- ID:
- ivo://CDS.VizieR/J/ApJ/880/142
- Title:
- Spectroscopic members of COSMOS X-ray systems
- Short Name:
- J/ApJ/880/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate spectroscopic properties of galaxy systems identified based on deep X-ray observations in the Cosmic Evolution Survey (COSMOS) field. The COSMOS X-ray system catalog we use includes 180 X-ray systems to a limiting flux of 1.0x10^-15^erg/cm^2^/s, an order of magnitude deeper than the future e-ROSITA survey. We identify spectroscopic members of these X-ray systems based on the spectroscopic catalog constructed by compiling various spectroscopic surveys including 277 new measurements; 146 X-ray systems are spectroscopically identified groups with more than three spectroscopic members. We identify 2196 spectroscopic redshifts of member candidates in these X-ray systems. The X-ray luminosity (L_X_)-velocity dispersion ({sigma}_v_) scaling relation of the COSMOS X-ray systems is consistent with that of massive X-ray clusters. One of the distinctive features of the COSMOS survey is that it covers the X-ray luminosity range where poor groups overlap the range for extended emission associated with individual quiescent galaxies. We assess the challenges posed by the complex morphology of the distribution of systems with low X-ray luminosity, including groups and individual quiescent galaxies, in the L_x_-{sigma}_v_ plane.
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- 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/A+A/504/829
- Title:
- Spectroscopic survey of youngest field stars
- Short Name:
- J/A+A/504/829
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of an ambitious ground-based observation programme conducted on 1-4m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical (Tycho Catalogue) counterparts of ROSAT All- Sky Survey X-ray sources in the northern hemisphere. In this paper, we concentrate on the optically brightest (VT<=9.5m) candidates (704 objects).We acquired high-resolution optical spectroscopy in the H{alpha} and/or lithium spectral regions for 426 of such stars without relevant data in the literature. We describe the star sample and the observations and we start to discuss the physical properties of the investigated stars.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A96
- Title:
- Spectroscopic survey of youngest field stars II.
- Short Name:
- J/A+A/612/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation in the solar neighborhood is mainly traced by young stars in open clusters, associations, and in the field, which can be identified, for example, by their X-ray emission. The determination of stellar parameters for the optical counterparts of X-ray sources is crucial for a full characterization of these stars. This work extends the spectroscopic study of the RasTyc sample, obtained by the cross-correlation of the TYCHO and ROSAT All-Sky Survey catalogs, to stars fainter than V=9.5mag and aims to identify sparse populations of young stars in the solar neighborhood. We acquired 625 high-resolution spectra for 443 presumably young stars with four different instruments in the northern hemisphere. The radial and rotational velocity (vsini) of our targets were measured by means of the cross-correlation technique, which is also helpful to discover single-lined (SB1), double-lined spectroscopic binaries (SB2), and multiple systems. We used the code ROTFIT to perform an MK spectral classification and to determine the atmospheric parameters (Teff, logg, [Fe/H]) and and vsini of the single stars and SB1 systems. For these objects, we used the spectral subtraction of slowly rotating templates to measure the equivalent widths of the H{alpha} and LiI-6708A lines, which enabled us to derive their chromospheric activity level and lithium abundance. We made use of Gaia DR1 parallaxes and proper motions to locate the targets in the HR diagram and to compute the space velocity components of the youngest objects. We find a remarkable percentage (at least 35%) of binaries and multiple systems. On the basis of the lithium abundance, the sample of single stars and SB1 systems appears to be mostly (about 60%) composed of stars younger than the members of the UMa cluster. The remaining sources are in the age range between the UMa and Hyades clusters (about 20%) or older (20%). In total, we identify 42 very young (PMS-like) stars, which lie above or very close to the Pleiades upper envelope of the lithium abundance. A significant percentage (about 12%) of evolved stars (giants and subgiants) is also present in our sample. Some of these stars are also lithium rich (A(Li)>1.4).
- ID:
- ivo://CDS.VizieR/J/A+A/500/947
- Title:
- Spectroscopy and photometry in A2744 and A2537
- Short Name:
- J/A+A/500/947
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The current paradigm of cosmic formation and evolution of galaxy clusters foresees growth mostly through merging. Galaxies in the infall region or in the core of a cluster undergo transformations owing to different environmental stresses. For two X-ray luminous clusters at redshift z~0.3 with opposite X-ray morphologies (i.e., dynamical states), RXCJ0014.3-3022 and RXCJ2308.3-0211, we assess differences in galaxy populations as a function of cluster topography. This is a pilot study for the joint X-ray and optical analysis of the REFLEX-DXL cluster sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/2615
- Title:
- Spectroscopy of galaxies in the SSA22 field
- Short Name:
- J/MNRAS/450/2615
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Very Large Telescope VIMOS, Keck DEIMOS and Keck LRIS multi-object spectra of 367 sources in the field of the z~3.09 protocluster SSA22. Sources are spectroscopically classified via template matching, allowing new identifications for 206 extragalactic sources, including 36 z>2 Lyman-break galaxies (LBGs) and Lyman alpha emitters (LAEs), eight protocluster members, and 94 X-ray sources from the ~400ks Chandra deep survey of SSA22. Additionally, in the area covered by our study, we have increased by ~4, 13, and 6 times the number of reliable redshifts of sources at 1.0<z<2.0, at z>3.4, and with X-ray emission, respectively. We compare our results with past spectroscopic surveys of SSA22 to investigate the completeness of the LBGs and the X-ray properties of the new spectroscopically classified sources in the SSA22 field.
- ID:
- ivo://CDS.VizieR/J/AJ/149/195
- Title:
- Spectroscopy of the quadruple system HD 91962
- Short Name:
- J/AJ/149/195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young nearby solar-type star HD 91962 is a rare quadruple system where three companions revolve around the main component with periods of 170.3days, 8.85years, and 205years. The two outer orbits are nearly co-planar, and all orbits have small eccentricities. We refine the visual orbit of the outer pair and determine the combined spectro-interferometric orbit of the middle 8.8year pair and the spectroscopic orbit of the inner binary. The middle and inner orbits are likely locked in a 1:19 resonance, and the ratio of the outer and middle periods is ~23. The masses of all components are estimated (inside-out: 1.14, 0.32, 0.64, 0.64 solar mass). The dynamical parallax is 27.4+/-0.6mas. We speculate that this multiple system originated from collapse of an isolated core and that the companions migrated in a dissipative disk. Other multiple systems with similar features (co-planarity, small eccentricity, and period ratio around 20) are known.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/1713
- Title:
- Spectroscopy of X-ray sources in ECDF-S
- Short Name:
- J/ApJ/693/1713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of our optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South. A total of 339 sources were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. We measured redshifts for 186 X-ray sources, including archival data and a literature search. We find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley". The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2223
- Title:
- SPICES II: CHANDRA observations of Lynx
- Short Name:
- J/AJ/123/2223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our first results on field X-ray sources detected in a deep, 184.7ks observation with the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx field (RA=08h48min, DE=+44{deg}54') of SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey, which contains three known X-ray-emitting clusters at redshifts of z=0.57, 1.26, and 1.27. Not including the known clusters, in the 17'x17' ACIS-I field we detect 132 sources in the 0.5-2keV (soft) X-ray band down to a limiting flux of ~1.7x10^-16^ergs/cm^2^/s and 11 sources in the 2-10keV (hard) X-ray band down to a limiting flux of ~1.3x10^-15^ergs/cm^2^/s. The combined catalog contains a total of 153 sources, of which 42 are detected only in the soft band and 21 are detected only in the hard band. Confirming previous Chandra results, we find that the fainter sources have harder X-ray spectra, providing a consistent solution to the long-standing "spectral paradox." From deep optical and near-infrared follow-up data, 77% of the X-ray sources have optical counterparts to I=24, and 71% of the X-ray sources have near-infrared counterparts to Ks=20. Four of the 24 sources in the near-IR field are associated with extremely red objects (EROs; I-Ks>=4). We have obtained spectroscopic redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These sources comprise a mix of broad-lined active galaxies, apparently normal galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic source is identified with an M7 dwarf exhibiting nontransient, hard X-ray emission. Thirteen of the Chandra sources are located within regions for which we have Hubble Space Telescope imaging. Nine of the sources are detected, showing a range of morphologies: several show compact cores embedded within diffuse emission, while others are spatially extended showing typical galaxy morphologies. Two of the Chandra sources in this subsample appear to be associated with mergers. We briefly review non-active galactic nucleus mechanisms to produce X-ray emission and discuss properties of the Lynx Chandra sample in relation to other samples of X-ray and non-X-ray sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/2239
- Title:
- SPIRE (f250um>17.4mJy) GOODS-N galaxies
- Short Name:
- J/MNRAS/417/2239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the first time, we investigate the X-ray/infrared (IR) correlation for star-forming galaxies (SFGs) at z~1, using SPIRE submm data from the recently launched Herschel Space Observatory and deep X-ray data from the 2-Ms Chandra Deep Field-North survey. We examine the X-ray/IR correlation in the soft X-ray (SX; 0.5-2keV) and hard X-ray (HX; 2-10keV) bands by comparing our z~1 SPIRE-detected SFGs to equivalently IR-luminous (L_IR_>10^10^L_{sun}_) samples in the local/low-redshift Universe.