scholarly journals Simulating non-axisymmetric flows in disk galaxies

2018 ◽  
Vol 618 ◽  
pp. A106 ◽  
Author(s):  
T. H. Randriamampandry ◽  
N. Deg ◽  
C. Carignan ◽  
L. M. Widrow
Keyword(s):  
Surface Brightness ◽  
Initial Conditions ◽  
Major Axis ◽  
Second Step ◽  
Disk Galaxies ◽  
Distribution Models ◽  
Step Method ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Oriented Parallel

Context. We present a two-step method to simulate and study non-circular motions in strongly barred galaxies. The first step is to constrain the initial parameters using a Bayesian analysis of each galaxy’s azimuthally averaged rotation curve, the 3.6 μm surface brightness, and the gas surface density. The second step is to generate equilibrium models using the GalactICS code and evolve them via GADGET-2. Aims. The bar strengths and mock velocity maps of the resulting snapshots are compared to observations in order to determine the best representation of the galaxy. Methods. We apply our method to the unbarred galaxy NGC 3621 and the barred galaxies NGC 1300 and NGC 1530. NGC 3621 provides a validation of our method of generating initial conditions. NGC 1530 has an intermediate bar orientation that allows for a comparison to DiskFit. Finally NGC 1300 has a bar oriented parallel to the galaxy’s major axis, where other algorithms tend to fail. Results. Our models for NGC 3621 and NGC 1530 are comparable to those obtained using commonly available algorithms. Moreover, we produce one of the first mass distribution models for NGC 1300.

scholarly journals Constraints on Bars in the Local Universe from 5000 SDSS Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 76-76 ◽  
Author(s):  
Fabio D. Barazza ◽  
Shardha Jogee ◽  
Irina Marinova
Keyword(s):  
Large Scale ◽  
Major Axis ◽  
Disk Galaxies ◽  
Semi Major Axis ◽  
Local Universe ◽  
Barred Galaxies ◽  
Sky Survey ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Local Disk

AbstractWe present the first study of bars in the local Universe, based on the Sloan Digitized Sky Survey (SDSS). The large sample of ~5000 local galaxies provides the largest study to date of local bars and minimizes the effect of cosmic variance. The sample galaxies have Mg ≤ −18.5 mag and cover the redshift range 0.01 ≤ z < 0.04. We use a color cut in the color-magnitude diagram and the Sérsic index n to identify disk galaxies. We characterize bars and disks using r-band images and the method of iterative ellipse fits and quantitative criteria developed in Jogee at al. (2004, ApJL, 615, L105). After excluding highly inclined (i>60°) systems our results are: (1) the optical (r-band) fraction of barred galaxies among local disk galaxies is 43% (Figure 1, left panel), which confirms the ubiquity of local bars, in agreement with other optical studies based on smaller samples (e.g. Eskridge et al 2000, AJ, 119, 536, Marinova & Jogee 2006, astro-ph/0608039); (2) the optical bar fraction rises for bluer galaxies, suggesting a relation between bars and star formation (Figure 1, middle panel); (3) preliminary analyzes suggest that the optical bar fraction increases steeply with the galaxy effective radius (reff, Figure 1, right panel); (4) the optical bar fraction at z ~ 0 is ~35% for bright disks (Mg ≤ −19.3 mag) and strong (bar ellipticity >0.4), large-scale (bar semi-major axis >1.5 kpc) bars, which is comparable to the value of ~30 ± 6% reported earlier (Jogee et al 2004) for similar disks and bars at z ~ 0.2 − 1.0.

The Dust Opacity of Spiral Galaxies

1991 ◽  
Vol 9 (1) ◽  
pp. 86-88
Author(s):  
Y. I. Byun ◽  
K. C. Freeman
Keyword(s):  
Radiative Transfer ◽  
Spiral Galaxies ◽  
Transfer Problem ◽  
Major Axis ◽  
Disk Galaxies ◽  
Radiative Transfer Problem ◽  
The Galaxy ◽  
The Asymmetry

AbstractIn order to find the best observable diagnostics for the amount of internal extinction within spiral galaxies, we have constructed models for disk galaxies with immersed dust layers. The radiative transfer problem, including both scattering and pure absorption, has been computed for a range of model galaxies. This reveals a set of superior diagnostics for the opacity. These include the behaviour of the radial colour and luminosity distributions, the amplitude of the asymmetry between the near and far sides of the major axis, and their dependence on the orientation of the galaxy with respect to the observer.

scholarly journals The halo of M 105 and its group environment as traced by planetary nebula populations

2020 ◽  
Vol 642 ◽  
pp. A46
Author(s):  
J. Hartke ◽  
M. Arnaboldi ◽  
O. Gerhard ◽  
L. Coccato ◽  
C. Pulsoni ◽  
...  
Keyword(s):  
Lower Limit ◽  
Density Profile ◽  
Surface Brightness ◽  
Broad Band ◽  
Major Axis ◽  
Asymptotic Giant Branch ◽  
Number Density ◽  
Detection Techniques ◽  
The Galaxy ◽  
Low Mass

Context. M 105 (NGC 3379) is an early-type galaxy in the Leo I group. The Leo I group is the nearest group that contains all main galaxy types and can thus be used as a benchmark to study the properties of the intra-group light (IGL) in low-mass groups. Aims. We present a photometric survey of planetary nebulae (PNe) in the extended halo of the galaxy to characterise its PN populations and investigate the presence of an extended PN population associated with the intra-group light. Methods. We use PNe as discrete stellar tracers of the diffuse light around M 105. These PNe were identified on the basis of their bright [O III]5007 Å emission and the absence of a broad-band continuum using automated detection techniques. We compare the PN number density profile with the galaxy surface-brightness profile decomposed into metallicity components using published photometry of the Hubble Space Telescope in two halo fields. Results. We identify 226 PNe candidates within a limiting magnitude of m5007, lim = 28.1 from our Subaru-SuprimeCam imaging, covering 67.6 kpc (23 effective radii) along the major axis of M 105 and the halos of NGC 3384 and NGC 3398. We find an excess of PNe at large radii compared to the stellar surface brightness profile from broad-band surveys. This excess is related to a variation in the luminosity-specific PN number α with radius. The α-parameter value of the extended halo is more than seven times higher than that of the inner halo. We also measure an increase in the slope of the PN luminosity function at fainter magnitudes with radius. Conclusions. We infer that the radial variation of the PN population properties is due to a diffuse population of metal-poor stars ([M/H] < −1.0) following an exponential profile, in addition to the M 105 halo. The spatial coincidence between the number density profile of these metal-poor stars and the increase in the α-parameter value with radius establishes the missing link between metallicity and the post-asymptotic giant branch phases of stellar evolution. We estimate that the total bolometric luminosity associated with the exponential IGL population is 2.04 × 109 L⊙ as a lower limit. The lower limit on the IGL fraction is thus 3.8%. This work sets the stage for kinematic studies of the IGL in low-mass groups.

scholarly journals Quantifying the Redistribution of Mass in Galactic Disks due to Bars

2010 ◽  
Vol 6 (S277) ◽  
pp. 242-245
Author(s):  
Patricia Sánchez-Blázquez ◽  
Isabel Pérez ◽  
Pierre Ocvirk
Keyword(s):  
Evolutionary Process ◽  
Disk Galaxies ◽  
Galactic Disks ◽  
Chemical Abundance ◽  
Star Forming ◽  
Barred Galaxies ◽  
The Galaxy ◽  
Bulge Region ◽  
Disc Region ◽  
Inside Out

AbstractNumerical simulations have shown that strong gravitational torque by non-axisymmetric components induce evolutionary processes such as redistribution of mass and angular momentum in the galactic disks and consequent change of chemical abundance profiles. If we hope to understand chemical evolution gradients and their evolution we must understand the secular processes and re-arrangement of material by non-axisymmetric components and vice-versa. The most obvious of these aforementioned non-axisymmetric components are bars - at least 2/3 of spiral galaxies host a bar, and possibly all disk galaxies have hosted a bar at some point in their evolution. While observationally it has been found that barred galaxies have shallower gas-phase metallicity gradients than non-barred galaxies, a complementary analysis of the stellar abundance profiles has not yet been undertaken. This is unfortunate because the study of both gas and stars is important in providing a complete picture, as the two components undergo (and suffer from) very different evolutionary process. We present here a pilot study of the gas and stellar metallicity and age distributions in a sample of barred and non-barred galaxies using 2D spectroscopic observations. We found that the majority of the stellar mass in our sample is composed of old (~10 Gyr) stars. This is true in the bulge and the disc region, even beyond two disc scalelengths. In the disc region, a larger fraction of young stars is present in the external parts of the disc compared with the inner disc. The disc growth is, therefore, compatible with a moderate inside-out formation scenario, where the luminosity-weighted age changes from ~10 Gyrs in the centre, to ~4 Gyrs at two disc scalelengths, depending upon the galaxy. However, the presence of substructure, like star forming rings, can produce stellar population trends that are not directly related with the growing of the disc but to the bar potential. In the disc region, the metallicity gradient always decrease with the radius. In the bulge region this is not always true and we find inverse metallicity gradients in several galaxies.

scholarly journals The Fornax Deep Survey with the VST

2019 ◽  
Vol 623 ◽  
pp. A1 ◽  
Author(s):  
E. Iodice ◽  
M. Spavone ◽  
M. Capaccioli ◽  
R. F. Peletier ◽  
G. van de Ven ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Surface Brightness ◽  
Major Axis ◽  
Position Angle ◽  
Early Type ◽  
Semi Major Axis ◽  
Cluster Galaxies ◽  
The Galaxy ◽  
Deep Survey ◽  
Fornax Cluster

Context. This paper is based on the multi-band (ugri) Fornax Deep Survey (FDS) with the VLT Survey Telescope (VST). We study bright early-type galaxies (mB ≤ 15 mag) in the 9 square degrees around the core of the Fornax cluster, which covers the virial radius (Rvir  ∼ 0.7 Mpc). Aims. The main goal of the present work is to provide an analysis of the light distribution for all galaxies out to unprecedented limits (in radius and surface brightness) and to release the main products resulting from this analysis in all FDS bands. We give an initial comprehensive view of the galaxy structure and evolution as a function of the cluster environment. Methods. From the isophote fit, we derived the azimuthally averaged surface brightness profiles, the position angle, and ellipticity profiles as a function of the semi-major axis. In each band, we derived the total magnitudes, effective radii, integrated colours, and stellar mass-to-light ratios. Results. The long integration times, the arcsec-level angular resolution of OmegaCam at VST, and the large covered area of FDS allow us to map the light and colour distributions out to large galactocentric distances (up to about 10−15 Re) and surface brightness levels beyond μr = 27 mag arcsec−2 (μB ≥ 28 mag arcsec−2). Therefore, the new FDS data allow us to explore in great detail the morphology and structure of cluster galaxies out to the region of the stellar halo. The analysis presented in this paper allows us to study how the structure of galaxies and the stellar population content vary with the distance from the cluster centre. In addition to the intra-cluster features detected in previous FDS works, we found a new faint filament between FCC 143 and FCC 147, suggesting an ongoing interaction. Conclusions. The observations suggest that the Fornax cluster is not completely relaxed inside the virial radius. The bulk of the gravitational interactions between galaxies happens in the W-NW core region of the cluster, where most of the bright early-type galaxies are located and where the intra-cluster baryons (diffuse light and globular clusters) are found. We suggest that the W-NW sub-clump of galaxies results from an infalling group onto the cluster, which has modified the structure of the galaxy outskirts (making asymmetric stellar halos) and has produced the intra-cluster baryons (ICL and GCs), concentrated in this region of the cluster.

scholarly journals Characterizing the radial oxygen abundance distribution in disk galaxies

2019 ◽  
Vol 623 ◽  
pp. A7 ◽  
Author(s):  
I. A. Zinchenko ◽  
A. Just ◽  
L. S. Pilyugin ◽  
M. A. Lara-Lopez
Keyword(s):  
Surface Brightness ◽  
Disk Galaxies ◽  
Abundance Distribution ◽  
Oxygen Abundance ◽  
Abundance Gradient ◽  
Central Surface ◽  
The Galaxy ◽  
Axisymmetric Structures ◽  
Local Oxygen ◽  
Optical Radius

Context. The relation between the radial oxygen abundance distribution (gradient) and other parameters of a galaxy such as mass, Hubble type, and a bar strength, remains unclear although a large amount of observational data have been obtained in the past years. Aims. We examine the possible dependence of the radial oxygen abundance distribution on non-axisymmetrical structures (bar/spirals) and other macroscopic parameters such as the mass, the optical radius R25, the color g − r, and the surface brightness of the galaxy. A sample of disk galaxies from the third data release of the Calar Alto Legacy Integral Field Area Survey (CALIFA DR3) is considered. Methods. We adopted the Fourier amplitude A2 of the surface brightness as a quantitative characteristic of the strength of non-axisymmetric structures in a galactic disk, in addition to the commonly used morphologic division for A, AB, and B types based on the Hubble classification. To distinguish changes in local oxygen abundance caused by the non-axisymmetrical structures, the multiparametric mass–metallicity relation was constructed as a function of parameters such as the bar/spiral pattern strength, the disk size, color index g − r in the Sloan Digital Sky Survey (SDSS) bands, and central surface brightness of the disk. The gas-phase oxygen abundance gradient is determined by using the R calibration. Results. We find that there is no significant impact of the non-axisymmetric structures such as a bar and/or spiral patterns on the local oxygen abundance and radial oxygen abundance gradient of disk galaxies. Galaxies with higher mass, however, exhibit flatter oxygen abundance gradients in units of dex/kpc, but this effect is significantly less prominent for the oxygen abundance gradients in units of dex/R25 and almost disappears when the inner parts are avoided (R >  0.25R25). We show that the oxygen abundance in the central part of the galaxy depends neither on the optical radius R25 nor on the color g − r or the surface brightness of the galaxy. Instead, outside the central part of the galaxy, the oxygen abundance increases with g − r value and central surface brightness of the disk.

scholarly journals Scale Length of Disk Galaxies

2010 ◽  
Vol 6 (S277) ◽  
pp. 317-320
Author(s):  
Kambiz Fathi
Keyword(s):  
Galaxy Formation ◽  
Surface Brightness ◽  
Sloan Digital Sky Survey ◽  
Disk Galaxies ◽  
Test Bed ◽  
Massive Galaxies ◽  
Central Surface ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Scale Length

AbstractDisk scale length rd and central surface brightness μ0 for a sample of 29955 bright disk galaxies from the Sloan Digital Sky Survey have been analyzed. Cross correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scale lengths for different types of disk/spiral galaxies and present distributions and typical trends of scale lengths all the SDSS bands with linear relations that indicate the relation that connect scale lengths in one passband to another. We use the volume corrected results in the r-band and revisit the relation between these parameters and the galaxy morphology, and find the average values 〈rd〉 = 3.8 ± 2.1 kpc and 〈μ0〉 = 20.2 ± 0.7 mag arcsec−2. The derived scale lengths presented here are representative for a typical galaxy mass of 1010.8 M⊙, and the RMS dispersion is larger for more massive galaxies. We analyse the rd–μ0 plane and further investigate the Freeman Law and confirm that it indeed defines an upper limit for μ0 in bright disks (rmag < 17.0), and that disks in late type spirals (T ≥ 6) have fainter central surface brightness. Our results are based on a sample of galaxies in the local universe (z < 0.3) that is two orders of magnitudes larger than any sample previously studied, and deliver statistically significant results that provide a comprehensive test bed for future theoretical studies and numerical simulations of galaxy formation and evolution.

scholarly journals Testing a theoretical prediction for bar formation in galaxies with bulges

2020 ◽  
Vol 640 ◽  
pp. A14
Author(s):  
Sandeep Kumar Kataria ◽  
Mousumi Das ◽  
Sudhanshu Barway
Keyword(s):  
Theoretical Prediction ◽  
Observational Data ◽  
Total Force ◽  
Disk Galaxies ◽  
Barred Galaxies ◽  
Wide Range ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Bar Formation ◽  
Scale Length

Earlier studies have shown that massive bulges impede bar formation in disk galaxies. Recent N-body simulations have derived a bar formation criterion that depends on the radial bulge force in a galaxy disk. We use those simulations to show that bars can form only when the force constant FB <  0.13, where FB depends on the ratio of the bulge force to the total force of the galaxy at twice the disk scale length 2Rd. In this article, we test this theoretical prediction using observational data obtained from the literature. Our sample consists of 63 barred galaxies with a wide range of Hubble classes taken from the S4G catalog; for the galaxies that we include, bulge, disk, and bar decomposition has been carried out. We find that 92% of our sample galaxies satisfy the condition FB <  0.13 for bar formation in galaxies and hence agree with the bar formation criterion given by the simulations.

scholarly journals Disk structures in the CGS Survey

2012 ◽  
Vol 10 (H16) ◽  
pp. 358-358
Author(s):  
Zhao-Yu Li ◽  
Luis Ho ◽  
Aaron Barth ◽  
Chien Peng
Keyword(s):  
Surface Brightness ◽  
Spectroscopic Properties ◽  
Disk Galaxies ◽  
Early Type ◽  
Complete Sample ◽  
Fourier Decomposition ◽  
The Galaxy ◽  
Galaxy Environment ◽  
The One

AbstractThe Carnegie-Irvine Galaxy Survey (CGS) is a long term program to investigate the photometric and spectroscopic properties of a statistically complete sample of 605 bright (BT < 12.9 mag), southern (delta < 0 deg) galaxies using the facilities at Las Campanas Observatory. For each galaxy, we have broadband images (BVRI) with good seeing (≈1″) and deep surface brightness (≈27.5 B-band). Using the IRAF task ELLIPSE and the fourier decomposition method, we measured the bar and the lopsidedness properties of disk galaxies in the CGS sample. Our results show that the bar fraction is lower in the early-type galaxies than that in the late-type ones. The (relative) bar length is longer in early-type ones, and strong bars are rare (the one with large ellipticity). We find that the lopsidedness is independent on the galaxy environment, and correlation studies suggest that the lopsided disk may have helped drive gas inward to form stars.

scholarly journals The z = 0.8 precursors of today's bulges

2007 ◽  
Vol 3 (S245) ◽  
pp. 439-442 ◽  
Author(s):  
Marc Balcells ◽  
Lilian Domínguez-Palmero
Keyword(s):  
Surface Brightness ◽  
Disk Galaxies ◽  
Color Structure ◽  
The Galaxy

AbstractWe study the color structure of disk galaxies in the Groth strip at redshifts 0.1 < z < 1.2. Our aim is to test formation models in which bulges form before/after the disk. We find smooth color distributions with gentle outward blueing across the galaxy image: bulges are not distinctly redder than their disks; and bulge colors strongly correlate with global colors. The results suggest a roughly coeval evolution of bulges and disks. About 50% of the nuclei of galaxies with central light excesses above the outer exponential profile hold passively evolving red populations. The remainder 50% are galaxies with central blue colors similar to their disks. They may be bulges in formation, or the central parts of disks with non-exponential surface brightness profiles.

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