- ID:
- ivo://CDS.VizieR/J/ApJ/764/135
- Title:
- Spectroscopic redshifts of BL Lac objects
- Short Name:
- J/ApJ/764/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on spectroscopic observations covering most of the 475 BL Lacs in the second Fermi Large Area Telescope (LAT) catalog of active galactic nuclei (AGNs). Including archival measurements (correcting several erroneous literature values) we now have spectroscopic redshifts for 44% of the BL Lacs. We establish firm lower redshift limits via intervening absorption systems and statistical lower limits via searches for host galaxies for an additional 51% of the sample leaving only 5% of the BL Lacs unconstrained. The new redshifts raise the median spectroscopic {overline}{Z} from 0.23 to 0.33 and include redshifts as large as z=2.471. Spectroscopic redshift minima from intervening absorbers have {overline}{Z}, showing a substantial fraction at large z and arguing against strong negative evolution. We find that detected BL Lac hosts are bright ellipticals with black hole masses M_{bullet}_~10^8.5^-10^9^, substantially larger than the mean of optical AGNs and LAT Flat Spectrum Radio Quasar samples. A slow increase in M_{bullet}_ with z may be due to selection bias. We find that the power-law dominance of the optical spectrum extends to extreme values, but this does not strongly correlate with the {gamma}-ray properties, suggesting that strong beaming is the primary cause of the range in continuum dominance.
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- ID:
- ivo://CDS.VizieR/J/ApJ/776/91
- Title:
- Spectroscopic redshifts of galaxies in 2 clusters
- Short Name:
- J/ApJ/776/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide a new observational test for a key prediction of the {Lambda}CDM cosmological model: the contributions of mergers with different halo-to-main-cluster mass ratios to cluster-sized halo growth. We perform this test by dynamically analyzing 7 galaxy clusters, spanning the redshift range 0.13<z_c_<0.45 and caustic mass range 0.4-1.5x10^15^h_0.73_^-1^M_{sun}_, with an average of 293 spectroscopically confirmed bound galaxies to each cluster. The large radial coverage (a few virial radii), which covers the whole infall region, with a high number of spectroscopically identified galaxies enables this new study. For each cluster, we identify bound galaxies. Out of these galaxies, we identify infalling and accreted halos and estimate their masses and their dynamical states. Using the estimated masses, we derive the contribution of different mass ratios to cluster-sized halo growth. For mass ratios between ~0.2 and ~0.7, we find a ~1{sigma} agreement with {Lambda}CDM expectations based on the Millennium simulations I and II. At low mass ratios, <~0.2, our derived contribution is underestimated since the detection efficiency decreases at low masses, ~2x10^14^h_0.73_^-1^M_{sun}_. At large mass ratios, >~0.7, we do not detect halos probably because our sample, which was chosen to be quite X-ray relaxed, is biased against large mass ratios. Therefore, at large mass ratios, the derived contribution is also underestimated.
- 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/ApJ/878/66
- Title:
- Spectroscopic redshifts of gal. in SPT-CLJ0615-5746
- Short Name:
- J/ApJ/878/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of spectroscopic redshifts for SPT-CLJ0615-5746, the most distant cluster in the Reionization Lensing Cluster Survey. Using Nod & Shuffle multislit observations with LDSS-3 on Magellan, we identify ~50 cluster members and derive a cluster redshift of z_c_=0.972, with a velocity dispersion of {sigma}=1244+/-162km/s. We calculate a cluster mass using a {sigma}_200_-M_200_ scaling relation of M_200_=(9.6+/-3.5)x10^14^M_{sun}_, in agreement with previous, independent mass measurements of this cluster. In addition, we examine the kinematic state of SPT-CLJ0615-5746, taking into consideration prior investigations of this system. With an elongated profile in lensing mass and X-ray emission, a non-Gaussian velocity dispersion that increases with clustercentric radius, and a brightest cluster galaxy not at rest with the bulk of the system, there are multiple cluster properties that, while not individually compelling, combine to paint a picture that SPT-CLJ0615-5746 is currently being assembled.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A49
- Title:
- Spectroscopic study of CEMP-(s and r/s) stars
- Short Name:
- J/A+A/649/A49
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The origin of the enhanced abundances of both s- and r-process elements observed in a subclass of Carbon-Enhanced Metal-Poor (CEMP) stars, i.e., CEMP-r/s stars, still remains poorly understood. The i-process nucleosynthesis has been suggested as one of the most promising mechanisms for the origin of these stars. To better understand the chemical signatures and formation mechanism(s) of five previously claimed potential CH star candidates HE 0017+0055, HE 2144-1832, HE 2339-0837, HD 145777 and CD-27 14351 through a detailed systematic follow-up spectroscopic study based on high-resolution spectra. The stellar atmospheric parameters, the effective temperature T_eff_, the microturbulent velocity {zeta}, the surface gravity logg, and the metallicity [Fe/H] are derived from local thermodynamic equilibrium analyses using model atmospheres. Elemental abundances of C, N, {alpha}-elements, iron-peak elements and several neutron-capture elements are estimated using the equivalent width measurement technique as well as spectrum synthesis calculations in some cases. In the context of the double enhancement observed in four of the programme stars, we have critically examined if the literature i-process model yields ([X/Fe]) of heavy elements can explain the observed abundance distribution. The estimated metallicity [Fe/H] of the programme stars ranges from -1.63 to -2.74. All the five stars show enhanced abundance for Ba and four of them exhibit enhanced abundance for Eu. Based on our analysis, HE 0017+0055, HE 2144-1832 and HE 2339-0837 are found to be CEMP-r/s stars, whereas HD 145777 and CD-27 14351 show characteristic properties of CEMP-s stars. From a detailed analysis of different classifiers of CEMP stars, we have identified the one which best describes the CEMP-s and CEMP-r/s stars. We found that for both CEMP-s and CEMP-r/s stars, [Ba/Eu] and [La/Eu] exhibit positive values and [Ba/Fe]>=1.0. However, CEMP-r/s stars satisfy [Eu/Fe]>=1.0, 0.0<=[Ba/Eu]<=1.0 and/or 0.0<=[La/Eu]<=0.7. CEMP-s stars normally show [Eu/Fe]<1.0 with [Ba/Eu]>0.0 and/or [La/Eu]>0.5. If [Eu/Fe]~>=1.0, then the condition on [Ba/Eu] and/or [La/Eu] for a star to be a CEMP-s star is [Ba/Eu]>1.0 and/or [La/Eu]>0.7. Using a large sample of similar stars from the literature we have examined if [hs/ls] alone can be used as a classifier, and if there are any limiting values for [hs/ls] ratio that can be used to distinguish CEMP-s and CEMP-r/s stars. In spite of peaking at different values of [hs/ls], CEMP-s and CEMP-r/s stars show an overlap in the range 0.0<[hs/ls]<1.5 ,and hence, this ratio cannot be used to distinguish CEMP-s and CEMP-r/s stars. We have noticed a similar overlap in the case of [Sr/Ba] ratio as well, in the range -1.6<[Sr/Ba]<-0.5 and hence, this ratio also cannot be used to separate the two subclasses, CEMP-s and CEMP-r/s.
- ID:
- ivo://CDS.VizieR/J/MNRAS/378/1507
- Title:
- Spectroscopic study of 6 galaxies
- Short Name:
- J/MNRAS/378/1507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an examination of the kinematics and stellar populations of a sample of three brightest group galaxies (BGGs) and three brightest cluster galaxies (BCGs) in X-ray groups and clusters. We have obtained high signal-to-noise ratio Gemini/Gemini South Multi-Object Spectrograph (GMOS) long-slit spectra of these galaxies and use Lick indices to determine ages, metallicities and alpha-element abundance ratios out to at least their effective radii. We find that the BGGs and BCGs have very uniform masses, central ages and central metallicities.
- 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/AJ/135/1117
- Title:
- Spectroscopic study of red giants in M15
- Short Name:
- J/AJ/135/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectra of 110 selected red giant stars in the globular cluster M15 (NGC 7078) were obtained with Hectochelle at the MMT telescope in 2005 May, 2006 May, and 2006 October. Echelle orders containing H{alpha} and CaII H&K are used to identify emission and line asymmetries characterizing motions in the extended atmospheres. Emission in H{alpha} is detected to a luminosity of log(L/L_{sun}_)=2.36, in this very metal-deficient cluster, comparable to other studies, suggesting that the appearance of emission wings is independent of stellar metallicity. The faintest stars showing H{alpha} emission appear to lie on the asymptotic giant branch (AGB) in M15. A line-bisector technique for H{alpha} reveals outflowing velocities in all stars brighter than log(L/L_{sun}_)=2.5, and this outflow velocity increases with stellar luminosity, indicating the mass outflow increases smoothly with luminosity. Many stars lying low on the AGB show exceptionally high outflow velocities (up to 10-15km/s) and more velocity variability (up to 6-8km/s) than red giant branch (RGB) stars of similar apparent magnitude. High velocities in M15 may be related to the low cluster metallicity. Dusty stars identified from Spitzer Space Telescope infrared photometry as AGB stars are confirmed as cluster members by radial velocity measurements, yet their H{alpha} profiles are similar to those of RGB stars without dust. If substantial mass loss creates the circumstellar shell responsible for infrared emission, such mass loss must be episodic.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/397
- Title:
- Spectroscopic study of RGs in the Kepler field
- Short Name:
- J/MNRAS/450/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Thanks to the recent very high precision photometry of red giants from satellites such as Kepler, precise mass and radius values as well as accurate information of evolutionary stages are already established by asteroseismic approach for a large number of G-K giants. Based on the high-dispersion spectra of selected such 55 red giants in the Kepler field with precisely known seismic parameters (among which parallaxes are available for nine stars), we checked the accuracy of the determination method of stellar parameters previously applied to many red giants by Takeda et al. (2008PASJ...60..781T), since it may be possible to discriminate their complex evolutionary status by using the surface gravity versus mass diagram. We confirmed that our spectroscopic gravity and the seismic gravity satisfactorily agree with each other (to within ~0.1 dex) without any systematic difference. However, the mass values of He-burning red clump giants derived from stellar evolutionary tracks (~2-3 M_{sun}_) were found to be markedly larger by ~50 percent compared to the seismic values (~1-2 M_{sun}_) though such discrepancy is not seen for normal giants in the H-burning phase, which reflects the difficulty of mass determination from intricately overlapping tracks on the luminosity versus effective temperature diagram. This consequence implies that the mass results of many red giants in the clump region determined by Takeda et al. are likely to be significantly overestimated. We also compare our spectroscopically established parameters with recent literature values, and further discuss the prospect of distinguishing the evolutionary status of red giants based on the conventional (i.e. non-seismic) approach.
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