- ID:
- ivo://CDS.VizieR/J/ApJ/698/819
- Title:
- MgII and LRGs cross-correlation analysis
- Short Name:
- J/ApJ/698/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the cross-correlation of MgII({lambda}2796, 2803) quasar absorption systems with luminous red galaxies (LRGs) from the Fifth Data Release (DR5) of the Sloan Digital Sky Survey. The absorption line sample consists of 2705 unambiguously intervening MgII absorption systems, detected at a 4{sigma} level, covering a redshift range (0.36<=z_abs_<=0.8) and a rest equivalent-width range of 0.8{AA}<=W^{lambda}2796^_r_<=5.0{AA}. We cross-correlate these absorbers with 1495604 LRGs with accurate photometric redshifts in the same redshift range and examine the relationship of MgII equivalent width and clustering amplitude.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/242/28
- Title:
- MgII-BAL quasar variability in SDSS spectra
- Short Name:
- J/ApJS/242/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present absorption variability results for 134 bona fide MgII broad absorption-line (BAL) quasars at 0.46<=z<=2.3 covering days to ~10yr in the rest frame. We use multiple-epoch spectra from the Sloan Digital Sky Survey, which has delivered the largest such BAL variability sample ever studied. MgII-BAL identifications and related measurements are compiled and presented in a catalog. We find a remarkable time-dependent asymmetry in the equivalent width (EW) variation from the sample, such that weakening troughs outnumber strengthening troughs, the first report of such a phenomenon in BAL variability. Our investigations of the sample further reveal that (i) the frequency of BAL variability is significantly lower (typically by a factor of 2) than that in high-ionization BALQSO samples, (ii) MgII-BAL absorbers tend to have relatively high optical depths and small covering factors along our line of sight, (iii) there is no significant EW-variability correlation between MgII troughs at different velocities in the same quasar, and (iv) the EW-variability correlation between MgII and AlIII BALs is significantly stronger than that between MgII and CIV BALs at the same velocities. These observational results can be explained by a combined transverse-motion/ionization-change scenario, where transverse motions likely dominate the strengthening BALs while ionization changes and/or other mechanisms dominate the weakening BALs.
- ID:
- ivo://CDS.VizieR/J/A+A/410/33
- Title:
- MgII/FeII absorbers in 2dF-quasar survey
- Short Name:
- J/A+A/410/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the first data release of the 2-degree Field quasar survey (Cat. <VII/223>) to investigate the effect of gravitational magnification by foreground absorbing systems on background quasars. We select two populations of quasars from this sample: one with strong MgII/FeII absorbers and one without. The selection is done in such a way that the two populations have the same redshift distribution and the absorber detection procedure discards possible biases with quasar magnitude.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/156
- Title:
- MgII/FeII absorption profile for 0.3<z<1.4 galaxies
- Short Name:
- J/ApJ/794/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze Mg II {lambda}{lambda}2796, 2803 and Fe II {lambda}{lambda}2586, 2600 absorption profiles in individual spectra of 105 galaxies at 0.3<z<1.4. The galaxies, drawn from redshift surveys of the GOODS fields and the Extended Groth Strip, sample the range in star formation rates (SFRs) occupied by the star-forming sequence with stellar masses log M_*_/M_{sun}_>~9.6 down to SFR>~2 M_{sun}_/yr at 0.3<z<0.7. Using the Doppler shifts of Mg II and Fe II absorption as tracers of cool gas kinematics, we detect large-scale winds in 66+/-5% of the galaxies. Hubble Space Telescope Advanced Camera for Surveys imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ~89% of galaxies having inclinations (i) <30{deg} (face-on), while the wind detection rate is ~45% in objects having i>50{deg} (edge-on). Combined with the comparatively weak dependence of wind detection rate on intrinsic galaxy properties, this implies that biconical outflows are ubiquitous in normal, star-forming galaxies at z~0.5. We find that wind velocity is correlated with galaxy M_*_ at 3.4{sigma} significance, while outflow equivalent width is correlated with SFR at 3.5{sigma} significance, suggesting hosts with higher SFR launch more material and/or generate a larger velocity spread for the absorbing clouds. Assuming the gas is driven into halos with isothermal density profiles, the wind velocities (~200-400 km/s) permit escape from the halo potentials only for the lowest-M_*_systems in the sample. However, the gas carries sufficient energy to reach distances >~50 kpc, and may therefore be a viable source of material for the massive, cool circumgalactic medium around bright galaxies at z~0.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/30
- Title:
- MgII line vs 3000{AA} continuum analysis in 68 QSOs
- Short Name:
- J/ApJ/843/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relationship between the MgII{lambda}2798 emission line and the 3000{AA} continuum variations using a sample of 68 intermediate-redshift (z~0.65-1.50) broad-line quasars spanning a bolometric luminosity range of 44.49erg/s<=logL_bol_<=46.31erg/s (Eddington ratio from ~0.026 to 0.862). This sample is constructed from SDSS-DR7Q and BOSS-DR12Q, each with at least two spectroscopic epochs in SDSS-I/II/III surveys. In addition, we adopt the following signal-to-noise ratio (S/N) selection criteria: (a) for MgII and the 3000{AA} continuum, S/N>=10; and (b) for narrow lines, S/N>=5. All our quasar spectra are recalibrated based on the assumption of constant narrow emission- line fluxes. In an analysis of spectrum-to-spectrum variations, we find a fairly close correlation (Spearman {rho}=0.593) between the variations in broad MgII and in the continuum. This is consistent with the idea that MgII is varying in response to the continuum emission variations. Adopting the modified weighted least squares regression method, we statistically constrain the slopes (i.e., the responsivity {alpha} of the broad MgII) between the variations in both components for the sources in different luminosity bins after eliminating intrinsic biases introduced by the rescaling process itself. It is shown that the responsivity is quite small (average {bar}{alpha}~0.464) and anti- correlates with the quasar luminosity. Our results indicate that high signal- to-noise flux measurements are required to robustly detect the intrinsic variability and the time lag of the MgII line.
- ID:
- ivo://CDS.VizieR/J/ApJS/255/28
- Title:
- ~420MHz uGMRT obs. of MIR selected radio-loud AGN
- Short Name:
- J/ApJS/255/28
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present results from a spectroscopically blind search for associated and intervening HI 21cm and OH 18cm absorption lines toward 88 active galactic nuclei (AGN) at 2<z<5 using the uGMRT. The sample of AGN with 1.4GHz spectral luminosity in the range 10^27-29.3^W/Hz is selected using mid-infrared colors and closely resembles the distribution of the underlying quasar population. The search for associated or proximate absorption, defined to be within 3000km/s of the AGN redshift, led to one HI 21cm absorption detection (M1540-1453; z_abs_=2.1139). This is only the fourth known absorption at z>2. The detection rate (1.6_-1.4_^+3.8^%) suggests a low covering factor of the cold neutral medium (CNM; T~100K) associated with these powerful AGN. The intervening absorption line search, with a sensitivity to detect the CNM in damped Ly{alpha} systems (DLAs), has comoving absorption path lengths of {Delta}X=130.1 and 167.7 for HI and OH, respectively. The corresponding number of absorbers per unit comoving path length are <=0.014 and <=0.011, respectively. The former is at least 4.5 times lower than that of DLAs and consistent with the CNM cross section estimated using H_2_ and CI absorbers at z>2. Our AGN sample is optically fainter compared to the quasars used to search for DLAs in the past. In our optical spectra obtained using SALT and NOT, we detect five intervening (redshift path ~9.3) and two proximate DLAs. This is slightly excessive compared to the statistics based on optically selected quasars. The nondetection of HI 21cm absorption from these DLAs suggests a small CNM covering fraction around galaxies at z>2.
- ID:
- ivo://CDS.VizieR/J/A+A/418/465
- Title:
- Mid-infrared and hard X-ray emission in AGN
- Short Name:
- J/A+A/418/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use mid-infrared spectral decomposition to separate the 6{mu}m mid-infrared AGN continuum from the host emission in the ISO low resolution spectra of 71 active galaxies and compare the results to observed and intrinsic 2-10keV hard X-ray fluxes from the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3075
- Title:
- Mid-infrared population of ELAIS-S1 sample
- Short Name:
- J/AJ/127/3075
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength catalog (15{mu}m, R-band, K-band, and 1.4GHz flux) plus spectroscopic identifications for 406 15{mu}m sources detected in the European Large Area ISO Survey (ELAIS) region S1, over the flux density range 0.5<S15{mu}m<150mJy. Three hundred thirty-two (~82%) sources are optically identified down to R~23.0. Spectra or bona fide stellar identifications are obtained for 290 objects (~88% of the optically identified sources). The areal coverage, mid-infrared (MIR) and optical completeness of the sample are discussed in order to allow statistical and evolutionary analyses.
- ID:
- ivo://CDS.VizieR/J/ApJ/800/80
- Title:
- MIR properties of galaxies in A2199 at z~0.03
- Short Name:
- J/ApJ/800/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the mid-infrared (MIR) properties of the galaxies in the A2199 supercluster at z=0.03 to understand the star formation activity of galaxy groups and clusters in the supercluster environment. Using the Wide-field Infrared Survey Explorer (WISE) data, we find no dependence of mass-normalized integrated star formation rates of galaxy groups/clusters on their virial masses. We classify the supercluster galaxies into three classes in the MIR color-luminosity diagram: MIR blue cloud (massive, quiescent, and mostly early-type), MIR star-forming sequence (mostly late-type), and MIR green valley galaxies. These MIR green valley galaxies are distinguishable from the optical green valley galaxies in the sense that they belong to the optical red sequence. We find that the fraction of each MIR class does not depend on the virial mass of each group/cluster. We compare the cumulative distributions of surface galaxy number density and cluster/group-centric distance for the three MIR classes. MIR green valley galaxies show the distribution between MIR blue cloud and MIR star-forming (SF) sequence galaxies. However, if we fix galaxy morphology, early- and late-type MIR green valley galaxies show different distributions. Our results suggest a possible evolutionary scenario of these galaxies: (1) late-type MIR SF sequence galaxies --> (2) late-type MIR green valley galaxies --> (3) early-type MIR green valley galaxies --> (4) early-type MIR blue cloud galaxies. In this sequence, the star formation of galaxies is quenched before the galaxies enter the MIR green valley, and then morphological transformation occurs in the MIR green valley.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/33
- Title:
- MIR reverberation mapping analysis of 87 z<0.5 PG AGNs
- Short Name:
- J/ApJ/886/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The continued operation of the Wide-field Infrared Survey Explorer (WISE), combined with several ground-based optical transient surveys (e.g., CRTS, ASAS-SN, and PTF), offers an unprecedented opportunity to explore the dust structures in luminous active galactic nuclei (AGNs). We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at z<~0.5. To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these data sets and retrieve the dust RM signals have been developed. We find that ~70% of the sample (with a completeness correction up to 95%) has convincing mid-IR time lags in the WISE W1 (~3.4{mu}m) and W2 (~4.5{mu}m) bands, and they are proportional to the square root of the AGN luminosity. Combined with previous K-band (~2.2{mu}m) RM results in the literature, the inferred dust emission size ratios are R_K_:R_W1_:R_W2_=0.6:1:1.2. Under simple assumptions, we put preliminary constraints on the projected dust surface density at these bands and reveal the possibly different torus structures among hot-dust-deficient, warm-dust-deficient, and normal quasars from the reverberation signals. With multi-epoch Spitzer data and later WISE photometry, we also explore AGN IR variability at 10-24{mu}m over a 5yr timescale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24{mu}m of no more than 10% of that in the W1 band, indicating that the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24{mu}m variability, consistent with the unification picture of radio-loud AGNs.
