolved CO(J = 3-2) star-formation law

    Science.gov (United States)

    Muraoka, Kazuyuki; Takeda, Miho; Yanagitani, Kazuki; Kaneko, Hiroyuki; Nakanishi, Kouichiro; Kuno, Nario; Sorai, Kazuo; Tosaki, Tomoka; Kohno, Kotaro

    2016-04-01

    We present the results of CO(J = 3-2) on-the-fly mappings of two nearby non-barred spiral galaxies, NGC 628 and NGC 7793, with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25″. We successfully obtained global distributions of CO(J = 3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially resolved (sub-kpc) relationship between CO(J = 3-2) luminosities (L^' }_CO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of a JCMT (James Clerk Maxwell Telescope) Nearby Galaxy Legacy Survey sample. We found a striking linear L^' }_CO(3-2)-LIR correlation over the four orders of magnitude, and the correlation is consistent even with that for ultraluminous IR galaxies and submillimeter-selected galaxies. In addition, we examined the spatially resolved relationship between CO(J = 3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that for Giant Molecular Clouds in M 33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with ˜1 dex scatter. We conclude that the CO(J = 3-2) star-formation law (i.e., linear L^' }_CO(3-2)-LIR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies; from spatially resolved nearby galaxy disks to distant IR-luminous galaxies, within ˜1 dex scatter.

  1. The spatially resolved Kennicutt-Schmidt relation in the H I-dominated regions of spiral and dwarf irregular galaxies

    Science.gov (United States)

    Roychowdhury, Sambit; Huang, Mei-Ling; Kauffmann, Guinevere; Wang, Jing; Chengalur, Jayaram N.

    2015-06-01

    We study the Kennicutt-Schmidt relation between average star formation rate (SFR) and average cold gas surface density in the H I-dominated ISM of nearby spiral and dwarf irregular galaxies. We divide galaxies into grid cells varying from sub-kpc to tens of kpc in size. Grid-cell measurements of low SFRs using Hα emission can be biased and scatter may be introduced because of non-uniform sampling of the IMF or because of stochastically varying star formation. In order to alleviate these issues, we use far-ultraviolet emission to trace SFR, and we sum up the fluxes from different bins with the same gas surface density to calculate the average ΣSFR at a given value of Σgas. We study the resulting Kennicutt-Schmidt relation in 400 pc, 1 kpc and 10 kpc scale grids in nearby massive spirals and in 400 pc scale grids in nearby faint dwarf irregulars. We find a relation with a power-law slope of 1.5 in the H I-dominated regions for both kinds of galaxies. The relation is offset towards longer gas consumption time-scales compared to the molecular-hydrogen-dominated centres of spirals, but the offset is an order of magnitude less than that quoted by earlier studies. Our results lead to the surprising conclusion that conversion of gas to stars is independent of metallicity in the H I-dominated regions of star-forming galaxies. Our observed relations are better fit by a model of star formation based on thermal and hydrostatic equilibrium in the ISM, in which stellar heating and supernova feedback set the thermal and turbulent pressure.

  2. Box/Peanut and Bar structures in edge-on and face-on SDSS nearby galaxies I. Catalogue

    CERN Document Server

    Yoshino, Akira

    2014-01-01

    We investigate Box/Peanut and bar structures in image data of edge-on and face-on nearby galaxies taken from SDSS (Sloan Digital Sky Survey) to present catalogues containing the surface brightness parameters and the morphology classification. About 1700 edge-on galaxies and 2600 face-on galaxies are selected from SDSS DR7 in g, r and i-band. The images of each galaxy are fitted with the model of 2-dimensional surface brightness of S\\'{e}rsic bulge and exponential disk. After removing some irregular data, Box/Peanut, bar and other structures are easily distinguished by eye using residual (observed minus model) images. We find 292 Box/Peanut structures in the 1329 edge-on samples and 630 bar structures in 1890 face-on samples in i-band, after removing some irregular data. Then the fraction of Box/Peanut galaxies is about 22 percent against the edge-on samples, and that of bar is about 33 percent (about 50 percent if 629 elliptical galaxies are removed) against the face-on samples. Furthermore the strengths of t...

  3. The spiral structure of the Galaxy revealed by CS sources and evidence for the 4:1 resonance

    CERN Document Server

    Lepine, J R D; Abraham, Zulema; Junqueira, T C; Mishurov, Yu N

    2010-01-01

    We present a map of the spiral structure of the Galaxy, as traced by molecular CS emission associated with IRAS sources which are believed to be compact HII regions. The CS line velocities are used to determine the kinematic distances of the sources, in order to investigate their distribution in the galactic plane. This allows us to use 870 objects to trace the arms, a number larger than that of previous studies based on classical HII regions. The distance ambiguity of the kinematic distances, when it exists, is solved by different procedures, including the latitude distribution and an analysis of the longitude-velocity diagram. The well defined spiral arms are seen to be confined inside the co-rotation radius, as is often the case in spiral galaxies. We identify a square-shaped sub-structure in the CS map with that predicted by stellar orbits at the 4:1 resonance (4 epicycle oscillations in one turn around the galactic center). The sub-structure is found at the expected radius, based on the known pattern rot...

  4. CO(J=3-2) On-the-fly Mapping of the Nearby Spiral Galaxies NGC 628 and NGC 7793: Spatially-resolved CO(J=3-2) Star-formation Law

    CERN Document Server

    Muraoka, Kazuyuki; Yanagitani, Kazuki; Kaneko, Hiroyuki; Nakanishi, Kouichiro; Kuno, Nario; Sorai, Kazuo; Tosaki, Tomoka; Kohno, Kotaro

    2015-01-01

    We present the results of CO(J=3-2) on-the-fly mappings of two nearby non-barred spiral galaxies NGC 628 and NGC 7793 with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25". We successfully obtained global distributions of CO(J=3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially-resolved (sub-kpc) relationship between CO(J=3-2) luminosities (L'CO(3-2)) and infrared (IR) luminosities (LIR) for NGC 628, NGC 7793, and M 83, and compared it with global luminosities of JCMT Nearby Galaxy Legacy Survey sample. We found a striking linear L'CO(3-2)-LIR correlation over the 4 orders of magnitude, and the correlation is consistent even with that for ultraluminous infrared galaxies and submillimeter selected galaxies. In addition, we examined the spatially-resolved relationship between CO(J=3-2) intensities (ICO(3-2)) and extinction-corrected star formation rates (SFRs) for NGC 628, NGC 7793, and M 83, and compared it with that f...

  5. M/L, Hα Rotation Curves, and H I Gas Measurements for 329 Nearby Cluster and Field Spirals. III. Evolution in Fundamental Galaxy Parameters

    Science.gov (United States)

    Vogt, Nicole P.; Haynes, Martha P.; Giovanelli, Riccardo; Herter, Terry

    2004-06-01

    We have conducted a study of optical and H I properties of spiral galaxies (size, luminosity, Hα flux distribution, circular velocity, H I gas mass) to investigate causes (e.g., nature vs. nurture) for variation within the cluster environment. We find H I-deficient cluster galaxies to be offset in fundamental plane space, with disk scale lengths decreased by a factor of 25%. This may be a relic of early galaxy formation, caused by the disk coalescing out of a smaller, denser halo (e.g., higher concentration index) or by truncation of the hot gas envelope due to the enhanced local density of neighbors, although we cannot completely rule out the effect of the gas stripping process. The spatial extent of Hα flux and the B-band radius also decreases, but only in early-type spirals, suggesting that gas removal is less efficient within steeper potential wells (or that stripped late-type spirals are quickly rendered unrecognizable). We find no significant trend in stellar mass-to-light ratios or circular velocities with H I gas content, morphological type, or clustercentric radius, for star-forming spiral galaxies throughout the clusters. These data support the findings of a companion paper that gas stripping promotes a rapid truncation of star formation across the disk and could be interpreted as weak support for dark matter domination over baryons in the inner regions of spiral galaxies.

  6. The spatially resolved Kennicutt-Schmidt relation in the HI dominated regions of spiral and dwarf irregular galaxies

    CERN Document Server

    Roychowdhury, Sambit; Kauffmann, Guinevere; Wang, Jing; Chengalur, Jayaram N

    2015-01-01

    We study the Kennicutt-Schmidt relation between average star formation rate and average cold gas surface density in the Hi dominated ISM of nearby spiral and dwarf irregular galaxies. We divide the galaxies into grid cells varying from sub-kpc to tens of kpc in size. Grid-cell measurements of low SFRs using H-alpha emission can be biased and scatter may be introduced because of non-uniform sampling of the IMF or because of stochastically varying star formation. In order to alleviate these issues, we use far-ultraviolet emission to trace SFR, and we sum up the fluxes from different bins with the same gas surface density to calculate the average $\\Sigma_{SFR}$ at a given value of $\\Sigma_{gas}$. We study the resulting Kennicutt-Schmidt relation in 400 pc, 1 kpc and 10 kpc scale grids in nearby massive spirals and in 400 pc scale grids in nearby faint dwarf irregulars. We find a relation with a power law slope of 1.5 in the HI-dominated regions for both kinds of galaxies. The relation is offset towards longer ga...

  7. Galaxy Zoo: Are bars responsible for the feeding of active galactic nuclei at 0.2 < z < 1.0?

    Science.gov (United States)

    Cheung, Edmond; Trump, Jonathan R.; Athanassoula, E.; Bamford, Steven P.; Bell, Eric F.; Bosma, A.; Cardamone, Carolin N.; Casteels, Kevin R. V.; Faber, S. M.; Fang, Jerome J.; Fortson, Lucy F.; Kocevski, Dale D.; Koo, David C.; Laine, Seppo; Lintott, Chris; Masters, Karen L.; Melvin, Thomas; Nichol, Robert C.; Schawinski, Kevin; Simmons, Brooke; Smethurst, Rebecca; Willett, Kyle W.

    2015-02-01

    We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 1, our findings suggest that large-scale bars have likely never directly been a dominant fuelling mechanism for supermassive black hole growth.

  8. The stellar mass distribution of S$^4$G disk galaxies and the signatures of bar-induced secular evolution

    CERN Document Server

    Díaz-García, Simón; Laurikainen, Eija

    2016-01-01

    We use 3.6 $\\mu$m photometry from the Spitzer Survey of Stellar Structure in Galaxies (S$^{4}$G) to trace the stellar distribution in nearby disk galaxies ($z\\approx0$) with total stellar masses $10^{8.5}\\lesssim M_{\\ast}/M_{\\odot}\\lesssim10^{11}$ and mid-IR Hubble types $-3 \\le T \\le 10$, and to provide observational constraints for galaxy formation models to be checked against. For 1154 galaxies with disk inclinations lower than $65^{\\circ}$, we Fourier decompose and rescale their images to a common frame determined (i) by the size in physical units, (ii) by their disk scalelength, and for 748 barred galaxies (iii) by both the length and orientation of their bars. We stack the resized density profiles and images to obtain statistically representative average stellar disks and bars in bins of $M_{\\ast}$ and $T$. We also calculate the mean stellar contribution to the circular velocity. We infer the gravitational potentials from the synthetic bars to obtain the tangential-to-radial force ratio ($Q_{\\rm T}$) an...

  9. Infrared Survey of Pulsating Giant Stars in the Spiral Galaxy M33: Dust Production, Star Formation History, and Galactic Structure

    CERN Document Server

    Javadi, Atefeh; Mirtorabi, Mohammad Taghi

    2011-01-01

    We introduce a near-IR monitoring campaign of the Local Group spiral galaxy M33, carried out with the UK IR Telescope (UKIRT). The pulsating giant stars are identified and their distributions are used to derive the star formation rate as a function of age. We here present the star formation history for the central square kiloparsec. These stars are also important dust factories; we measure their dust production rates from a combination of our data with Spitzer Space Telescope mid-IR photometry.

  10. The spiral structure of the Galaxy revealed by CS sources and evidence for the 4:1 resonance

    OpenAIRE

    Lepine, J. R. D.; Roman-Lopes, A.; Abraham, Zulema; Junqueira, T. C.; Mishurov, Yu. N.

    2010-01-01

    We present a map of the spiral structure of the Galaxy, as traced by molecular CS emission associated with IRAS sources which are believed to be compact HII regions. The CS line velocities are used to determine the kinematic distances of the sources, in order to investigate their distribution in the galactic plane. This allows us to use 870 objects to trace the arms, a number larger than that of previous studies based on classical HII regions. The distance ambiguity of the kinematic distances...

  11. Searching gravitational microlensing events in the galaxy spiral arms by EROS II; Recherche d'evenements de microlentille gravitationnelle dans les bras spiraux de la galaxie avec EROS II

    Energy Technology Data Exchange (ETDEWEB)

    Derue, Frederic [Paris-11 Univ., 91 Orsay (France)

    1999-04-15

    The EROS II experiment is searching for microlensing events due to compact massive objects passing through the line-of-sight of luminous stars. These objects are candidates to explain the baryonic component of Dark Matter in our Galaxy. EROS II was dedicated to different lines-of-sight: Small and Large Magellanic Clouds, Galactic Centre and 4 directions towards the Spiral Arms of the Galaxy. This thesis presents the first search for microlensing towards these last lines-of-sight (about 9 million stars). Simple criteria based on the search for significant fluctuations allowed one to discover a low noise sample of 7 candidates to the microlensing effect, with an average timescale of 50 days. A detailed analysis of the light curve of one candidate allows us to give a confidence interval on its mass 2.7 x 10{sup -3} < M/M{sub 0} < 0.84 at 95% CL. The amplification curve of another candidate shows a modulation which can be interpreted as a microlensing effect acting on a binary source, with an orbital period of P{sub 0} = 50 {+-} 3 days. To improve the knowledge of the distance of the target stars, we have combined observations of EROS II with bibliographic sources on associations of stars linked with the spiral arm features, and we have developed a program to find variable stars. Ten cepheids have thus been found. Distances obtained with different methods are in rough agreement with each other. The average optical depth measured towards the four directions is {tau}-bar = 0.45{sub 0.11}{sup +0.23} x 10{sup -6}. It is compatible with expectations from simple galactic models. The long duration of most events favours interpretation of lensing by objects belonging to the disk instead of the halo. It also seems that some events due to bulge lenses have influenced measurements towards the line-of-sight which is closest to the Galactic Centre. Observation continue towards spiral arms. More accurate measurements should be obtained with increase of statistics, allowing one to

  12. The BaLROG project - II. Quantifying the influence of bars on the stellar populations of nearby galaxies

    CERN Document Server

    Seidel, Marja K; Martínez-Valpuesta, Inma; Sánchez-Blázquez, Patricia; Pérez, Isabel; Peletier, Reynier; Vazdekis, Alexandre

    2016-01-01

    We continue the exploration of the BaLROG (Bars in Low Redshift Optical Galaxies) sample: 16 large mosaics of barred galaxies observed with the integral field unit SAURON. We quantify the influence of bars on the composition of the stellar component. We derive linestrength indices of H${\\beta}$, Fe5015 and Mgb. Based on single stellar population (SSP) models, we calculate ages, metallicities and [Mg/Fe] abundances and their gradients along the bar major and minor axes. The high spatial resolution of our data allows us to identify breaks among index and SSP profiles, commonly at 0.13$\\pm$0.06 bar length, consistent with kinematic features. Inner gradients are about ten times steeper than outer gradients and become larger when there is a central rotating component, implying that the gradients are not independent of dynamics and orbits. Central ages appear to be younger for stronger bars. Yet, the bar regions are usually old. We find a flattening of the iron (Fe5015) and magnesium (Mgb) outer gradients along the...

  13. A search for supernova remnants in the nearby spiral galaxy M 74 (NGC 628)

    Science.gov (United States)

    Sonbaş, E.; Akyüz, A.; Balman, Ş.; Özel, M. E.

    2010-07-01

    An optical search was carried out for supernova remnants (SNRs) in the Sc type nearby spiral galaxy M 74, using ground-based observations at the TUBITAK National Observatory (TUG, Antalya/Turkey) and the Special Astrophysics Observatory (SAO, Russia). Observations were supplemented by the spectral analysis of archived X-ray data from XMM-Newton and Chandra. The survey of M 74 covered ~9 arcmin2 with [S II], Hα, and their continuum filters. Interference filter images of M 74 were obtained the with the 1.5 m Russian Turkish Telescope (RTT150) at TUG and spectral data taken with the 6 m Bolsoi Azimuthal Telescope (BTA) at SAO. The emission nebulae with continuum-subtracted line ratio values of [S II]λλ6716,6731 /Hα ≥ 0.4 are identified as SNRs. Follow-up spectroscopy confirmed optical SNR identifications. We have identified nine new SNR candidates in M 74 with [S II]/Hα ≥ 0.4 as the basic criterion. The [S II]/Hα ratio ranges from 0.40 to 0.91 and Hα intensities from 2.8 × 10-15 erg cm-2 s-1 to 1.7 × 10-14 erg cm-2 s-1. We also present spectral follow-up observations of these SNR candidates, however, we are able to spectrally confirm only three of them (SNR2, SNR3, and SNR5). The lack of confirmation for the rest might come from contamination by the nearby H II emission regions, as well as from the inaccurate positioning of the long slit on these objects. In addition, we searched the XMM-Newton and Chandra Observatory archival data for the X-ray counterparts to the optically identified candidates. We find positional coincidence with only three SNR candidates, SNR1, SNR2, and SNR8. The spectrum of SNR2 yields a shock temperature of 10.8 keV with an ionization timescale of 1.6 × 1010 s cm-3, indicating a relatively young remnant in an early Sedov phase, which is not supported by our optical wavelength analysis. Given the high luminosity of 1039 erg s-1 and the characteristics of the X-ray spectrum, we favor an ultra luminous X-ray source interpretation for

  14. Dust energy balance study of two edge-on spiral galaxies in the Herschel-ATLAS survey

    CERN Document Server

    De Geyter, Gert; De Looze, Ilse; Bendo, George J; Bourne, Nathan; Camps, Peter; Cooray, Asantha; De Zotti, Gianfranco; Dunne, Loretta; Dye, Simon; Eales, Steve A; Fritz, Jacopo; Furlanetto, Cristina; Gentile, Gianfranco; Hughes, Thomas M; Ivison, Rob J; Maddox, Steve J; Michałowski, Michał J; Smith, Matthew W L; Valiante, Elisabetta; Viaene, Sébastien

    2015-01-01

    Interstellar dust in galaxies can be traced either through its extinction effects on the star light, or through its thermal emission at infrared wavelengths. Recent radiative transfer studies of several nearby edge-on galaxies have found an apparent inconsistency in the dust energy balance: the radiative transfer models that successfully explain the optical extinction underestimate the observed fluxes by an average factor of three. We investigate the dust energy balance for IC4225 and NGC5166, two edge-on spiral galaxies observed by the Herschel Space Observatory in the frame of the H-ATLAS survey. We start from models which were constrained from optical data and extend them to construct the entire spectral energy distribution of our galaxies. These predicted values are subsequently compared to the observed far-infrared fluxes. We find that including a young stellar population in the modelling is necessary as it plays a non-negligible part in the heating of the dust grains. While the modelling approach for bo...

  15. Integral Field Spectroscopy surveys of nearby spiral and U-LIRG galaxies

    OpenAIRE

    Rosales-Ortega, F. F.; Arribas, S.; Kennicutt, R. C.

    2011-01-01

    We describe the observations and preliminary results of the gas-phase analysis based on two ongoing, wide-field Integral Field Spectroscopy (IFS) surveys: the PPAK IFS Nearby Galaxies Survey (PINGS), targeting disc galaxies; and the VIMOS-IFU observations of low-z (Ultra)Luminous Infrared Galaxies (U-LIRGs), the local counterpart of massive, dusty high-z star-forming galaxies. We describe how these observations are allowing to discover and characterise abundance differentials between galactic...

  16. Mortality and dust expulsion in early phases of stellar clusters. Evidence from NIR photometry of nearby, spiral galaxies

    CERN Document Server

    Grosboel, P

    2013-01-01

    It is often argued that young stellar clusters suffer a significant infant mortality that is partly related to the expulsion of dust and gas in their early phases caused by radiation pressure from hot stars and supernovae. Near-infrared (J-K)-Mk diagrams of young stellar clusters in nearby spiral galaxies show a bi-modal distribution that is consistent with a fast decline of their intrinsic extinction at an early epoch. The distinct features in the color-magnitude diagrams (CMD) and the fast change of colors for the youngest clusters allow us to place constraints on their early evolutionary phases, including the time scale for the decreasing extinction caused for instance by gas and dust expulsion. Monte Carlo simulations of cluster populations were performed using the power-law distribution function g(M, t) ~ M^a t^gam. Integrated colors were computed from Starburst99 models. The simulated near-infrared CMD were compared with those observed for six grand-design, spiral galaxies using statistical goodness-of-...

  17. An observer's view of simulated galaxies: disc-to-total ratios, bars, and (pseudo-)bulges

    CERN Document Server

    Scannapieco, Cecilia; Jonsson, Patrik; White, Simon D M

    2010-01-01

    We use cosmological hydrodynamical simulations of the formation of Milky Way mass galaxies to study the relative importance of the main stellar components, discs, bulges, and bars, at z=0. The main aim of this work is to understand if estimates of the structural parameters of these components determined from kinematics (as usually done in simulations) agree well with those obtained using a photometric bulge/disc/bar decomposition (as done in observations). To perform such a comparison, we produced synthetic observations of the simulation outputs with the Monte-Carlo radiative transfer code SUNRISE and used the BUDDA code to make 2D photometric decompositions of the resulting images. We find that the kinematic disc-to-total ratio (D/T) estimates are systematically and significantly lower than the photometric ones. While the maximum D/T ratios obtained with the former method are of the order of 0.2, they are typically >0.4, and can be as high as 0.7, according to the latter. The photometric decomposition shows ...

  18. Orbital and escape dynamics in barred galaxies - I. The 2D system

    CERN Document Server

    Jung, Christof

    2016-01-01

    In this paper we use the two-dimensional (2D) version of a new analytical gravitational model in order to explore the orbital as well as the escape dynamics of the stars in a barred galaxy composed of a spherically symmetric central nucleus, a bar, a flat disk and a dark matter halo component. A thorough numerical investigation is conducted for distinguishing between bounded and escaping motion. Furthermore bounded orbits are further classified into non-escaping regular and trapped chaotic using the Smaller ALingment Index (SALI) method. Our aim is to determine the basins of escape through the two symmetrical escape channels around the Lagrange points $L_2$ and $L_3$ and also to relate them with the corresponding distribution of the escape rates of the orbits. We integrate initial conditions of orbits in several types of planes so as to obtain a more complete view of the overall orbital properties of the dynamical system. We also present evidence that the unstable manifolds which guide the orbits in and out t...

  19. First results of a sensitive search for H I envelopes in a complete sample of spiral galaxies: Extensive H I near the isolated Sc I NGC 628

    International Nuclear Information System (INIS)

    Preliminary results of a search with the Arecibo 1000 foot (305 m) telescope for extended H I envelopes surrounding spiral galaxies show that column densities N(H I)> or =3 x 1018 cm-2 at 2--3 Holmberg radii (R/sub Ho/) are not common. Our sample includes all galaxies of Hubble type later than SO, with optical major-axis diameter greater than 7', and with declination 30--350, and recessional velocity greater than 200 km s-1

  20. Hot Disks And Delayed Bar Formation

    CERN Document Server

    Sheth, Kartik; Elmegreen, Debra Meloy; Elmegreen, Bruce G; Athanassoula, E; Weiner, Ben

    2012-01-01

    We present observational evidence for the inhibition of bar formation in dispersion-dominated (dynamically hot) galaxies by studying the relationship between galactic structure and host galaxy kinematics in a sample of 257 galaxies between 0.1 $<$ z $\\leq$ 0.84 from the All-Wavelength Extended Groth Strip International Survey (AEGIS) and the Deep Extragalactic Evolutionary Probe 2 (DEEP2) survey. We find that bars are preferentially found in galaxies that are massive and dynamically cold (rotation-dominated) and on the stellar Tully-Fisher relationship, as is the case for barred spirals in the local Universe. The data provide at least one explanation for the steep ($\\times$3) decline in the overall bar fraction from z=0 to z=0.84 in L$^*$ and brighter disks seen in previous studies. The decline in the bar fraction at high redshift is almost exclusively in the lower mass (10 $<$ log M$_{*}$(\\Msun)$<$ 11), later-type and bluer galaxies. A proposed explanation for this "downsizing" of the bar formation ...

  1. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    CERN Document Server

    de Souza, R S; Krone-Martins, A; Cameron, E; Coelho, P; Hattab, M W; de Val-Borro, M; Hilbe, J M; Elliott, J; Hagen, A

    2016-01-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, $M_{200}$, and the normalized cluster centric distance, $r/r_{200}$. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control for the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within a HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g., whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a...

  2. The Millennium Galaxy Catalogue: The severe attenuation of bulge flux by dusty spiral discs

    CERN Document Server

    Driver, Simon P

    2007-01-01

    Using the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination. Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions (tau_B^f=3.8+/-0.7). As a consequence the measured B-band fluxes of bulges can be severely attenuated by 50% to 95% depending on disc inclination. We argue that a galaxy's optical appearance can be radically transformed by simply removing the dust, e.g. during cluster infall, with mid-type galaxies becoming earlier, redder, and more luminous. Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1micron to 2.1 micron range, and use this to show that the energy of starlight absorbed by dust (in our model) is in close agreement with the total far-IR emission.

  3. The joint far-infrared-optical luminosity function for spiral galaxies and data for the Abell 400 and Cancer clusters

    International Nuclear Information System (INIS)

    Visual and IRAS data for an optically selected sample of 183 late-type galaxies are compiled in tables and graphs and analyzed in detail to determine the joint FIR-optical luminosity function Psi from the FIR/blue luminosity ratio, r = L(FIR)/L(B). It is found that Psi can be approximated by a function of a single variable psi(r-prime), where r-prime is defined as r times L(B)/L(asterisk) exp -delta, with L(asterisk) a constant and delta = about 0.08. A lognormal curve peaking at r-prime = 0.35 and with dispersion of 0.28 is shown to give a good fit to psi(r-prime). From a lack of galaxies with very low r-prime in the present sample it is inferred that there are few spiral galaxies with low interstellar-dust abundances. Also included are data on the distribution function of r-prime for the more distant clusters Abell 400 and Cancer. 29 refs

  4. A Luminous X-ray Flare From The Nucleus of The Dormant Bulgeless Spiral Galaxy NGC 247

    CERN Document Server

    Feng, Hua; Kaaret, Philip; Tao, Lian; Yamaoka, Kazutaka; Zhang, Shuo; Grisé, Fabien

    2015-01-01

    NGC 247 is a nearby late-type bulgeless spiral galaxy that contains an inactive nucleus. We report a serendipitous discovery of an X-ray flare from the galaxy center with a luminosity up to 2*10^39 erg/s in the 0.3-10 keV band with XMM-Newton. A Chandra observation confirms that the new X-ray source is spatially coincident with the galaxy nucleus. The XMM-Newton data revealed a hard power-law spectrum with a spectral break near 3-4 keV, no pulsations on timescales longer than 150 ms, and a flat power spectrum consistent with Poisson noise from 1 mHz to nearly 10 Hz. Follow-up observations with Swift detected a second flux peak followed by a luminosity drop by factor of almost 20. The spectral and temporal behaviors of the nuclear source are well consistent with the scenario that the flare was due to an outburst of a low-mass X-ray binary that contains a stellar-mass black hole emitting near its Eddington limit at the peak. However, it cannot be ruled out that the sudden brightening in the nucleus was due to a...

  5. Gas-phase oxygen abundances and radial metallicity gradients in the two nearby spiral galaxies NGC7793 and NGC4945

    CERN Document Server

    Stanghellini, Letizia; Casasola, Viviana

    2015-01-01

    Gas-phase abundances in HII regions of two spiral galaxies, NGC7793 and NGC4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8m- Gemini South telescope. We found that NGC7793 has a well-defined gas-phase radial oxygen gradient of -0.321 $\\pm$ 0.112 dex R$_{\\rm 25}^{-1}$ (or -0.054 $\\pm$ 0.019 dex kpc$^{-1}$) in the galactocentric range 0.17$<$R$_{\\rm G}$/R$_{\\rm 25}$ $<$ 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC4945, -0.253 $\\pm$ 0.149 dex R$_{\\rm 25}^{-1}$ (or -0.019 $\\pm$ 0.011 dex kpc$^{-1}$) for 0.04$<$R$_{\\rm G}$/R$_{\\rm 25}$ $<$ 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC7793 and NGC4945 have been selected for this study because they are simil...

  6. Ionized gas characteristics in the cavities of the gas and dust disc of the spiral galaxy NGC 6946

    Science.gov (United States)

    Efremov, Yu. N.; Afanasiev, V. L.; Egorov, O. V.

    2011-07-01

    The parameters of the ionized gas in NGC 6946 (in the [NII] λλ6548, 6583, H α and [SII] λλ6717, 6731 lines) are investigated with the SAO RAS BTA telescope along three positions of the long slit of the SCORPIO focal reducer, passing through a number of large and small cavities of the gaseous disc of the galaxy. These cavities correspond exactly to the cavities in warm dust, visible at 5 - 8µm. We found that everywhere in the direction of NGC 6946 the lines of ionized gas are decomposed into two Gaussians, one of which shows almost constant [SII]/H α and [NII]/H α ratios, as well as an almost constant radial velocity within the measurement errors (about -35… - 50 km/s). This component is in fact the foreground radiation from the diffuse ionized gas of our Galaxy, which is not surprising, given the low (12°) latitude of NGC 6946; a similar component is also present in the emission of neutral hydrogen. The analysis of the component of ionized gas, occurring inNGC 6946, has revealed that it shows signs of shock excitation in the cavities of the gaseous disc of the galaxy. This shock excitation is as well typical for the extraplanar diffuse ionized gas (EDIG), observed in a number of spiral galaxies at their high Z-coordinates. This can most likely be explained by low density of the gas in the NGC 6946 disc (with the usual photoionization) inside the cavities, due to what we see the spectral features of the EDIG gas of NGC 6946, projected onto them, and located outside the plane of the galaxy. In the absence of separation of ionized gas into two components by radial velocities, there is an increasing contribution to the integral line parameters by the EDIG of our Galaxy when the gas density in NGC 6946 decreases, which explains some strange results, obtained in the previous studies. Themorphology of warmdust, visible in the infrared range and HI is almost the same (except for the peripheral parts of the galaxy, where there are no sources of dust heating

  7. A RECIPE TO PROBE ALTERNATIVE THEORIES OF GRAVITATION VIA N-BODY NUMERICAL SIMULATIONS. I. SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    A way to probe alternative theories of gravitation is to study if they could account for the structures of the universe. We therefore modified the well-known Gadget-2 code to probe alternative theories of gravitation through galactic dynamics. As an application, we simulate the evolution of spiral galaxies to probe alternative theories of gravitation whose weak field limits have a Yukawa-like gravitational potential. These simulations show that galactic dynamics can be used to constrain the parameters associated with alternative theories of gravitation. It is worth stressing that the recipe given in this study can be applied to any other alternative theory of gravitation in which the superposition principle is valid.

  8. Discovery of ultra-compact nuclear rings in three spiral galaxies

    CERN Document Server

    Comerón, S; Beckman, J E; Shlosman, I

    2007-01-01

    Ring-shaped morphologies of nuclear star-forming regions within the central 40-200 pc of disk galaxies have been barely resolved so far in three composite Sy2 nuclei, the Sy2 Circinus galaxy and in three non-AGN galaxies. Such morphologies resemble those of the standard 1 kpc-size nuclear rings that lie in the inner Lindblad resonance regions of disk galaxies and, if they have a similar origin, represent recent radial gas inflows tantalisingly close to the central supermassive black holes. We aim to identify the population of such ultra-compact nuclear rings (UCNRs) and study their properties in relation to those of the host galaxies. From archival Hubble Space Telescope UV and Halpha images and from dust structure maps of the circumnuclear regions in nearby galaxies, we analyse the morphology of the star formation and dust, specifically searching for ring structures on the smallest observable scales. In a sample of 38 galaxies studied, we have detected a total of four new UCNRs, 30-130 pc in radius, in three...

  9. Spiral Arms as Cosmic Ray Source Distributions

    CERN Document Server

    Werner, M; Strong, A W; Reimer, O

    2014-01-01

    There is evidence that the distribution of suspected cosmic ray sources are associated with the spiral arm structure of galaxies. It is yet not clearly understood what effect such a cosmic ray source distribution has on the particle transport in our Galaxy. We use the PICARD code to perform high-resolution 3D simulations of electrons and protons in galactic propagation scenarios that include four-arm and two-arm logarithmic spiral cosmic ray source distributions with and without a central bar structure as well as the spiral arm configuration of the NE2001 model for the distribution of free electrons in the Milky Way. Results of these simulation are compared to an axisymmetric radial source distribution. Also, effects on the cosmic ray flux and spectra due to different positions of the Earth relative to the spiral structure are studied. We find that high energy electrons are strongly confined to their sources and the obtained spectra largely depend on the Earth's position relative to the spiral arms. Similar f...

  10. Dynamical study of 2D and 3D barred galaxy models

    CERN Document Server

    Manos, T

    2008-01-01

    We study the dynamics of 2D and 3D barred galaxy analytical models, focusing on the distinction between regular and chaotic orbits with the help of the Smaller ALigment Index (SALI), a very powerful tool for this kind of problems. We present briefly the method and we calculate the fraction of chaotic and regular orbits in several cases. In the 2D model, taking initial conditions on a Poincar\\'{e} $(y,p_y)$ surface of section, we determine the fraction of regular and chaotic orbits. In the 3D model, choosing initial conditions on a cartesian grid in a region of the $(x, z, p_y)$ space, which in coordinate space covers the inner disc, we find how the fraction of regular orbits changes as a function of the Jacobi constant. Finally, we outline that regions near the $(x,y)$ plane are populated mainly by regular orbits. The same is true for regions that lie either near to the galactic center, or at larger relatively distances from it.

  11. Near-infrared constraints on the driving mechanisms for spiral structure

    CERN Document Server

    Seigar, M S; James, P A; Seigar, Marc S.; Chorney, Nicole E.; James, Phil A.

    2003-01-01

    We have imaged a sample of 17 inclined spiral galaxies with measured H$\\alpha$ rotation curves in the K-band, in order to determine the morphology of the old stellar population which dominates the mass in the disc. The K-band images of the galaxies have been used to determine the radial extent of Grand-Design spiral structure and compare this with the turnover radius in their rotation curves, where the rotation curve transforms from solid-body rotation to differential rotation. Thus, if the arms do not extend past this radius, the winding problem is solved. We find in all 17 cases, the arms extend past this radius, with the radius of grand-design spiral structure being a factor of 1.3-9.6 times larger than the rotation curve turnover radius. Of these galaxies, 4 have nearby neighbours and central bars and a further 7 have a central bar. These bars or near neighbours may be the cause of the driving of the spiral potential in the discs of these galaxies. Of the remaining 6 galaxies, 5 show some evidence for a b...

  12. Detection of a ~20 kpc coherent magnetic field in the outskirt of merging spirals: the Antennae galaxies

    CERN Document Server

    Basu, Aritra; Kepley, Amanda A; Robishaw, Timothy; Zweibel, Ellen G; Gallagher, John S

    2016-01-01

    We present a study of the magnetic field properties of NGC 4038/9 (the `Antennae' galaxies), the closest example of a late stage merger of two spiral galaxies. Wideband polarimetric observations were performed using the Karl G. Jansky Very Large Array between 2 and 4 GHz. Rotation measure synthesis and Faraday depolarization analysis was performed to probe the magnetic field strength and structure at spatial resolution of $\\sim1$ kpc. Highly polarized emission from the southern tidal tail is detected with intrinsic fractional polarization close to the theoretical maximum ($0.62\\pm0.18$), estimated by fitting the Faraday depolarization with a volume that is both synchrotron emitting and Faraday rotating containing random magnetic fields. Magnetic fields are well aligned along the tidal tail and the Faraday depths shows large-scale smooth variations preserving its sign. This suggests the field in the plane of the sky to be regular up to $\\sim20$ kpc, which is the largest detected regular field structure on gala...

  13. X-ray sources in the starburst spiral galaxy M83 nuclear region and discrete source population

    CERN Document Server

    Soria, R; Soria, Roberto; Wu, Kinwah

    2002-01-01

    Chandra has resolved the starburst nuclear region of the face-on grand-design spiral M83. Eighty-one point sources are detected above 3.5 sigma in the ACIS S3 image, and 15 of them are within the inner 16-arcsec region of the galaxy. A point source with L_x ~ 3 x 10^(38) erg/s in the 0.3--8.0 keV band is found to coincide with the infra-red nuclear photometric peak, one of the two dynamical nuclei of the galaxy. No point-like sources are resolved (at a 2.5-sigma level) at the centre of symmetry of the outer optical isophote ellipses, suspected to be another dynamical nucleus. About 50% of the total emission in the nuclear region is unresolved; of this, about 70% can be attributed to hot thermal plasma, and the rest is probably due to unresolved point sources (eg, faint X-ray binaries). The azimuthally-averaged radial distribution of the unresolved emission has a King-like profile, with no central cusp. Strong emission lines are seen in the spectrum of the optically thin plasma component. The high abundances o...

  14. X-Ray Properties of the Point Source Population in the Spiral Galaxy NGC 5055 (M63) with Chandra

    CERN Document Server

    Luo, B; Zhang, Z; Wang, Y; Wang, J; Xu, H; Luo, Bing; Chen, Jiyao; Zhang, Zhongli; Wang, Yu; Wang, Jingying; Xu, Haiguang

    2007-01-01

    By analyzing the Chandra ACIS S3 data we studied the X-ray properties of the low-mass and high-mass X-ray binary populations in the nearby spiral galaxy NGC 5055. A total of 43 X-ray point sources were detected within the 2 effective radii, with 31 sources located on the disk and the rest 12 sources in the bulge. The resolved point sources dominate the total X-ray emission of the galaxy by accounting for about 80% of the total counts in 0.3--10 keV. By carrying out the spectral fittings we calculated the 0.3--10.0 keV luminosities of all the detected X-ray point sources and found that they span a wide range from a few 10^{37} erg s^{-1} to over 10^{39} erg s^{-1}. After compensating for the incompleteness at the low luminosity end, we find that the corrected XLF of the bulge population is well fitted with a broken power-law model with a break at 1.57^{+0.21}_{-0.20}\\times 10^{38} erg s^{-1}, while the profile of the disk population's XLF agrees with a single power-law distribution with a slope of 0.93^{+0.07}...

  15. A Wide-field Survey of Two Z~0.5 Galaxy Clusters: Identifying the Physical Processes Responsible for the Observed Transformation of Spirals into S0s

    CERN Document Server

    Moran, Sean M; Treu, Tommaso; Smith, Graham P; Rich, R Michael; Smail, Ian

    2007-01-01

    We present new results from our comprehensive comparative survey of two massive, intermediate redshift galaxy clusters, Cl0024+17 (z=0.39) and MS0451-03 (z=0.54). We identify and study several key classes of `transition objects' whose stellar populations or dynamical states indicate a recent or ongoing change in morphology and star formation rate. For the first time, we have been able to conclusively identify spiral galaxies in the process of transforming into S0 galaxies. This has been accomplished by locating both spirals whose star formation is being quenched as well as their eventual successors, the recently created S0s. Differences between the two clusters in both the timescales and spatial location of this conversion process allow us to evaluate the relative importance of several proposed physical mechanisms that could be responsible for the transformation. Combined with other diagnostics that are sensitive to either ICM-driven galaxy evolution or galaxy-galaxy interactions, we describe a self-consisten...

  16. First results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low Mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    CERN Document Server

    Carlin, Jeffrey L; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F; Brodie, Jean P; Crnojević, Denija; Forbes, Duncan A; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H G; Romanowsky, Aaron J; Strader, Jay

    2016-01-01

    We report the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep imaging with Subaru/Hyper Suprime-Cam. MADCASH J074238+652501-dw lies $\\sim$35 kpc in projection from NGC 2403, a dwarf spiral galaxy at $D$$\\approx$3.2 Mpc. This new dwarf has $M_{g} = -7.4\\pm0.4$ and a half-light radius of $168\\pm70$ pc, at the calculated distance of $3.39\\pm0.41$ Mpc. The color-magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low luminosity dwarfs in the Local Group. The lack of either detected HI gas ($M_{\\rm HI}/L_{V} < 0.69 M_\\odot/L_\\odot$, based on Green Bank Telescope observations) or $GALEX$ NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey, which is conducting a census of the stellar substructure and faint satellites in the halos...

  17. CHANG-ES - VI. Probing Supernova energy deposition in spiral galaxies through multiwavelength relationships

    Science.gov (United States)

    Li, Jiang-Tao; Beck, Rainer; Dettmar, Ralf-Jürgen; Heald, George; Irwin, Judith; Johnson, Megan; Kepley, Amanda A.; Krause, Marita; Murphy, E. J.; Orlando, Elena; Rand, Richard J.; Strong, A. W.; Vargas, Carlos J.; Walterbos, Rene; Wang, Q. Daniel; Wiegert, Theresa

    2016-02-01

    How a galaxy regulates its supernovae (SNe) energy into different interstellar/circumgalactic medium components strongly affects galaxy evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz) continuum observations, we perform statistical analysis comparing multiwavelength properties of the Continuum Haloes in Nearby Galaxies - an EVLA Survey galaxies. The high-quality JVLA data and edge-on orientation enable us for the first time to include the halo into the energy budget for a complete radio-flux-limited sample. We find tight correlations of Lradio with the mid-IR-based star formation rate (SFR). The normalization of our I1.6 GHz/W Hz-1-SFR relation is ˜2-3times of those obtained for face-on galaxies, probably a result of enhanced IR extinction at high inclination. We also find tight correlations between Lradio and the SNe energy injection rate dot{E}_SN(Ia+CC), indicating the energy loss via synchrotron radio continuum accounts for ˜1 of dot{E}_SN, comparable to the energy contained in cosmic ray electrons. The integrated C-to-L-band spectral index is α ˜ 0.5-1.1 for non-active galactic nucleus galaxies, indicating a dominance by the diffuse synchrotron component. The low-scatter Lradio-SFR/L_radio-dot{E}_{SN (Ia+CC)} relationships have superlinear logarithmic slopes at ˜2σ in L band (1.132 ± 0.067/1.175 ± 0.102) while consistent with linear in C band (1.057 ± 0.075/1.100 ± 0.123). The superlinearity could be naturally reproduced with non-calorimeter models for galaxy discs. Using Chandra halo X-ray measurements, we find sublinear LX-Lradio relations. These results indicate that the observed radio halo of a starburst galaxy is close to electron calorimeter, and a galaxy with higher SFR tends to distribute an increased fraction of SNe energy into radio emission (than X-ray).

  18. Gaseous Flows in Galaxies

    OpenAIRE

    Combes, F.

    2007-01-01

    The gas component plays a major role in the dynamics of spiral galaxies, because of its dissipative character, and its ability to exchange angular momentum with stars in the disk. Due to its small velocity dispersion, it triggers gravitational instabilities, and the corresponding non-axisymmetric patterns produce gravity torques, which mediate these angular momentum exchanges. When a srong bar pattern develops with the same pattern speed all over the disk, only gas inside corotation can flow ...

  19. The strong transformation of spiral galaxies infalling into massive clusters at z~0.2

    CERN Document Server

    Cortese, L; Richard, J; Bravo-Alfaro, H; Kneib, J P; Rieke, G; Covone, G; Egami, E; Rigby, J; Czoske, O; Davies, J

    2007-01-01

    We describe two peculiar galaxies falling into the massive galaxy clusters Abell 1689 (z~0.18) and 2667 (z~0.23) respectively. Hubble Space Telescope images show extraordinary trails composed of bright blue knots (-16.5galaxies show similar extended trails of star-forming knots, their recent star formation histories are different. One (~L*) is experiencing a strong burst of star formation, appearing as a rare example of a luminous infrared cluster galaxy. In comparison, the other (~ 0.1 L*) has recently ceased its star formation activity. Our model suggests that the morphologies and star formation in these galaxies have been influenced by the combined action of tidal interaction (likely with the cluster potential) and of ram pressure with the intracluster medium. These results can be used to gain more insights to the origin of S0s, dwarf and ul...

  20. Recalibration of the H$_{-0.5}$ magnitudes of spiral galaxies

    CERN Document Server

    Tormen, G

    1994-01-01

    The H magnitude aperture data published by the Aaronson et al. collaboration over a 10-year period is collected into a homogeneous data set of 1731 observations of 665 galaxies. 96\\% of these galaxies have isophotal diameters and axial ratios determined by the Third Reference Catalogue of Bright Galaxies (de Vaucouleurs et al. 1991), the most self-consistent set of optical data currently available. The precepts governing the optical data in the RC3 are systematically different from those of the Second Reference Catalogue (de Vaucouleurs, de Vaucouleurs and Corwin 1976), which were used by Aaronson et al. for their original analyses of galaxy peculiar motions. This in turn leads to systematic differences in growth curves and fiducial H magnitudes, prompting the present recalibration of the near-infrared Tully Fisher relationship. New optically-normalized H magnitude growth curves are defined for galaxies of types S0 to Im, from which new values of fiducial H magnitudes, H\\rm _{-0.5}^g, are measured for the 665...