- ID:
- ivo://CDS.VizieR/J/ApJ/751/46
- Title:
- Spectroscopic observations in VV124 (UGC 4879)
- Short Name:
- J/ApJ/751/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial velocities for different components of the galaxy, and photometry hinted at the presence of a stellar disk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS). We validated members based on their positions in the color-magnitude diagram, radial velocities, and spectral features. Our sample contains 67 members. The average radial velocity is <v_r_>=-29.1+/-1.3km/s in agreement with the previous radio measurements of H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by velocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an upper limit of 8.6km/s on any rotation in the photometric disk-like feature. The velocity dispersion is {sigma}_v_=9.4+/-1.0km/s, from which we inferred a mass of M_1/2_=(2.1 +/-0.2)x10^7^M_{sun}_ and a mass-to-light ratio of (M/L_V_)_1/2_=5.2+/-1.1M_{sun}_/L_{sun}_, both measured within the half-light radius. Thus, VV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines. The average metallicity, <[Fe/H]>=-1.14+/-0.06, is consistent with the mass-metallicity relation defined by dSph galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/841/7
- Title:
- Spectroscopic obs & members of ZwCl 2341+0000
- Short Name:
- J/ApJ/841/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ZwCl 2341.1+0000, a merging galaxy cluster with disturbed X-ray morphology and widely separated (~3Mpc) double radio relics, was thought to be an extremely massive (10-30x10^14^M_{sun}_) and complex system, with little known about its merger history. We present JVLA 2-4GHz observations of the cluster, along with new spectroscopy from our Keck/DEIMOS survey, and apply Gaussian Mixture Modeling to the three-dimensional distribution of 227 confirmed cluster galaxies. After adopting the Bayesian Information Criterion to avoid overfitting, which we discover can bias high the total dynamical mass estimates, we find that a three-substructure model with a total dynamical mass estimate of 9.39+/-0.81x10^14^M_{sun}_ is favored. We also present deep Subaru imaging and perform the first weak lensing analysis on this system, obtaining a weak lensing mass estimate of 5.57+/-2.47x10^14^M_{sun}_. This is a more robust estimate because it does not depend on the dynamical state of the system, which is disturbed due to the merger. Our results indicate that ZwCl2341.1+0000 is a multiple merger system comprised of at least three substructures, with the main merger that produced the radio relics occurring near the plane of the sky, and a younger merger in the north occurring closer to the line of sight. Dynamical modeling of the main merger reproduces observed quantities (relic positions and polarizations, subcluster separation and radial velocity difference), if the merger axis angle of ~10_-6_^+34^ degrees and the collision speed at pericenter is ~1900_-200_^+300^km/s.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/39
- Title:
- Spectroscopic properties of BOSS compact galaxies
- Short Name:
- J/ApJ/793/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive compact systems at 0.2<z<0.6 are the missing link between the predominantly compact population of massive quiescent galaxies at high redshift and their analogs and relics in the local volume. The evolution in number density of these extreme objects over cosmic time is the crucial constraining factor for the models of massive galaxy assembly. We select a large sample of ~200 intermediate-redshift massive compacts from the Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopy by identifying point-like Sloan Digital Sky Survey photometric sources with spectroscopic signatures of evolved redshifted galaxies. A subset of our targets have publicly available high-resolution ground-based images that we use to augment the dynamical and stellar population properties of these systems by their structural parameters. We confirm that all BOSS compact candidates are as compact as their high-redshift massive counterparts and less than half the size of similarly massive systems at z~0. We use the completeness-corrected numbers of BOSS compacts to compute lower limits on their number densities in narrow redshift bins spanning the range of our sample. The abundance of extremely dense quiescent galaxies at 0.2<z<0.6 is in excellent agreement with the number densities of these systems at high redshift. Our lower limits support the models of massive galaxy assembly through a series of minor mergers over the redshift range 0<z<2.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/102
- Title:
- Spectroscopic redshift catalog in A2142 field
- Short Name:
- J/ApJ/863/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To investigate the dynamics of the galaxy cluster A2142, we compile an extended catalog of 2239 spectroscopic redshifts of sources, including 237 newly measured redshifts, within 30 arcmin from the cluster center. With the {sigma}-plateau algorithm from the caustic method, we identify 868 members and a number of substructures in the galaxy distribution both in the outskirts, out to ~3.5Mpc from the cluster center, and in the central region. In the outskirts, one substructure overlaps a falling clump of gas previously identified in the X-ray band. These substructures suggest the presence of multiple minor mergers, which are responsible for the complex dynamics of A2142, and the absence of recent or ongoing major mergers. We show that the distribution of the galaxies in the cluster core and in several substructures is consistent with the mass distribution inferred from the weak-lensing signal. Moreover, we use spatially resolved X-ray spectroscopy to measure the redshift of different regions of the intracluster medium within ~3 arcmin from the cluster center. We find a ring of gas near the two X-ray cold fronts identified in previous analyses and measure a velocity of this ring of 810+/-330km/s larger than the cluster mean velocity. Our analysis suggests the presence of another ring surrounding the core, whose velocity is 660+/-300km/s larger than the cluster velocity. These X-ray features are not associated with any optical substructures, and support the core-sloshing scenario suggested in previous work.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/139
- Title:
- Spectroscopic redshifts of galaxies in groups
- Short Name:
- J/ApJ/756/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the global group properties of two samples of galaxy groups containing 39 high-quality X-ray-selected systems and 38 optically (spectroscopically) selected systems in coincident spatial regions at 0.12<z<0.79. The total mass range of the combined sample is ~(10^12^-5)x10^14^M_{sun}_. Only nine optical systems are associable with X-ray systems. We discuss the confusion inherent in the matching of both galaxies to extended X-ray emission and of X-ray emission to already identified optical systems. Extensive spectroscopy has been obtained and the resultant redshift catalog and group membership are provided here. X-ray, dynamical, and total stellar masses of the groups are also derived and presented. We explore the effects of utilizing different centers and applying three different kinds of radial cut to our systems: a constant cut of 1Mpc and two r_200_ cuts, one based on the velocity dispersion of the system and the other on the X-ray emission.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/21
- Title:
- Spectroscopic redshifts of galaxies in MACS
- Short Name:
- J/ApJS/211/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 1921 spectroscopic redshifts measured in the fields of the massive galaxy clusters MACSJ0416.1-2403 (z=0.397), MACSJ0717.5+3745 (z=0.546), and MACSJ1149.5+2223 (z=0.544), i.e., three of the four clusters selected by Space Telescope Science Institute as the targets of the Frontier Fields (FFs) initiative for studies of the distant Universe via gravitational lensing. Compiled in the course of the Massive Cluster Survey project (MACS) that detected the FF clusters, this catalog is provided to the community for three purposes: (1) to allow the identification of cluster members for studies of the galaxy population of these extreme systems, (2) to facilitate the removal of unlensed galaxies and thus reduce shear dilution in weak-lensing analyses, and (3) to improve the calibration of photometric redshifts based on both ground- and spacebased observations of the FF clusters.
- ID:
- ivo://CDS.VizieR/J/PAZh/27/381
- Title:
- Spectroscopic study of BM Ori
- Short Name:
- J/PAZh/27/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two CCD spectra of the star BM Ori were obtained with the echelle spectrograph of the 6-m telescope. Measured line equivalent widths were used to estimate atmospheric parameters of the secondary star.
- ID:
- ivo://CDS.VizieR/J/ApJ/694/L144
- Title:
- Spectroscopic study of Leo V dSph
- Short Name:
- J/ApJ/694/L144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic study of Leo V, a recently discovered satellite of the Milky Way (MW). From stellar spectra obtained with the MMT/Hectochelle spectrograph we identify seven likely members of Leo V. Five cluster near the Leo V center (R<3') and have a velocity dispersion of 2.4^+2.4^_1.4_km/s. The other two likely members lie near each other but far from the center (R~13'~700pc) and inflate the global velocity dispersion to 3.7^+2.3^_1.4_km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/519/A40
- Title:
- Spectroscopic study of 65 nearby galaxies
- Short Name:
- J/A+A/519/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the aim of constraining the source of excitation and the origin of the ionized gas in early-type galaxies (ETGs), we analyzed intermediate resolution optical spectra of a sample of 65 ETGs mostly located in low density environments. Optical emission lines are detected in 89% of the sample. The incidence and strength of emission do not correlate either with the E/S0 classification, or with the fast/slow rotator classification. Comparing the nuclear r<r_e_/16 line emission with the classical [OIII]/Hb vs [NII]/Ha diagnostic diagram, the galaxy activity is so classified: 72% of the galaxies with emission are LINERs, 9% are Seyferts, 12% are Composite/Transition objects, and 7% are non-classified. Seyferts have young luminosity-weighted ages (<5Gyr), and appear, on average, significantly younger than LINERs and Composites. Excluding the Seyferts from our sample, we find that the spread in the ([OIII], Ha or [NII]) emission strength increases with the galaxy central velocity dispersion sigma_c_. The [NII]/Ha ratio decreases with increasing galacto-centric distance, indicating either a decrease of the nebular metallicity, or a progressive "softening" of the ionizing spectrum. The average oxygen abundance of the ionized gas is slightly less than solar, and a comparison with the results obtained in Paper III (Cat. J/A+A/463/455) from Lick indices reveals that it is ~0.2dex lower than that of stars. Conclusions: the nuclear emission can be explained with photoionization by PAGB stars alone only in ~22% of the LINERs/Composite sample. On the other hand, we can not exclude an important role of PAGB star photoionization at larger radii. For the major fraction of the sample, the nuclear emission is consistent with excitation from a low-accretion rate AGN, fast shocks (200-500km/s) in a relatively gas-poor environment (n<100cm^-3^), or coexistence of the two. The derived nebular metallicities suggest either an external origin of the gas, or an overestimate of the oxygen yields by SN models.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1748
- Title:
- Spectroscopic study of Segue 2
- Short Name:
- J/MNRAS/397/1748
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope (MMT). From this, we derive a luminosity of Mv=-2.5, a half-light radius of 34pc and a systemic velocity of ~-40km/s. Our data also provide evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighbouring fields. We resolve the velocity dispersion of Segue 2 as 3.4km/s and the possible stream as ~7km/s. This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites - survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts z>10 and are good candidates for fossils of the reionization epoch.