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Start Over Subject quasars Validation Level 2
451. Luminous WISE-selected quasars in SDSS Stripe 82
ID:
ivo://CDS.VizieR/J/ApJ/861/37
Title:
Luminous WISE-selected quasars in SDSS Stripe 82
Short Name:
J/ApJ/861/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopically complete sample of 147 infrared-color-selected active galactic nuclei (AGNs) down to a 22{mu}m flux limit of 20mJy over the ~270deg^2^ of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (Lbol>~10^12^L_{sun}_) and are found out to z~3. We classify the AGNs into three types, finding 57 blue, unobscured Type-1 (broad-lined) sources; 69 obscured, Type-2 (narrow-lined) sources; and 21 moderately reddened Type-1 sources (broad-lined and E(B-V)>0.25). We study a subset of this sample in X-rays and analyze their obscuration to find that our spectroscopic classifications are in broad agreement with low, moderate, and large amounts of absorption for Type-1, red Type-1, and Type-2 AGNs, respectively. We also investigate how their X-ray luminosities correlate with other known bolometric luminosity indicators such as [OIII] line luminosity (L[OIII]) and infrared luminosity (L6{mu}m). While the X-ray correlation with L[OIII] is consistent with previous findings, the most infrared-luminous sources appear to deviate from established relations such that they are either underluminous in X-rays or overluminous in the infrared. Finally, we examine the luminosity function evolution of our sample, and by AGN type, in combination with the complementary, infrared-selected, AGN sample of Lacy et al. (2013), spanning over two orders of magnitude in luminosity. We find that the two obscured populations evolve differently, with reddened Type-1 AGNs dominating the obscured AGN fraction (~30%) for L_5{mu}m_>10^45^erg/s, while the fraction of Type-2 AGNs with L_5{mu}m_<10^45^erg/s rises sharply from 40% to 80% of the overall AGN population.
452. Ly{alpha} absorption systems. V.
ID:
ivo://CDS.VizieR/J/ApJ/559/654
Title:
Ly{alpha} absorption systems. V.
Short Name:
J/ApJ/559/654
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a program to obtain and analyze HST WFPC2 images and ground-based images of galaxies identified in an imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. Here we present the additional HST WFPC2 observations of galaxies in 10 QSO fields that were not included in Paper I (Chen et al., 1998, Cat. <J/ApJ/498/77>) and near-infrared imaging observations of galaxies in 15 QSO fields.
453. Ly{alpha} and OVI in galaxies around quasars
ID:
ivo://CDS.VizieR/J/ApJ/740/91
Title:
Ly{alpha} and OVI in galaxies around quasars
Short Name:
J/ApJ/740/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the association of galaxies with Ly{alpha} and OVI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z_em_=0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho}=300h^-1^_72_kpc: 33/37 of our L>0.01L* galaxies show Ly{alpha} equivalent width W^Ly{alpha}^>=50 m{AA}. Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at ~10^10.5^+/-0.3M_{sun}_ for a constant N_H_=10^19^cm^-2^. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W^Ly{alpha}^>300m{AA}) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W^Ly{alpha}^=30-300m{AA} occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of ~400h^-1^_72_kpc. Regarding OVI, we observe a near unity covering fraction to {rho}=200h^-1^_72_kpc for L>0.1L* galaxies and to {rho}=300h^-1^_72_kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our Ly{alpha} results, stronger OVI systems (W^1031^>70m{AA}) arise in the virialized halos of L>0.1L* galaxies. Unlike Ly{alpha}, the weaker OVI systems (W^1031^~30m{AA}) arise in the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L~0.3L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.
454. Ly{alpha} candidates from a MUSE survey of 6 AGNs
ID:
ivo://CDS.VizieR/J/ApJ/859/53
Title:
Ly{alpha} candidates from a MUSE survey of 6 AGNs
Short Name:
J/ApJ/859/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z>3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly{alpha} sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly{alpha} luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240{AA} that are the best candidates for dark galaxies in our survey at z>3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z~2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t=60Myr on the quasar lifetime.
455. Ly{alpha} forest power spectrum at 1.8<=z<=3.4
ID:
ivo://CDS.VizieR/J/ApJ/852/22
Title:
Ly{alpha} forest power spectrum at 1.8<=z<=3.4
Short Name:
J/ApJ/852/22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new measurement of the Ly{alpha} forest power spectrum at 1.8<z<3.4 using 74 Keck/HIRES and VLT/UVES high-resolution, high-signal-to-noise-ratio quasar spectra. We developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped Ly{alpha} absorption systems, and metal absorption lines. Our measurement results in unprecedented precision on the small-scale modes k>0.02s/km, inaccessible to previous SDSS/BOSS analyses. It is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. We quantify the effect of metals on the small- scale power and find a modest effect on modes with k<0.1s/km. As a result, by masking metals and restricting to k<0.1s/km, their impact is completely mitigated. We present an end-to-end Bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from Ly{alpha} forest simulations. These mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform Markov chain Monte Carlo fits. Our results agree well with BOSS on scales k<0.02s/km, where the measurements overlap. The combination of the percent-level low-k precision of BOSS with our 5%-15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter.
456. Ly-Alpha Forest spectra simulation analysis. I.
ID:
ivo://CDS.VizieR/J/ApJ/457/102
Title:
Ly-Alpha Forest spectra simulation analysis. I.
Short Name:
J/ApJ/457/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present moderate-resolution (~50km/s FWHM) spectra of the Ly-alpha forest for seven quasars with redshifts ranging from 2.53 to 3.13, obtained with the Blue Spectrograph and photon-counting Reticon at the Multiple Mirror Telescope. Combined with spectra of 10 other quasars presented elsewhere, we have characterized the distribution of cloud properties in a way which was designed to minimize any subjective part of the analysis. We used artificial absorption spectra, with the same resolution, sampling and signal-to-noise ratio as a function of wavelength as the actual data. Distributions of the physical parameters of the Ly-alpha clouds, namely, the neutral hydrogen column density (N) and Doppler parameter (b), were approximated with d"N"/dN proportional to N^(-beta) and d"N"/db proportional to exp[-(b-<b>)^2/(2 sigma_b^2)], respectively. We constructed a grid of simulated spectra with different input parameters. Comparison of properties of the simulated spectra with the observed spectra yielded acceptable ranges of parameters. Our technique differs from previous similar work in that we use the information contained in the distribution of the strength of the absorption in each resolution element and the distribution of separations between absorption complexes. We derive beta =1.4+/-0.1 for N ranging from 10^13 to 10^16cm^-2 and <b>=30+/-15km/s. Most previous studies based on line lists indicated beta=1.7-1.9. We attribute this difference to flattening of the column density distribution for low N, recently confirmed by higher resolution observations. Our result for <b>, though consistent with values quoted in the literature, is of lower significance, since it is less than the resolution of our spectra. We conclude by commenting on the importance of line blending in data sets of this kind.
457. Lyman alpha absorbers in 0.5<z<1.9 QSOs
ID:
ivo://CDS.VizieR/J/A+A/458/427
Title:
Lyman alpha absorbers in 0.5<z<1.9 QSOs
Short Name:
J/A+A/458/427
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the evolution and the statistical properties of the Ly{alpha} absorbers of the intergalactic medium (IGM) in the largely unexplored redshift range z=0.5-1.9. We use high-resolution (R>=30000) UV (STIS) and optical (VLT/UVES and Keck/HIRES) spectra of nine bright quasars with z_em_<1.94. The Ly{alpha} lines detected in the lines of sight (LOS) towards these quasars are evaluated with a software package which determines simultaneously the quasar continuum and the line profiles.
458. Lyman{alpha} emitting galaxies at z=2.38
ID:
ivo://CDS.VizieR/J/ApJ/614/75
Title:
Lyman{alpha} emitting galaxies at z=2.38
Short Name:
J/ApJ/614/75
Date:
21 Oct 2021
Publisher:
CDS
Description:
In Paper 1 (Palunas et al., 2004ApJ...602..545P) of this series we identified an 80 comoving Mpc filament of candidate Ly{alpha}-emitting galaxies at redshift 2.38. In this paper we present spectroscopy of the 37 galaxy candidates. Our spectroscopy reached a surface brightness limit of 5.0x10^-17^erg/cm^2^/s/arcsec^2^. Of the 14 candidates down to this limit, 12 were confirmed to be Ly{alpha}-emitting galaxies at the filament redshift. We also obtained spectral confirmation for six of the lower surface brightness candidates, all of which also lay at the filament redshift. In addition, we identify a foreground cluster of QSOs at z=1.65.
459. Lyman alpha forest in HE 0515-4414
ID:
ivo://CDS.VizieR/J/A+A/391/L11
Title:
Lyman alpha forest in HE 0515-4414
Short Name:
J/A+A/391/L11
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigated HST/STIS and VLT/UVES spectra of the bright QSO HE 0515-4414 (z_em_=1.73, B=15.0) to study the Lyman alpha forest in the redshift range 0.9 < z < 1.7 at a resolution <10km/s.
460. Lyman{alpha} forest in QSO pairs
ID:
ivo://CDS.VizieR/J/MNRAS/391/1457
Title:
Lyman{alpha} forest in QSO pairs
Short Name:
J/MNRAS/391/1457
Date:
21 Oct 2021
Publisher:
CDS
Description:
We look for signs of the HI transverse proximity effect in the spectra of 130 quasi-stellar object (QSO) pairs, most with transverse separations in the plane of the sky of 0.1-3Mpc at z~2.2. We expected to see a decrease in Ly{alpha} forest HI absorption in the spectrum of background QSOs near the position of foreground QSOs. Instead, we see no change in the absorption in front of the foreground QSOs, and we see evidence for a 50 per cent increase in the absorption out to 6Mpc behind the foreground QSOs. Further, we see no change in the HI absorption along the line-of-sight to the foreground QSOs, the normal line-of-sight proximity effect. We may account for the lack of change in the HI absorption if the effect of extra ultraviolet photons is cancelled by higher gas density around QSOs. If so, the increase in absorption behind the QSOs then suggests that the higher gas density there is not cancelled by the UV radiation from the QSOs. We can explain our observations if QSOs have had their current UV luminosities for less than approximately a million years, a time-scale that has been suggested for accretion disc instabilities and gas depletion.

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