- ID:
- ivo://CDS.VizieR/J/ApJ/882/9
- Title:
- SFR & gas-phase metallicity in MaNGA gal.
- Short Name:
- J/ApJ/882/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of gas accretion in galaxy evolution is still a matter of debate. The presence of inflows of metal-poor gas that trigger star formation bursts of low metallicity has been proposed as an explanation for the local anticorrelation between star formation rate (SFR) and gas-phase metallicity (Z_g_) found in the literature. In the present study, we show how the anticorrelation is also present as part of a diversified range of behaviors for a sample of more than 700 nearby spiral galaxies from the SDSS-IV MaNGA survey. We have characterized the local relation between SFR and Z_g_ after subtracting the azimuthally averaged radial profiles of both quantities. Of the analyzed galaxies, 60% display an SFR-Z_g_ anticorrelation, with the remaining 40% showing no correlation (19%) or positive correlation (21%). Applying a random forest machine-learning algorithm, we find that the slope of the correlation is mainly determined by the average gas-phase metallicity of the galaxy. Galaxy mass, g-r colors, stellar age, and mass density seem to play a less significant role. This result is supported by the performed second-order polynomial regression analysis. Thus, the local SFR-Z_g_ slope varies with the average metallicity, with the more metal-poor galaxies presenting the lowest slopes (i.e., the strongest SFR-Z_g_ anticorrelations), and reversing the relation for more metal-rich systems. Our results suggest that external gas accretion fuels star formation in metal-poor galaxies, whereas in metal-rich systems, the gas comes from previous star formation episodes.
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- 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.
- 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/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/MNRAS/345/1
- Title:
- Shape of CL 1358+62 galaxies
- Short Name:
- J/MNRAS/345/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of early-type galaxies, both in the local Universe and in clusters at medium redshifts, suggest that these galaxies often contain discs or disc-like structures. Using the results of Kelson et al. (2000ApJ...531..137K) for the incidence of disc-components among the galaxies in the redshift z=0.33 cluster CL 1358+62, we investigate the effect of disc structures on the lensing properties of early-type galaxies. Statistical properties, like magnification cross-sections and the expected number of quad (four-image) lens systems, are not affected greatly by the inclusion of discs that contain less than ~10 per cent of the total stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/153/57
- Title:
- Shape parameters for 154 Galactic open clusters
- Short Name:
- J/AJ/153/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Galactic characteristics of 154 open clusters using the stellar statistics method with data from the WEBDA database. We find that all clusters in our sample are elongated in shape, which indicates that the spherical clusters are stretched out to be ellipsoid as a function of age (log(age/year)=6.64{--}9.7). By dividing a cluster into a central core and an outer part, we have computed the apparent ellipticities of these two parts respectively. The scale relations between ellipticities and age indicate that the outer parts of open clusters become more elliptical while the central cores remain circular. We suppose that the outer parts become more elliptical because they are more subjected to the external forces, e.g., Galactic differential rotation, while the central cores form a circular shape under the domination of stellar dynamics. We have also performed an analysis of the crucial influence of cluster mass and location on its shape.
- ID:
- ivo://CDS.VizieR/J/A+A/495/807
- Title:
- Shape parameters for 650 open clusters
- Short Name:
- J/A+A/495/807
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ellipticities have been determined for only a few tens of open clusters. We derive the observed and modelled shape parameters (apparent ellipticity and orientation of the ellipse) of 650 Galactic open clusters identified in the ASCC-2.5 catalogue (Kharchenko, 2001, Cat. I/280).
- ID:
- ivo://CDS.VizieR/J/A+A/585/A84
- Title:
- Shape parameters of lensing galaxies
- Short Name:
- J/A+A/585/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity profiles of galaxies acting as strong gravitational lenses can be tricky to study. Indeed, strong gravitational lensing images display several lensed components, both point-like and diffuse, around the lensing galaxy. Those objects limit the study of the galaxy luminosity to its inner parts. Therefore, the usual fitting methods perform rather badly on such images. Previous studies of strong lenses luminosity profiles using software such as like GALFIT or IMFITFITS and various PSF-determining methods have resulted in somewhat discrepant results. The present work aims at investigating the causes of those discrepancies, as well as at designing more robust techniques for studying the morphology of early-type lensing galaxies with the ability to subtract a lensed signal from their luminosity profiles. The morphology of early-type lensing galaxies with the ability to subtract a lensed signal from their luminosity profiles. Methods. We design a new method to independently measure each shape parameter, namely, the position angle, ellipticity, and half- light radius of the galaxy. Our half-light radius measurement method is based on an innovative scheme for computing isophotes that is well suited to measuring the morphological properties of gravitational lensing galaxies. Its robustness regarding various specific aspects of gravitational lensing image processing is analysed and tested against GALFIT. It is then applied to a sample of systems from the CASTLES database.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1490
- Title:
- Shapes of BCGs in nearby clusters shapes
- Short Name:
- J/MNRAS/404/1490
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the apparent axial ratio distributions of the brightest cluster galaxies (BCGs) and normal ellipticals (Es) in our sample of 75 galaxy clusters from the WIde-field Nearby Galaxy-cluster Survey (WINGS). Most BCGs in our clusters (69 per cent) are classified as cD galaxies. The sample of cDs has been completed by 14 additional cDs (non-BCGs) we found in our clusters. We deproject the apparent axial ratio distributions of Es, BCGs and cDs using a bivariate version of the Lucy rectification algorithm, whose results are supported by an independent Monte Carlo technique. Finally, we compare the intrinsic shape distribution of BCGs to the corresponding shape distribution of the central part of cluster-sized dark matter haloes extracted from the GIF2 Lambda cold dark matter ({LAMBDA}CDM) N-body simulations (Gao et al., 2004MNRAS.355..819G).
