- ID:
- ivo://CDS.VizieR/J/A+A/564/A85
- Title:
- Galaxy properties in clusters. II.
- Short Name:
- J/A+A/564/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the properties of galaxies on the outskirts of clusters and their dependence on recent dynamical history in order to understand the real impact that the cluster core has on the evolution of galaxies. We analyse the properties of more than 1000 galaxies brighter than M_r_^0.1^=-19.6 on the outskirts of 90 clusters (1<r/r_vir_<2) in the redshift range 0.05<z<0.10. Using the line of sight velocity of galaxies relative to the cluster's mean, we selected low and high velocity subsamples. Theoretical predictions indicate that a significant fraction of the first subsample should be backsplash galaxies, that is, objects that have already orbited near the cluster centre. A significant proportion of the sample of high relative velocity (HV) galaxies seems to be composed of infalling objects. Our results suggest that, at fixed stellar mass, late-type galaxies in the low-velocity (LV) sample are systematically older, redder, and have formed fewer stars during the last 3Gyrs than galaxies in the HV sample. This result is consistent with models that assume that the central regions of clusters are effective in quenching the star formation by means of processes such as ram pressure stripping or strangulation. At fixed stellar mass, LV galaxies show some evidence of having higher surface brightness and smaller size than HV galaxies. These results are consistent with the scenario where galaxies that have orbited the central regions of clusters are more likely to suffer tidal effects, producing loss of mass as well as a re-distribution of matter towards more compact configurations. Finally, we found a higher fraction of ET galaxies in the LV sample, supporting the idea that the central region of clusters of galaxies may contribute to the transformation of morphological types towards earlier types.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/2067
- Title:
- Galaxy survey data in QSO/cluster fields
- Short Name:
- J/MNRAS/475/2067
- Date:
- 02 Feb 2022 07:37:25
- Publisher:
- CDS
- Description:
- We analyse the intracluster medium (ICM) and circumgalactic medium (CGM) in seven X-ray-detected galaxy clusters using spectra of background quasi-stellar objects (QSOs) (HST-COS/STIS), optical spectroscopy of the cluster galaxies (MMT/Hectospec and SDSS), and X-ray imaging/spectroscopy (XMM-Newton and Chandra). First, we report a very low covering fraction of HI absorption in the CGM of these cluster galaxies, f_c_=_25^+25^_-15_ percent, to stringent detection limits (N(HI)<10^13^cm^-2^). As field galaxies have an HI covering fraction of ~100 per cent at similar radii, the dearth of CGM HI in our data indicates that the cluster environment has effectively stripped or overionized the gaseous haloes of these cluster galaxies. Secondly, we assess the contribution of warm-hot (10^5^-10^6^K) gas to the ICM as traced by OVI and broad Ly{alpha} (BLA) absorption. Despite the high signal-to-noise ratio of our data, we do not detect OVI in any cluster, and we only detect BLA features in the QSO spectrum probing one cluster. We estimate that the total column density of warm-hot gas along this line of sight totals to ~3 per cent of that contained in the hot T>10^7^K X-ray emitting phase. Residing at high relative velocities, these features may trace pre-shocked material outside the cluster. Comparing gaseous galaxy haloes from the low-density 'field' to galaxy groups and high-density clusters, we find that the CGM is progressively depleted of HI with increasing environmental density, and the CGM is most severely transformed in galaxy clusters. This CGM transformation may play a key role in environmental galaxy quenching.
- ID:
- ivo://CDS.VizieR/J/ApJ/798/41
- Title:
- GALEX NUV observations of bright M-type stars
- Short Name:
- J/ApJ/798/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magnetohydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lepine & Gaidos catalog (2011, J/AJ/142/138) of bright M dwarfs with the Galaxy Evolution Explorer (GALEX) catalog of NUV (1771-2831{AA}) sources. Of the 4805 sources with GALEX counterparts, 797 have NUV emission significantly (>2.5{sigma}) in excess of an empirical basal level. We inspected these candidate active stars using visible-wavelength spectra, high-resolution adaptive optics imaging, time-series photometry, and literature searches to identify cases where the elevated NUV emission is due to unresolved background sources or stellar companions; we estimated the overall occurrence of these "false positives" (FPs) as ~16%. We constructed an NUV luminosity function that accounted for FPs, detection biases of the source catalogs, and GALEX upper limits. We found the NUV luminosity function to be inconsistent with predictions from a constant star-formation rate and simplified age-activity relation defined by a two-parameter power law.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/60
- Title:
- GALEX Time Domain Survey I. UV variable sources
- Short Name:
- J/ApJ/766/60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ~40deg^2^ of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ~3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5{sigma} level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |{Delta}m|=4.6mag and 2.9mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV<23mag and |{Delta}m|>0.2mag of ~8.0, 7.7, and 1.8deg^-2^ for quasars, active galactic nuclei, and RR Lyrae stars, respectively. We also calculate a surface density rate in the UV for transient sources, using the effective survey time at the cadence appropriate to each class, of ~15 and 52deg^-2^/yr for M dwarfs and extragalactic transients, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/135
- Title:
- Gamma-ray bright blazars spectrophotometry
- Short Name:
- J/ApJ/789/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present {gamma}-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 {gamma}-ray bright blazars over 4 years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the Swift satellite, and augmented by data from the Fermi Gamma-ray Space Telescope and other publicly available data from Swift. The sample consists of 21 flat-spectrum radio quasars (FSRQs) and 12 BL Lac objects (BL Lacs). We identify quiescent and active states of the sources based on their {gamma}-ray behavior. We derive {gamma}-ray, X-ray, and optical spectral indices, {alpha}_{gamma}_, {alpha}_X_, and {alpha}_o_, respectively (F_{nu}_{prop.to}{nu}^{alpha}^), and construct spectral energy distributions during quiescent and active states. We analyze the relationships between different spectral indices, blazar classes, and activity states. We find (1) significantly steeper {gamma}-ray spectra of FSRQs than for BL Lacs during quiescent states, but a flattening of the spectra for FSRQs during active states while the BL Lacs show no significant change; (2) a small difference of {alpha}_X_ within each class between states, with BL Lac X-ray spectra significantly steeper than in FSRQs; (3) a highly peaked distribution of X-ray spectral slopes of FSRQs at ~ -0.60, but a very broad distribution of {alpha}_X_of BL Lacs during active states; (4) flattening of the optical spectra of FSRQs during quiescent states, but no statistically significant change of {alpha}_o_ of BL Lacs between states; and (5) a positive correlation between optical and {gamma}-ray spectral slopes of BL Lacs, with similar values of the slopes. We discuss the findings with respect to the relative prominence of different components of high-energy and optical emission as the flux state changes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/L6
- Title:
- Gamma-ray burst Eiso/Lopt
- Short Name:
- J/MNRAS/449/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gamma-ray burst (GRB) optical and X-ray afterglow luminosity is expected to correlate with the GRB isotropic equivalent kinetic energy of the outflow in the standard synchrotron model for GRB afterglows. Previous studies, using prompt GRB isotropic equivalent energy (E_iso_) as a proxy for isotropic equivalent kinetic energy, have generally confirmed a correlation between X-ray and optical afterglow luminosities. Assuming that GRB afterglow luminosity does not evolve strongly with redshift, we identify a strong Malmquist bias in GRB optical and X-ray afterglow luminosity data. We show that selection effects dominate the observed E_iso_-L_opt_, X correlations, and have likely been underestimated in other studies. The bias is strongest for a subset of optically faint bursts m>24 at 24h with z>2. After removing this optical selection bias, the E_iso_-L_opt_, X correlation for long GRBs is not statistically significant, but combining both long and short GRB luminosity data the correlation is significant. Using the median of the E_iso_ and L_opt_, X distributions, we apply the synchrotron model assuming the same power-law index for short and long GRBs, but different microphysical parameter distributions. Comparing the ratio of optical and X-ray luminosities, we find tentative evidence that the fraction of post-shock energy in magnetic fields, {epsilon}_B_, could be systematically higher in short GRBs compared to long GRBs.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/30
- Title:
- Gamma-ray burst flares: X-ray flaring
- Short Name:
- J/ApJ/788/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 498 flaring periods found in gamma-ray burst (GRB) light curves taken from the online Swift X-Ray Telescope GRB Catalogue (Evans et al. 2007A&A...469..379E, 2009, J/MNRAS/397/1177). We analyzed 680 individual light curves using a flare detection method developed and used on our UV/optical GRB Flare Catalog. This method makes use of the Bayesian Information Criterion to analyze the residuals of fitted GRB light curves and statistically determines the optimal fit to the light curve residuals in an attempt to identify any additional features. These features, which we classify as flares, are identified by iteratively adding additional "breaks" to the light curve. We find evidence of flaring in 326 of the analyzed light curves. For those light curves with flares, we find an average number of ~1.5 flares per GRB. As with the UV/optical, flaring in our sample is generally confined to the first 1000 s of the afterglow, but can be detected to beyond 10^5^ s. Only ~50% of the detected flares follow the "classical" definition of {Delta}t/t<=0.5, with many of the largest flares exceeding this value.
- ID:
- ivo://CDS.VizieR/J/other/RAA/13.259
- Title:
- {gamma}-ray Doppler factor for Fermi blazars
- Short Name:
- J/other/RAA/13.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations suggest that gamma-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the gamma-ray region. We compiled the X-ray observations for 138 Fermi blazars (54 flat spectrum radio quasars, 36 low-peaked BL Lacertae objects, and 48 high-peaked BL Lacertae objects) and calculated their Doppler factors, {delta}_{gamma}. It is interesting that the calculated Doppler factors, {delta}_{gamma}, are strongly correlated with the gamma-ray luminosity.
- ID:
- ivo://CDS.VizieR/J/A+A/422/941
- Title:
- Gas content in 1038 interacting galaxies
- Short Name:
- J/A+A/422/941
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A study of the gas content in 1038 interacting galaxies, essentially selected from Arp (<VII/74>), Arp and Madore (<VII/170>), Vorontsov-Velyaminov (<VII/236>) catalogues and some of the published literature, is presented here. The data on the interstellar medium have been extracted from a number of sources in the literature and compared with a sample of 1916 normal galaxies. The mean values for each of the different ISM tracers (FIR, 21cm, CO lines, X-ray) have been estimated by means of survival analysis techniques, in order to take into account the presence of upper limits.
- ID:
- ivo://CDS.VizieR/J/PASP/125/477
- Title:
- Gas Survey of Protoplanetary Systems. I.
- Short Name:
- J/PASP/125/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the ACS instrument on the Herschel Space Observatory. This Open Time Key program, known as GASPS (Gas Survey of Protoplanetary Systems), targeted ~250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63um the brightest far-infrared line in such objects. A subset of the brightest targets were also surveyed in [OI]145um, [CII] at 157um, as well as several transitions of HO and high-excitation CO lines at selected wavelengths between 78 and 180um. Additionally, GASPS included continuum photometry at 70, 100 and 160um, around the peak of the dust emission.
