- ID:
- ivo://CDS.VizieR/J/A+A/649/A93
- Title:
- Stellar populations of NGC 3311
- Short Name:
- J/A+A/649/A93
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Massive early-type galaxies are believed to be the end result of an extended mass accretion history. The stars formed in situ, very early during the initial phase of the assembly, might have originated from an extremely intense and rapid burst of star formation. These stars may still be found within the cores of such galaxies at z=0, depending on their accretion and merger histories. We wish to investigate the presence of a surviving high-z compact progenitor component in the brightest galaxy of the Hydra~I cluster, NGC~3311, by mapping its 2D kinematics and stellar population out to 2 effective radii. Our goal is to understand the formation of its several structural components and trace their mass assembly back in time. We combine MUSE observations, a customized and extended version of the state-of-the-art EMILES single stellar population models, and a newly developed parametric fully Bayesian framework to model the observed spectra using full-spectrum fitting. We present 2D maps, as well as radial profiles, of the stellar velocity dispersion, age, total metallicity, {alpha}-element, sodium abundance ([Na/Fe]), and the initial mass function slope. All properties have significant gradients, confirming the existence of multiple structural components, also including a "blue spot" characterized by younger and metal-richer stars. We find that the component dominating the light budget of NGC 3311 within R<2.0kpc, is the surviving z=0 analogue of a high-z compact core, according to the definition of Pulsoni et al. (2021). This concentrated structure has a relatively small velocity dispersion (sigma~180km/s), is very old (ages~11Gyr), metal-rich ([Z/H]~0.2 and [Na/Fe]~0.4), and has a bottom-heavy IMF (with slope Gamma_b_~2.4). In the outer region, instead, the line-of-sight velocity distribution becomes increasingly broader, and the stars have younger age. They are also metal and sodium poorer but {alpha}-element richer. The low-mass end of the IMF slope becomes Chabrier-like with increasing galactocentric distances. The existence of multiple structural components in NGC 3311 from photometry, kinematics, and stellar populations confirms the predictions from the two-phase formation scenario for NGC 3311, according to which a first very short, high-z star formation episode formed a compact stellar structure in its core, which then grew in size by the extended mass assembly of relatively massive satellites. Interestingly, the outer stellar population has an overabundant [alpha/Fe], most likely because NGC 3311, located at the center of the galaxy cluster, accreted stars from rapidly quenched satellites.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/589/A139
- Title:
- Stellar populations of NGC 3311
- Short Name:
- J/A+A/589/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The history of the mass assembly of brightest cluster galaxies may be studied by mapping the stellar populations at large radial distances from the galaxy centre, where the dynamical times are long and preserve the chemodynamical signatures of the accretion events. To provide extended and robust measurements of the stellar population parameters in NGC 3311, the cD galaxy at the centre of the Hydra I cluster, and out to three effective radius. We wish to characterise the processes that drove the build up of the stellar light at all these radii. We obtained the spectra from several regions in NGC 3311 covering an area of ~3arcmin^2^ in the wavelength range 4800<lambda({AA})<5800, using the FORS2 spectrograph at the Very Large Telescope in the MXU mode. We measured the equivalent width of seven absorption-features defined in the Lick/IDS system, which were modelled by single stellar populations, to provide luminosity-weighted ages, metallicities, and alpha element abundances. The trends in the Lick indices and the distribution of the stellar population parameters indicate that the stars of NGC3311 may be divided in two radial regimes, one within and the another beyond one effective radius, R_e_=8.4kpc, similar to the distinction between the inner galaxy and the external halo derived from the NGC3311 velocity dispersion profile. The inner galaxy (R<R_e_) is old (age ~14Gyr), has negative metallicity gradients and positive alpha element gradients. The external halo is also very old, but has a negative age gradient. The metal and element abundances of the external halo both have a large scatter, indicating that stars from a variety of satellites with different masses have been accreted. The region in the extended halo associated with the off-centred envelope at 0<P.A.({deg})<90 (Arnaboldi et al., 2012A&A...545A..37A) has higher metallicity with respect to the symmetric external halo. The different stellar populations in the inner galaxy and extended halo reflect the dominance of in situ stars in the former and the accreted origin for the large majority of the stars in the latter. The low value of the velocity dispersion in the inner galaxy indicates that its stars are bound to the galaxy's gravitational potential, and the abundances and gradients suggest that the inner galaxy is formed in an outside-in scenario of merging gas-rich lumps, reminiscent of the first phase of galaxy formation. The external halo has a higher velocity dispersion, it is dynamically hotter than the galaxy and its stars are gravitationally driven by the cluster's gravitational potential. The stars in the external halo were removed from their parent galaxies, either disks with truncated star formation, or the outer regions of early-type galaxies. Late mass accretion at large radii is now coming from the tidal stripping of stars from dwarfs and S0 galaxies. These results provide supporting evidence for the recent theoretical models of formation of massive ellipticals as a two-phase process.
- ID:
- ivo://CDS.VizieR/J/MNRAS/313/469
- Title:
- Streaming motions of galaxy clusters. I.
- Short Name:
- J/MNRAS/313/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present paper is the first in a series presenting results of the "Streaming Motions of Abell Cluster" (SMAC) project. We present new spectroscopic data for 532 early-type galaxies, predominantly Abell cluster members with cz<12000km/s. We tabulate 919 individual measurements, from six observing runs, for recession velocity, cz, central velocity dispersion, {sigma}, and magnesium line-strength indices, Mg_2_ and Mgb. The median estimated error, per measurement, in {sigma} is 5 per cent. The Mg_2_ line-strength data have median errors of 0.009mag. The observed scatter between repeat measurements is largely accounted for by photon-counting errors. These data will be employed in forthcoming papers, where they will form part of a merged and standardized catalogue of Fundamental Plane data for use in cluster distance estimates and peculiar velocity analyses.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1002
- Title:
- Stroemgren photometry in Abell 2125 and 2218
- Short Name:
- J/AJ/130/1002
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine new narrowband photometry with archival Wide Field Planetary Camera 2 (WFPC2) data for A2218 (z=0.18) and A2125 (z=0.25), two clusters with intermediate redshifts but very different cluster properties, in order to examine the evolution of galaxy populations. A2218 is a dense, elliptical-rich cluster (Bautz-Morgan type II) similar to the Coma Cluster in its evolutionary appearance, whereas A2125 is a less dense, more open cluster (Bautz-Morgan type II-III), although similar in richness to A2218.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/22
- Title:
- Strong and weak lensing analysis of A2261
- Short Name:
- J/ApJ/757/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We precisely constrain the inner mass profile of A2261 (z=0.225) for the first time and determine that this cluster is not "overconcentrated" as found previously, implying a formation time in agreement with {Lambda}CDM expectations. These results are based on multiple strong-lensing analyses of new 16-band Hubble Space Telescope imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble (CLASH; Postman et al. 2012, Cat. J/ApJS/199/25). Combining this with revised weak-lensing analyses of Subaru wide-field imaging with five-band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass M_vir_=(2.2+/-0.2)x10^15^M_{sun}_h^-1^_70_ (within r_vir_{approx}3Mpc.h^-1^_70_) and concentration c_vir_=6.2+/-0.3 when assuming a spherical halo. This agrees broadly with average c(M, z) predictions from recent {Lambda}CDM simulations, which span 5<~<c><~8. Our most significant systematic uncertainty is halo elongation along the line of sight (LOS). To estimate this, we also derive a mass profile based on archival Chandra X-ray observations and find it to be ~35% lower than our lensing-derived profile at r_2500_~600kpc. Agreement can be achieved by a halo elongated with a ~2:1 axis ratio along our LOS. For this elongated halo model, we find M_vir_=(1.7+/-0.2)x10^15^M_{sun}_h^-1^_70_ and c_vir_=4.6+/-0.2, placing rough lower limits on these values. The need for halo elongation can be partially obviated by non-thermal pressure support and, perhaps entirely, by systematic errors in the X-ray mass measurements. We estimate the effect of background structures based on MMT/Hectospec spectroscopic redshifts and find that these tend to lower M_vir_ further by ~7% and increase c_vir_by ~5%.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/114
- Title:
- Strong lensing mass modeling of 4 HFF clusters
- Short Name:
- J/ApJ/819/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct precise strong lensing mass modeling of four Hubble Frontier Field (HFF) clusters, Abell 2744, MACS J0416.1-2403, MACS J0717.5+3745, and MACS J1149.6+2223, for which HFF imaging observations are completed. We construct a refined sample of more than 100 multiple images for each cluster by taking advantage of the full-depth HFF images, and conduct mass modeling using the glafic software, which assumes simply parametrized mass distributions. Our mass modeling also exploits a magnification constraint from the lensed SN Ia HFF14Tom for Abell 2744 and positional constraints from the multiple images S1-S4 of the lensed supernova SN Refsdal for MACS J1149.6+2223. We find that our best-fitting mass models reproduce the observed image positions with rms errors of ~0.4", which are smaller than rms errors in previous mass modeling that adopted similar numbers of multiple images. Our model predicts a new image of SN Refsdal with a relative time delay and magnification that are fully consistent with a recent detection of reappearance. We then construct catalogs of z~6-9 dropout galaxies behind the four clusters and estimate magnification factors for these dropout galaxies with our best-fitting mass models. The dropout sample from the four cluster fields contains ~120 galaxies at z>~6, about 20 of which are predicted to be magnified by a factor of more than 10. Some of the high-redshift galaxies detected in the HFF have lensing-corrected magnitudes of M_UV_~-15 to -14. Our analysis demonstrates that the HFF data indeed offer an ideal opportunity to study faint high-redshift galaxies. All lensing maps produced from our mass modeling will be made available on the Space Telescope Science Institute website (https://archive.stsci.edu/prepds/frontier/lensmodels/).
- ID:
- ivo://CDS.VizieR/J/A+A/632/A36
- Title:
- Strong lensing models of 8 CLASH clusters
- Short Name:
- J/A+A/632/A36
- Date:
- 09 Nov 2021
- Publisher:
- CDS
- Description:
- We carry out a detailed strong lensing analysis of a sub-sample of eight galaxy clusters of the Cluster Lensing And Supernova survey with Hubble (CLASH), in the redshift range of z_cluster_=[0.23-0.59], using extensive spectroscopic information, primarily from the Multi Unit Spectroscopic Explorer (MUSE) archival data and complemented with CLASH-VLT redshift measurements. The observed positions of the multiple images of strongly lensed background sources are used to constrain parametric models describing the cluster total mass distributions. Different models are tested in each cluster depending on the complexity of its mass distribution and on the number of detected multiple images. Four clusters show more than five spectroscopically confirmed multiple image families. In this sample, we do not make use of families that are only photometrically identified, in order to reduce model degeneracies between the values of the total mass of a cluster and of the source redshifts, and systematics due to the potential misidentifications of some multiple images. For the remaining four systems, we use additional families without any spectroscopic confirmation to increase the number of strong lensing constraints up to the number of free parameters in our parametric models. We present spectroscopic confirmation of 27 multiply lensed sources, with no previous spectroscopic measurements, spanning over the redshift range of z_src_=[0.7-6.1]. Moreover, we confirm an average of 48 galaxy members in the core of each cluster, thanks to the high efficiency and large field of view of MUSE. We use this information to derive precise strong lensing models, projected total mass distributions and magnification maps. We show that, despite having different properties (i.e., number of mass components, total mass, redshift, etc), the projected total mass and mass density profiles of all clusters have very similar shapes, when rescaled by independent measurements of M200c and R200c. Specifically, we measure the mean value of the projected total mass of our cluster sample within 10 (20)% of R200c to be 0.13 (0.32) of M200c, with a remarkably small scatter of 5 (6)%. Furthermore, the large number of high-z sources and the precise magnification maps derived in this work for four clusters add up to the sample of high-quality gravitational telescopes to be used to study the faint and distant Universe.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/12
- Title:
- Strong lens models for 37 clusters from SGAS
- Short Name:
- J/ApJS/247/12
- Date:
- 08 Mar 2022 13:45:09
- Publisher:
- CDS
- Description:
- We present strong gravitational lensing models for 37 galaxy clusters from the Sloan Digital Sky Survey Giant Arcs Survey (SGAS). We combine data from multi-band Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging, with ground-based imaging and spectroscopy from Magellan, Gemini, Apache Point Observatory, and the Multiple Mirror Telescope, in order to detect and spectroscopically confirm new multiply imaged lensed background sources behind the clusters. We report spectroscopic or photometric redshifts of sources in these fields, including cluster galaxies and background sources. Based on all available lensing evidence, we construct and present strong-lensing mass models for these galaxy clusters. The clusters span a redshift range of 0.176<z<0.66 with a median redshift of z=0.45, and sample a wide range of dynamical masses, 1.5<M_200_<35x10^14^M_{sun}_, as estimated from their velocity dispersions. As these clusters were selected as lenses primarily owing to a fortuitous alignment with background galaxies that results in giant arcs, they exhibit a wide range in Einstein radii, 1.3"<{theta}_E_<23.1" for a source at z=2, with a median {theta}_E_=10.8".
- ID:
- ivo://CDS.VizieR/J/ApJ/799/95
- Title:
- Structure in 3D galaxy distribution. II. Voids
- Short Name:
- J/ApJ/799/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The major uncertainties in studies of the multi-scale structure of the universe arise not from observational errors but from the variety of legitimate definitions and detection methods for individual structures. To facilitate the study of these methodological dependencies, we have carried out 12 different analyses defining structures in various ways. This has been done in a purely geometrical way by utilizing the HOP (Eisenstein+, 1998ApJ...498..137E) algorithm as a unique parameter-free method of assigning groups of galaxies to local density maxima or minima. From three density estimation techniques (smoothing kernels, Bayesian blocks, and self-organizing maps) applied to three data sets (the Sloan Digital Sky Survey Data Release 7, the Millennium simulation, and randomly distributed points) we tabulate information that can be used to construct catalogs of structures connected to local density maxima and minima. We also introduce a void finder that utilizes a method to assemble Delaunay tetrahedra into connected structures and characterizes regions empty of galaxies in the source catalog.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/1116
- Title:
- Structure of early-type galaxies
- Short Name:
- J/MNRAS/358/1116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the Photometric Plane (PHP), namely the relation between the effective radius r_e_, the mean surface brightness within that radius {mu}_e_ and the Sersic index n, in optical (R and I) and near-infrared (NIR; K) bands for a large sample of early-type galaxies (ETGs) in the rich cluster MS 1008 at z=0.306.
