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Register a new userEvolution of CIV Absorbers. II.~Where does CIV live?
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We use the observed cumulative statistics of CIV absorbers and dark matter halos to infer the distribution of CIV-absorbing gas relative to galaxies at redshifts $0!leq!z!leq!5$. We compare the cosmic incidence $dN/dX$ of CIV absorber populations and galaxy halos, finding that massive $L geq L_{star}$ halos alone cannot account for all the observed $W_r geq 0.05$~{AA} absorbers. However, the $dN/dX$ of lower mass halos exceeds that of $W_r geq 0.05$~{AA} absorbers. We also estimate the characteristic gas radius of absorbing structures required for the observed CIV $dN/dX$, assuming each absorber is associated with a single galaxy halo. The $W_r geq 0.3$~{AA} and $W_r geq 0.6$~{AA} CIV gas radii are $sim30-70%$ ($sim20-40%$) of the virial radius of $L_{star}$ ($0.1L_{star}$) galaxies, and the $W_r geq 0.05$~{AA} gas radius is $sim100-150%$($sim60-100%$) of the virial radius of $L_{star}$ ($0.1L_{star}$) galaxies. For stronger absorbers, the gas radius relative to virial radius rises across Cosmic Noon and falls afterwards, while for weaker absorbers, the relative gas radius declines across Cosmic Noon and then dramatically rises at $z!<!1$. A strong luminosity-dependence of gas radius implies highly extended CIV envelopes around massive galaxies before Cosmic Noon, while a luminosity-independent gas radius implies highly extended envelopes around dwarf galaxies after Cosmic Noon. From available absorber-galaxy and CIV evolution data, we favor a scenario in which low-mass galaxies enrich the volume around massive galaxies at early epochs and propose that the outer halo gas ($>0.5R_v$) was produced primarily in ancient satellite dwarf galaxy outflows, while the inner halo gas ($<0.5R_v$) originated from the central galaxy and persists as recycled accreting gas.
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We report on a survey for narrow (FWHM < 600 km/s) CIV absorption lines in a sample of bright quasars at redshifts $1.8 le z < 2.25$ in the Sloan Digital Sky Survey. Our main goal is to understand the relationship of narrow CIV absorbers to quasar outflows and, more generally, to quasar environments. We determine velocity zero-points using the broad MgII emission line, and then measure the absorbers quasar-frame velocity distribution. We examine the distribution of lines arising in quasar outflows by subtracting model fits to the contributions from cosmologically intervening absorbers and absorption due to the quasar host galaxy or cluster environment. We find a substantial number ($ge 43pm6$ per cent) of absorbers with REW $> 0.3$ AA in the velocity range +750 km/s $la v la $ +12000 km/s are intrinsic to the AGN outflow. This `outflow fraction peaks near $v=+2000$ km/s with a value of $f_{outflow} simeq 0.81 pm 0.13$. At velocities below $v approx +2000$ km/s the incidence of outflowing systems drops, possibly due to geometric effects or to the over-ionization of gas that is nearer the accretion disk. Furthermore, we find that outflow-absorbers are on average broader and stronger than cosmologically-intervening systems. Finally, we find that $sim 14$ per cent of the quasars in our sample exhibit narrow, outflowing CIV absorption with REW $> 0.3$AA, slightly larger than that for broad absorption line systems.
Broad emission lines in quasars enable us to resolve structure and kinematics of the broad line emitting region (BLR) thought to in- volve an accretion disk feeding a supermassive black hole. Interpretation of broad line measures within the 4DE1 formalism simplifies the apparent confusion among such data by contrasting and unifying properties of so-called high and low accreting Population A and B sources. H{beta} serves as an estimator of black hole mass, Eddington ratio and source rest frame, the latter a valuable input for Civ{lambda}1549 studies which allow us to isolate the blueshifted wind component. Optical and HST-UV spectra yield H{beta} and Civ{lambda}1549 spectra for low-luminosity sources while VLT-ISAAC and FORS and TNG-LRS provide spectra for high Luminosity sources. New high S/N data for Civ in high-luminosity quasars are presented here for comparison with the other previously published data. Comparison of H{beta} and Civ{lambda}1549 profile widths/shifts indicates that much of the emission from the two lines arise in regions with different structure and kinematics. Covering a wide range of luminosity and redshift shows evidence for a correlation between Civ{lambda}1549 blueshift and source Eddington ratio, with a weaker trend with source luminosity (similar amplitude outflows are seen over 4 of the 5 dex luminosity range in our combined samples). At low luminosity (z < 0.7) only Population A sources show evidence for a significant outflow while at high luminosity the outflow signature begins to appear in Population B quasars as well.
Using a sample of 30,000 quasars from SDSS-DR7, we explore the range of properties exhibited by high-ionization, broad emission lines, such as CIV 1549. Specifically we investigate the anti-correlation between L_UV and emission line EQW (the Baldwin Effect) and the blueshifting of high-ionization emission lines. The blueshift of the CIV emission line is nearly ubiquitous, with a mean shift of 810 km/s for radio-quiet (RQ) quasars and 360 km/s for radio-loud (RL) quasars, and the Baldwin Effect is present in both RQ and RL samples. Composite spectra are constructed as a function of CIV emission line properties in attempt to reveal empirical relationships between different line species and the SED. Within a two-component disk+wind model of the broad emission line region (BELR), where the wind filters the continuum seen by the disk component, we find that RL quasars are consistent with being dominated by the disk component, while BALQSOs are consistent with being dominated by the wind component. Some RQ objects have emission line features similar to RL quasars; they may simply have insufficient black hole (BH) spin to form radio jets. Our results suggest that there could be significant systematic errors in the determination of L_bol and BH mass that make it difficult to place these findings in a more physical context. However, it is possible to classify quasars in a paradigm where the diversity of BELR parameters are due to differences in an accretion disk wind between quasars (and over time); these differences are underlain primarily by the SED, which ultimately must be tied to BH mass and accretion rate.
For the sample from Ge et al. of 87 low-$z$ Palomar--Green (PG) quasi-stellar objects (QSOs) and 130 high-$z$ QSOs ($0<z<5$) with $hb$-based single-epoch supermassive black hole (SMBH) masses, we performed a uniform decomposition of the civ $lambda$1549 broad-line profile. Based on the rest frame defined by the oiii $lambda$5007 narrow emission line, a medium-strong positive correlation is found between the civ blueshift and the luminosity at 5100AA or the Eddington ratio leddR. A medium-strong negative relationship is found between the civ blueshift and civ equivalent width. These results support the postulation where the radiation pressure may be the driver of civ blueshift. There is a medium strong correlation between the mass ratio of civ-based to $hb$-based mbh and the civ blueshift, which indicates that the bias for civ-based mbh is affected by the civ profile.
We have vastly increased the CIV statistics at intermediate redshift by surveying the thousands of quasars in the Sloan Digital Sky Survey Data-Release 7. We visually verified over 16,000 CIV systems with 1.46 < z < 4.55---a sample size that renders Poisson error negligible. Detailed Monte Carlo simulations show we are approximately 50% complete down to rest equivalent widths W_r ~ 0.6 AA. We analyzed the sample as a whole and in ten small redshift bins with approximately 1500 doublets each. The equivalent width frequency distributions f(W_r) were well modeled by an exponential, with little evolution in shape. In contrast with previous studies that modeled the frequency distribution as a single power law, the fitted exponential gives a finite mass density for the CIV ions. The co-moving line density dN_CIV/dX evolved smoothly with redshift, increasing by a factor of 2.37+/-0.09 from z = 4.55 to 1.96, then plateauing at dN_CIV/dX ~ 0.34 for z = 1.96 to 1.46. Comparing our SDSS sample with z < 1 (ultraviolet) and z > 5 (infrared) surveys, we see an approximately 10-fold increase in dN_CIV/dX over z ~ 6 --> 0, for W_r >= 0.6 AA. This suggests a monotonic and significant increase in the enrichment of gas outside galaxies over the 12 Gyr lifetime of the universe.
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