- ID:
- ivo://CDS.VizieR/J/A+A/592/A108
- Title:
- RXJ1257.2+4738 morphological properties
- Short Name:
- J/A+A/592/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studying the evolution of the morphological distribution of galaxies in different environments can provide important information about the effects of the environment and the physical mechanisms responsible for the morphological transformations. As part of a complete analysis of the young cluster RXJ 1257+4738 at z~0.9, in this work we study the morphological properties of its galaxies. We used non-parametric methods of morphological classification, as implemented in the galSVM code. The classification with the applied method was possible even using ground-based observations, as the r'-band imaging from OSIRIS/GTC. We defined very conservative probability limits, taking into account the probability errors, to obtain a trustworthy classification. In this way we were able to classify ~30% of all cluster members and to separate between late-type (LT) and early-type (ET) galaxies. Additionally, when analysing the colour-magnitude diagram, we observed a significant population of blue ET galaxies among the classified ones. We discussed possible explanations for finding this population. Moreover, we studied different physical properties of LT, ET, and blue ET galaxies. They turn out to be comparable, with the exception of the stellar mass that shows that the red ET population is more massive. We also analysed the morphology-density and morphology-radius relations observing that, only when considering the morphological separation between ET and LT galaxies, a mild classical behaviour is obtained. RXJ 1257+4738 is a young galaxy cluster, showing a clumpy structure, which is still in the process of formation, and which could explain the lack of some of the standard morphological relations. This makes this cluster a very attractive case for obtaining higher resolution data and for studying the morphological properties of the entire cluster in more detail and their relation to the environment.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/123
- Title:
- SAMI Galaxy Survey asymmetries
- Short Name:
- J/MNRAS/465/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the properties of kinematically disturbed galaxies in the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey using a quantitative criterion, based on kinemetry (Krajnovic et al., 2011MNRAS.414.2923K). The approach, similar to the application of kinemetry by Shapiro et al., uses ionized gas kinematics, probed by H{alpha} emission. By this method, 23+/-7 per cent of our 360-galaxy sub-sample of the SAMI Galaxy Survey are kinematically asymmetric. Visual classifications agree with our kinemetric results for 90 per cent of asymmetric and 95 per cent of normal galaxies. We find that stellar mass and kinematic asymmetry are inversely correlated and that kinematic asymmetry is both more frequent and stronger in low-mass galaxies. This builds on previous studies that found high fractions of kinematic asymmetry in low-mass galaxies using a variety of different methods. Concentration of star formation and kinematic disturbance are found to be correlated, confirming results found in previous work. This effect is stronger for high-mass galaxies (log(M*)>10) and indicates that kinematic disturbance is linked to centrally concentrated star formation. Comparison of the inner (within 0.5Re) and outer H{alpha} equivalent widths of asymmetric and normal galaxies shows a small but significant increase in inner equivalent width for asymmetric galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/60
- Title:
- SAMI Galaxy Survey: early-type gal. in A119 & A168
- Short Name:
- J/ApJ/875/60
- Date:
- 08 Mar 2022 13:03:14
- Publisher:
- CDS
- Description:
- We investigate the kinematic alignments of luminous early-type galaxies (M_r_<=-19.5mag) in A119 and A168 using the kinematic position angles (PA_kin_) from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) survey data, motivated by the implication of the galaxy spin alignment in a cosmological context. To increase the size of our sample for statistical significance, we also use the photometric position angles (PA_phot_) for galaxies that have not been observed by SAMI, if their ellipticities are higher than 0.15. Our luminous early-type galaxies tend to prefer the specific position angles in both clusters, confirming the results of Kim+ (2018ApJ...860L...3K), who recently found the kinematic alignment of early-type galaxies in the Virgo cluster based on the ATLAS3D integral-field spectroscopic data. This alignment signal is more prominent for galaxies in the projected phase-space regions dominated by infalling populations. Furthermore, the alignment angles are closely related to the directions of the filamentary structures around clusters. The results lead us to conclude that many cluster early-type galaxies are likely to be accreted along filaments while maintaining their spin axes, which are predetermined before cluster infall.
- ID:
- ivo://CDS.VizieR/J/MNRAS/456/1299
- Title:
- SAMI Galaxy Survey: gas streaming
- Short Name:
- J/MNRAS/456/1299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric fits out to r~2re. For 12/14 with measured HI profiles, ionized gas and HI maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial light profile as nested, very flattened mass homeoids viewed as a Sersic form. Fitting broad-band spectral energy distributions to Sloan Digital Sky Survey images gave median stellar mass/light 1.7 assuming a Kroupa initial mass function (IMF) versus 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM distributed like starlight across the SAMI aperture that came to dominate motions as the starlight CSCs declined rapidly. The rest had mass distributed differently from light. Subtracting fits of Sersic radial profiles to 13 VIKING Z-band images revealed residual weak bars. Near the bar major axis, we assessed m=2 streaming velocities, and found deviations usually <30km/s from the CSC; three showed no deviation. Thus, asymmetries rarely influenced the CSC despite colocated shock-indicating, emission-line flux ratios in more than 2/3 of our sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/3965
- Title:
- SAMI Galaxy Survey. Gas surface densities
- Short Name:
- J/MNRAS/468/3965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2_) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2_, but CO is much less abundant and the conversion from CO intensity to H_2_ mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas ({Sigma}_gas_) using optical spectroscopy. We utilize the spatially resolved H{alpha} maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of {Sigma}_gas_ by inverting the multi-freefall star formation relation, which connects the star formation rate surface density ({Sigma}_SFR_) with {Sigma}_gas_ and the turbulent Mach number (M). Based on the measured range of {Sigma}_SFR_=0.005-1.5M_{sun}_/yr/kpc^2^ and M=18-130, we predict {Sigma}_gas_=7-200M_{sun}_/pc^2^ in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured {Sigma}_gas_ obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'star-forming' (219) or 'composite/AGN/shock' (41), and find that in 'composite/AGN/shock' galaxies the average {Sigma}_SFR_, M and {Sigma}_gas_ are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of {Sigma}_gas_ with those obtained by inverting the Kennicutt-Schmidt relation and find that our new method is a factor of 2 more accurate in predicting {Sigma}_gas_, with an average deviation of 32 per cent from the actual {Sigma}_gas_.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/104
- Title:
- SAMI Galaxy Survey: rotators classification
- Short Name:
- J/ApJ/835/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h_3_ (~skewness) and h_4_ (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter ({lambda}R_e_) and ellipticity ({epsilon}_e_) are used to separate fast and slow rotators; there exists a good correspondence to regular and non-regular rotators, respectively, as also seen in earlier studies. We confirm that regular rotators show a strong h_3_ versus V/{sigma} anti-correlation, whereas quasi-regular and non-regular rotators show a more vertical relation in h_3_ and V/{sigma}. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h_3_ versus V/{sigma} signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow rotators, whereas Classes 2-5 correspond to fast rotators. We find that galaxies with similar {lambda}R_e_-{epsilon}_e_ values can show distinctly different h_3_-V/{sigma} signatures. Class 5 objects are previously unidentified fast rotators that show a weak h_3_ versus V/{sigma} anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h_3_ versus V/{sigma} as evidence for disks in most fast rotators, suggesting a dearth of gas-poor mergers among fast rotators.
567. SAMI Pilot Survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/2050
- Title:
- SAMI Pilot Survey
- Short Name:
- J/MNRAS/454/2050
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the SAMI Pilot Survey, consisting of integral field spectroscopy of 106 galaxies across three galaxy clusters, Abell 85, Abell 168 and Abell 2399. The galaxies were selected by absolute magnitude to have Mr<-20.25mag. The survey, using the Sydney-AAO Multi-object Integral field spectrograph (SAMI), comprises observations of galaxies of all morphological types with 75 per cent of the sample being early-type galaxies (ETGs) and 25 per cent being late-type galaxies (LTGs). Stellar velocity and velocity dispersion maps are derived for all 106 galaxies in the sample. The {lambda}_R_ parameter, a proxy for the specific stellar angular momentum, is calculated for each galaxy in the sample. We find a trend between {lambda}_R_ and galaxy concentration such that LTGs are less concentrated higher angular momentum systems, with the fast-rotating ETGs (FRs) more concentrated and lower in angular momentum. This suggests that some dynamical processes are involved in transforming LTGs to FRs, though a significant overlap between the {lambda}_R_ distributions of these classes of galaxies implies that this is just one piece of a more complicated picture. We measure the kinematic misalignment angle, {Psi}, for the ETGs in the sample, to probe the intrinsic shapes of the galaxies. We find the majority of FRs (83 per cent) to be aligned, consistent with them being oblate spheroids (i.e. discs). The slow rotating ETGs (SRs), on the other hand, are significantly more likely to show kinematic misalignment (only 38 per cent are aligned). This confirms previous results that SRs are likely to be mildly triaxial systems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/2690
- Title:
- Sample of Compact Group (CG) galaxies
- Short Name:
- J/MNRAS/423/2690
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a sample of 75863 star-forming galaxies with robust metallicity and star formation rate (SFR) measurements from the Sloan Digital Sky Survey Data Release 7, from which we select a clean sample of compact group (CG) galaxies. The CGs are defined to be close configurations of at least four galaxies that are otherwise apparently isolated. Our selection results in a sample of 112 spectroscopically identified CG galaxies, which can be further divided into groups that are either embedded within a larger structure, such as a cluster or large group, or truly isolated systems. The CGs then serve as a probe into the influence of large-scale environment on a galaxy's evolution, while keeping the local density fixed at high values. W
- ID:
- ivo://CDS.VizieR/J/A+A/623/A122
- Title:
- Sample of MaNGA galaxies properties
- Short Name:
- J/A+A/623/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)_0_, the abundance at the optical radius (O/H)_R25_, and the abundance gradient with rotation velocity V_rot_ were examined for galaxies with rotation velocities from 90km/s to 350km/s. We find that each relation shows a break at V_rot_^*^~200km/s. The central (O/H)_0_ abundance increases with rising V_rot_ and the slope of the (O/H)_0_-V_rot_ relation is steeper for galaxies with V_rot_<=V_rot_^*^. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with V_rot_>=V_rot_^*^. The abundance gradient expressed in dex/R_25_ is roughly constant for galaxies with V_rot_<=V_rot_^*^, flattens towards V_rot_^*^, and then again is roughly constant for galaxies with V_rot_>=V_rot_^*^. The change of the gradient expressed in terms of dex/h_d_ (where h_d_ is the disc scale length), in terms of dex/R_e,d_ (where R_e,d_ is the disc effective radius), and in terms of dex/R_e,g_ (where R_e,g_ is the galaxy effective radius) with rotation velocity is similar to that for gradient in dex/R_25_. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered.
- ID:
- ivo://CDS.VizieR/J/MNRAS/467/2127
- Title:
- 4 samples of disc galaxies
- Short Name:
- J/MNRAS/467/2127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the influence of environment on the structure of disc galaxies, using IMFIT to measure the g- and r-band structural parameters of the surface-brightness profiles for ~700 low-redshift (z<0.063) cluster and field disc galaxies with intermediate stellar mass (0.8x10^10^M_{sun}_<M*<4x10^10^M_{sun}_) from the Sloan Digital Sky Survey, DR7. Based on this measurement, we assign each galaxy to a surface-brightness profile type (Type I = single-exponential, Type II = truncated, Type III = antitruncated). In addition, we measure (g-r) rest frame colour for disc regions separated by the break radius. Cluster disc galaxies (at the same stellar mass) have redder (g-r) colour by ~0.2 mag than field galaxies. This reddening is slightly more pronounced outside the break radius. Cluster disc galaxies also show larger global Sersic-indices and are more compact than field discs, both by ~15 per cent. This change is connected to a flattening of the (outer) surface-brightness profile of Type I and - more significantly - of Type III galaxies by ~8 per cent and ~16 per cent, respectively, in the cluster environment compared to the field. We find fractions of Type I, Type II and Type III of (6+/-2) per cent, (66+/-4) per cent and (29+/-4) per cent in the field and (15_-4_^+7^) per cent, (56+/-7) per cent and (29+/-7) per cent in the cluster environment, respectively. We suggest that the larger abundance of Type I galaxies in clusters (matched by a corresponding decrease in the Type II fraction) could be the signature of a transition between Type II and Type I galaxies produced/enhanced by environment-driven mechanisms.
