- ID:
- ivo://CDS.VizieR/J/MNRAS/474/1307
- Title:
- S0 galaxies morpho-kinematic properties
- Short Name:
- J/MNRAS/474/1307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 28 S0 galaxies extracted from the integral field spectroscopic (IFS) survey Calar Alto Legacy Integral Field Area. We combine an accurate two-dimensional (2D) multicomponent photometric decomposition with the IFS kinematic properties of their bulges to understand their formation scenario. Our final sample is representative of S0s with high stellar masses (M*/M_{sun}_>10^10^). They lay mainly on the red sequence and live in relatively isolated environments similar to that of the field and loose groups. We use our 2D photometric decomposition to define the size and photometric properties of the bulges, as well as their location within the galaxies. We perform mock spectroscopic simulations mimicking our observed galaxies to quantify the impact of the underlying disc on our bulge kinematic measurements ({nu} and v/{lambda}). We compare our bulge corrected kinematic measurements with the results from Schwarzschild dynamical modelling. The good agreement confirms the robustness of our results and allows us to use bulge deprojected values of {lambda} and v/{sigma}. We find that the photometric (n and B/T) and kinematic (v/{sigma} and {lambda}) properties of our field S0 bulges are not correlated. We demonstrate that this morpho-kinematic decoupling is intrinsic to the bulges and it is not due to projection effects. We conclude that photometric diagnostics to separate different types of bulges (disc-like versus classical) might not be useful for S0 galaxies. The morpho-kinematics properties of S0 bulges derived in this paper suggest that they are mainly formed by dissipational processes happening at high redshift, but dedicated high-resolution simulations are necessary to better identify their origin.
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- ID:
- ivo://CDS.VizieR/J/A+A/596/A84
- Title:
- S4G disk galaxies stellar mass distribution
- Short Name:
- J/A+A/596/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Models of galaxy formation in a cosmological framework require observational constraints to be tested against, such as the average stellar density profiles (and their dispersion) as a function of fundamental galaxy properties (e.g. the total stellar mass). Simulation models predict that the torques produced by stellar bars efficiently redistribute the stellar and gaseous material inside the disk, pushing it outwards or inwards depending on whether it is beyond or inside the bar corotation resonance radius, respectively. Bars themselves are expected to evolve, getting longer and narrower as they trap particles from the disk and slow down their rotation speed. We use 3.6um photometry from the Spitzer Survey of Stellar Structure in Galaxies (S4G) to trace the stellar distribution in nearby disk galaxies (z~~0) with total stellar masses 10^8.5^<=M*/M_{sun}_<=10^11^ and mid IR Hubble types -3<=T<=10. We characterize the stellar density profiles ({SIGMA}*), the stellar contribution to the rotation curves (V3.6um) and the m=2 Fourier amplitudes (A2) as a function of M* and T. We also describe the typical shapes and strengths of stellar bars in the S4G sample and link their properties to the total stellar mass and morphology of their host galaxy. For 1154 S4G galaxies with disk inclinations lower than 65{deg}, we perform a Fourier decomposition and rescale their images to a common frame determined by the size in physical units, by their disk scalelength, and for 748 barred galaxies 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* and T. Based on the radial force profiles of individual galaxies we calculate the mean stellar contribution to the circular velocity. We also calculate average A2 profiles, where the radius is normalized to R25.5. Furthermore, we infer the gravitational potentials from the synthetic bars to obtain the tangential-to-radial force ratio (QT) and A2 profiles in the different bins. We also apply ellipse fitting to quantitatively characterize the shape of the bar stacks. For M*>=10^9^M_{sun}_, we find a significant difference in the stellar density profiles of barred and non-barred systems: (i) disks in barred galaxies show larger scalelengths (hR) and fainter extrapolated central surface brightnesses ({SIGMA}0), (ii) the mean surface brightness profiles ({SIGMA}*) of barred and non-barred galaxies intersect each other slightly beyond the mean bar length, most likely at the bar corotation, and (iii) the central mass concentration of barred galaxies is larger (by almost a factor 2 when T<=5) than in their non-barred counterparts. The averaged {SIGMA}* profiles follow an exponential slope down to at least ~10M_{sun}_/pc^2^, which is the typical depth beyond which the sample coverage in the radial direction starts to drop. Central mass concentrations in massive systems (>=10^10^M_{sun}_) are substantially larger than in fainter galaxies, and their prominence scales with T. This segregation also manifests in the inner slope of the mean stellar component of the circular velocity: lenticular (S0) galaxies present the most sharply rising V3.6um . Based on the analysis of bar stacks, we show that early- and intermediate-type spirals (0<=T<5) have intrinsically narrower bars compared to later types and S0s, whose bars are oval-shaped. We show a clear agreement between galaxy family and quantitative estimates of bar strength. In early- and intermediate-type spirals, A2 is larger within and beyond the typical bar region among barred galaxies, compared to the non-barred subsample. Strongly barred systems also tend to have larger A2 amplitudes at all radii than their weakly barred counterparts. Using near-IR wavelengths (S4G 3.6um), we provide observational constraints for galaxy formation models to be checked against. In particular, we calculate the mean stellar density profiles, and the disk(+bulge) component of the rotation curve (and their dispersion) in bins of M* and T. We find evidence for bar-induced secular evolution of disk galaxies, in terms of disk spreading and enhanced central mass concentration. We also obtain average bars (2-D), and we show that bars hosted by early-type galaxies are more centrally concentrated and have larger density amplitudes than their late-type counterparts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/5689
- Title:
- S4G galaxies disk/bar decomposition
- Short Name:
- J/MNRAS/478/5689
- Date:
- 08 Feb 2022 00:30:06
- Publisher:
- CDS
- Description:
- We present photometric models of 532 disc galaxies in 3.6um images from the Spitzer Survey of Stellar Structure in Galaxies (S^4^G) using the non-parametric DISKFIT algorithm. We first test DISKFIT's performance on 400 synthetic S^4^G-like galaxy images. DISKFIT is unreliable in the bulge region, but accurately disentangles exponential discs from Ferrers bars farther out as long as their position angles differ by more than 5{deg}. We then proceed to model the S^4^G galaxies, successfully fitting 489 of them using an automated approach for initializing DISKFIT, optimizing the model and deriving uncertainties using a bootstrap-resampling technique. The resulting component geometries and surface brightness profiles are compared to those derived by Salo et al. using the parametric model GALFIT. We find generally good agreement between the models, but discrepancies between best-fitting values for individual systems are often significant: the choice of algorithm clearly impacts the inferred disc and bar structure. In particular, we find that DISKFIT typically assigns more light to the bar and less light to the disc relative to the Ferrers and exponential profiles derived using GALFIT in the bar region. Given DISKFIT's reliability at disentangling these components in our synthetic images, we conclude that the surface brightness distributions of barred S^4^G galaxies are not well-represented by these functional forms. The results presented here underscore the importance of validating photometric decomposition algorithms before applying them to real data and the utility of DISKFIT's non-parametric approach at measuring the structure of discs and bars in nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/32
- Title:
- S4G galaxy morphologies in the CVRHS system
- Short Name:
- J/ApJS/217/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Survey of Stellar Structure in Galaxies (S^4^G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S^4^G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de Vaucouleurs morphology, modified to include recognition of other features such as inner, outer, and nuclear lenses, nuclear rings, bars, and disks, spheroidal galaxies, X patterns and box/peanut structures, OLR subclass outer rings and pseudorings, bar ansae and barlenses, parallel sequence late-types, thick disks, and embedded disks in 3D early-type systems. We show that our CVRHS classifications are internally consistent, and that nearly half of the S^4^G sample consists of extreme late-type systems (mostly bulgeless, pure disk galaxies) in the range Scd-Im. The most common family classification for mid-IR types S0/a to Sc is SA while that for types Scd to Sm is SB. The bars in these two type domains are very different in mid-IR structure and morphology. This paper examines the bar, ring, and type classification fractions in the sample, and also includes several montages of images highlighting the various kinds of "stellar structures" seen in mid-IR galaxy morphology.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/7
- Title:
- SG1120-1202 members HST imaging & 24um fluxes
- Short Name:
- J/ApJ/836/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Hubble Space Telescope to obtain WFC3/F390W imaging of the supergroup SG1120-1202 at z=0.37, mapping the UV emission of 138 spectroscopically confirmed members. We measure total (F390W-F814W) colors and visually classify the UV morphology of individual galaxies as "clumpy" or "smooth." Approximately 30% of the members have pockets of UV emission (clumpy) and we identify for the first time in the group environment galaxies with UV morphologies similar to the "jellyfish" galaxies observed in massive clusters. We stack the clumpy UV members and measure a shallow internal color gradient, which indicates that unobscured star formation is occurring throughout these galaxies. We also stack the four galaxy groups and measure a strong trend of decreasing UV emission with decreasing projected group distance (R_proj_). We find that the strong correlation between decreasing UV emission and increasing stellar mass can fully account for the observed trend in (F390W-F814W)-R_proj_, i.e., mass-quenching is the dominant mechanism for extinguishing UV emission in group galaxies. Our extensive multi-wavelength analysis of SG1120-1202 indicates that stellar mass is the primary predictor of UV emission, but that the increasing fraction of massive (red/smooth) galaxies at R_proj_<~2R_200_ and existence of jellyfish candidates is due to the group environment.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/4
- Title:
- S4G pipeline 4: multi-component decompositions
- Short Name:
- J/ApJS/219/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Survey of Stellar Structure in Galaxies (S^4^G) is a deep 3.6 and 4.5{mu}m imaging survey of 2352 nearby (<40Mpc) galaxies. We describe the S^4^G data analysis pipeline 4, which is dedicated to two-dimensional structural surface brightness decompositions of 3.6{mu}m images, using GALFIT3.0. Besides automatic 1-component Sersic fits, and 2-component Sersic bulge + exponential disk fits, we present human-supervised multi-component decompositions, which include, when judged appropriate, a central point source, bulge, disk, and bar components. Comparison of the fitted parameters indicates that multi-component models are needed to obtain reliable estimates for the bulge Sersic index and bulge-to-total light ratio (B/T), confirming earlier results. Here, we describe the preparations of input data done for decompositions, give examples of our decomposition strategy, and describe the data products released via IRSA and via our web page (www.oulu.fi/astronomy/S4G_PIPELINE4/MAIN). These products include all the input data and decomposition files in electronic form, making it easy to extend the decompositions to suit specific science purposes. We also provide our IDL-based visualization tools (GALFIDL) developed for displaying/running GALFIT-decompositions, as well as our mask editing procedure (MASK_EDIT) used in data preparation. A detailed analysis of the bulge, disk, and bar parameters derived from multi-component decompositions will be published separately.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A46
- Title:
- Sgr dSph nucleus stars chemical abundances
- Short Name:
- J/A+A/605/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Iron, Magnesium, Calcium, and Titanium abundances for 235 stars in the central region of the Sagittarius dwarf spheroidal galaxy (within 9.0'~=70pc from the center) from medium-resolution Keck/DEIMOS spectra. All the considered stars belong to the massive globular cluster M 54 or to the central nucleus of the galaxy (Sgr,N). In particular we provide abundances for 109 stars with [Fe/H]>=-1.0, more than doubling the available sample of spectroscopic metallicity and {alpha}-elements abundance estimates for Sgr dSph stars in this metallicity regime. We find for the first time a metallicity gradient in the Sgr,N population, whose peak iron abundance goes from [Fe/H]=-0.38 for R<=2.5' to [Fe/H]=-0.57 for 5.0<R<=9.0 arcmin. On the other hand the trends of [Mg/Fe], [Ca/Fe], and [Ti/Fe] with [Fe/H] are the same over the entire region explored by our study. We reproduce the observed chemical patterns of the Sagittarius dwarf spheroidal as a whole with a chemical evolution model implying a high mass progenitor (M_DM_=6x10^10^M_{sun}_) and a significant event of mass-stripping occurred a few Gyr ago, presumably starting at the first peri-Galactic passage after infall.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2647
- Title:
- Sgr dSph stars spectral classification
- Short Name:
- J/MNRAS/427/2647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectra of 1142 colour-selected stars in the direction of the Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy, of which 1058 were taken with VLT/FLAMES multi-object spectrograph and 84 were taken with the SAAO Radcliffe 1.9-m telescope grating spectrograph. Spectroscopic membership is confirmed (at >99 per cent confidence) for 592 stars on the basis of their radial velocity, and spectral types are given. Very slow rotation is marginally detected around the galaxy's major axis. We identify five S stars and 23 carbon stars, of which all but four carbon stars are newly determined and all but one (PQ Sgr) are likely Sgr dSph members. We examine the onset of carbon richness in this metal-poor galaxy in the context of stellar models. We compare the stellar death rate (one star per 1000-1700yr) with the known planetary nebula dynamical ages and find that the bulk population produce the observed (carbon-rich) planetary nebulae. We compute average lifetimes of S and carbon stars as 60-250 and 130-500kyr, compared to a total thermal-pulsing asymptotic giant branch lifetime of 530-1330kyr. We conclude by discussing the return of carbon-rich material to the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A62
- Title:
- Sgr dSph VIMOS photometry and radial velocities
- Short Name:
- J/A+A/513/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) provides us with a unique possibility of studying a dwarf galaxy merging event while still in progress. Moving along a short-period, quasi-polar orbit in the Milky Way Halo, Sgr dSph is being tidally dispersed along a huge stellar stream. Due to its low distance (25kpc), the main body of Sgr dSph covers a vast area in the sky (roughly 15x7degrees). Available photometric and spectroscopic studies have concentrated either on the central part of the galaxy or on the stellar stream, but the overwhelming majority of the galaxy body has never been probed. The aim of the present study is twofold. On the one hand, to produce color magnitude diagrams across the extension of Sgr dSph to study its stellar populations, searching for age and/or composition gradients (or lack thereof). On the other hand, to derive spectroscopic low-resolution radial velocities for a subsample of stars to determine membership to Sgr dSph for the purpose of high resolution spectroscopic follow-up.
- ID:
- ivo://CDS.VizieR/VII/196
- Title:
- Shakhbazian compact groups of galaxies
- Short Name:
- VII/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The largest survey of compact galaxy groups was published by Shakhbazian et al. (see cat. <VII/89>). This catalogue provides accurate positions of individual galaxies in the groups; photometrical properties of the Southern sky (delta not greater than +2{deg}30') are evaluated on the basis of the COSMOS/UKST catalog of the Southern sky. The catalogue contains 373 groups; this number differs from the number in Shakhbazian's list (377 groups) by the following: => No data for groups 001 (there were already published data by other authors), 206 (could not be re-identified) 241 (could not be re-identified) 252 (is identical with 214), 301 (could not be re-identified) 353 (could not be re-identified) => Group 328 was published twice (in North and South) => Group 340 was divided in two parts (340 and 340a), according to Bettoni and Fasano ([BF95]=1995AJ....109...32B)
