Abstract
We adopt and analyse results on the incidence and physical properties of damped Ly α systems (DLAs) to predict the astrophysical impact of gas in galaxies on observations of fast radio ...bursts (FRBs). Three DLA measures form the basis of this analysis: (i) the H i column density distribution, parametrized as a double power-law; (ii) the incidence of DLAs with redshift (derived here), $\ell _{\rm DLA}(z)=A+B \, \arctan (z-C)$ with $A=0.236_{-0.021}^{+0.016},B=0.168_{-0.017}^{+0.010}$ and $C=2.87_{-0.13}^{+0.17}$; and (iii) the electron density, parametrized
as a log-normal deviate with mean 10−2.6cm−3 and dispersion 0.3 dex. Synthesizing these results, we estimate that the average rest-frame dispersion measure (DM)
from the neutral medium of a single, intersecting galaxy is ${\rm DM}^{\rm NM}_{\rm DLA}=0.25 \, {\rm pc \, cm^{-3}}$. Analysis of Al iii and C ii* absorption limits the putative warm ionized medium to contribute ${\rm DM}^{\rm WIM}_{\rm DLA}<20\, {\rm pc \, cm^{-3}}$. Given the low incidence of DLAs, we find that a population of FRBs at z = 2 will incur $\overline{\rm DM}^{\rm NM}_{\rm DLA}(z_{\rm FRB}={2})=0.01\, {\rm pc \, cm^{-3}}$ on average, with a 99 per cent confidence level upper bound of 0.22 pc cm−3. Assuming that turbulence of the interstellar medium (ISM) in external galaxies is qualitatively similar to our Galaxy, we estimate that the angular broadening of an FRB by intersecting galaxies is negligible (θscatt < 0.1 mas). The temporal broadening is also predicted to be small, τDLA ≈ 0.3 ms for a z = 1 galaxy intersecting a z = 2 FRB for an observing frequency of ν = 1 GHz. Even with ν = 600 MHz, the fraction of sightlines broadened beyond 25 ms is only approximately 0.1 per cent. We conclude that gas within the ISM of intervening galaxies has a minor effect on the detection of FRBs and their resultant DM distributions. Download the repository at https://github.com/FRBs/FRB to repeat and extend the calculations presented here.
THE FUNDAMENTAL PLANE OF DAMPED Lyα SYSTEMS Neeleman, Marcel; Wolfe, Arthur M.; Prochaska, J. Xavier ...
Astrophysical journal/The Astrophysical journal,
05/2013, Volume:
769, Issue:
1
Journal Article
We examine the kinematic structure of damped Lyman α systems (DLAs) in a series of cosmological hydrodynamic simulations using the arepo code. We are able to match the distribution of velocity ...widths of associated low-ionization metal absorbers substantially better than earlier work. Our simulations produce a population of DLAs dominated by haloes with virial velocities around 70 km s−1, consistent with a picture of relatively small, faint objects. In addition, we reproduce the observed correlation between velocity width and metallicity and the equivalent width distribution of Si ii. Some discrepancies of moderate statistical significance remain; too many of our spectra show absorption concentrated at the edge of the profile and there are slight differences in the exact shape of the velocity width distribution. We show that the improvement over previous work is mostly due to our strong feedback from star formation and our detailed modelling of the metal ionization state.
Ly Halos around z ∼ 6 Quasars Drake, Alyssa B.; Farina, Emanuele Paolo; Neeleman, Marcel ...
The Astrophysical journal,
08/2019, Volume:
881, Issue:
2
Journal Article
Peer reviewed
We present deep MUSE observations of five quasars within the first Gyr of the universe (z 6), four of which display extended Ly halos. After PSF subtraction, we reveal halos surrounding two quasars ...for the first time, as well as confirm the presence of two more halos for which tentative detections exist in long-slit spectroscopic observations and narrowband imaging. The four Ly halos presented here are diverse in morphology and size, they each display spatial asymmetry, and none are centered on the position of the quasar. Spectra of the diffuse halos demonstrate that none are dramatically offset in velocity from the systemic redshift of the quasars (Δv < 200 km s−1); however. each halo shows a broad Ly line, with a velocity width ∼1000 km s−1. Total Ly luminosities range between ∼2 × 1043 and ∼2 × 1044 erg s−1, reaching maximum radial extents of 13-30 pkpc from the quasar positions. We find larger sizes and higher Ly luminosities than previous literature results at this redshift, but find no correlation between the quasar properties and the Ly halo, suggesting that the detected emission is most closely related to the physical properties of the circumgalactic medium.
We present evidence that the cosmological mean metallicity of neutral atomic hydrogen gas shows a sudden decrease at z > 4.7 down to (ProQuest: Formulae and/or non-USASCII text omitted) which is ...6sigma deviant from that predicted by a linear fit to the data at lower redshifts. This measurement is made possible by the chemical abundance measurements of eight new damped Ly alpha (DLA) systems at z > 4.7 observed with the Echellette Spectrograph and Imager on the Keck II Telescope, doubling the number of measurements at z > 4.7 to 16. Possible explanations for this sudden decrease in metallicity include a change in the physical processes that enrich the neutral gas within disks, or an increase of the covering factor of neutral gas outside disks due to a lower ultraviolet radiation field and higher density at high redshift. The later possibility would result in a new population of presumably lower metallicity DLAs, with an increased contribution to the DLA population at higher redshifts resulting in a reduced mean metallicity. Furthermore, we provide evidence of a possible decrease at z > 4.7 in the comoving metal mass density of DLAs, rho sub(metals) (z) sub(DLA), which is flat out to z ~ 4.3. Such a decrease is expected, as otherwise most of the metals from star-forming galaxies would reside in DLAs by z ~ 6. While the metallicity is decreasing at high redshift, the contribution of DLAs to the total metal budget of the universe increases with redshift, with DLAs at z ~ 4.3 accounting for ~20% as many metals as produced by Lyman break galaxies.
ABSTRACT
The James Webb Space Telescope will have the power to characterize high-redshift quasars at z ≥ 6 with an unprecedented depth and spatial resolution. While the brightest quasars at such ...redshift (i.e. with bolometric luminosity $L_{\rm bol}\geqslant 10^{46}\, \rm erg/s$) provide us with key information on the most extreme objects in the Universe, measuring the black hole (BH) mass and Eddington ratios of fainter quasars with $L_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$ opens a path to understand the build-up of more normal BHs at z ≥ 6. In this paper, we show that the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA large-scale cosmological simulations do not agree on whether BHs at z ≥ 4 are overmassive or undermassive at fixed galaxy stellar mass with respect to the MBH − M⋆ scaling relation at z = 0 (BH mass offsets). Our conclusions are unchanged when using the local scaling relation produced by each simulation or empirical relations. We find that the BH mass offsets of the simulated faint quasar population at z ≥ 4, unlike those of bright quasars, represent the BH mass offsets of the entire BH population, for all the simulations. Thus, a population of faint quasars with $L_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$ observed by JWST can provide key constraints on the assembly of BHs at high redshift. Moreover, this will help constraining the high-redshift regime of cosmological simulations, including BH seeding, early growth, and co-evolution with the host galaxies. Our results also motivate the need for simulations of larger cosmological volumes down to z ∼ 6, with the same diversity of subgrid physics, in order to gain statistics on the most extreme objects at high redshift.
Gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and ...characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. Using the Atacama Large Millimeter/Submillimeter Array, we report on detections of C ii 158-μm line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of z ~ 4. Our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies.
Abstract
The discovery of quasars a few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. Quasars' ...luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of
M
BH
> 10
9
M
⊙
by
z
∼ 6. Simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. To understand which environments are able to sustain the rapid formation of these extreme sources, we started a Very Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) effort aimed at characterizing the surroundings of a sample of 5.7 <
z
< 6.6 quasars, which we have dubbed the Reionization Epoch QUasar InvEstigation with MUSE (REQUIEM) survey. We here present results of our searches for extended Ly
α
halos around the first 31 targets observed as part of this program. Reaching 5
σ
surface brightness limits of 0.1–1.1 × 10
−17
erg s
−1
cm
−2
arcsec
−2
over a 1 arcsec
2
aperture, we were able to unveil the presence of 12 Ly
α
nebulae, eight of which are newly discovered. The detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8 × 10
42
to 2 × 10
44
erg s
−1
, FWHMs between 300 and 1700 km s
−1
, sizes <30 pkpc, and redshifts consistent with those of the quasar host galaxies. As the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the REQUIEM survey enables the study of the evolution of the cool gas surrounding quasars in the first 3 Gyr of the universe. A comparison with the extended Ly
α
emission observed around bright (
M
1450
≲ −25 mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from
z
∼ 6 to
z
∼ 3, followed by a decline in the average surface brightness down to
z
∼ 2.
We combine the recent determination of the evolution of the cosmic density of molecular gas (H2) using deep, volumetric surveys, with previous estimates of the cosmic density of stellar mass, star ...formation rate and atomic gas (H i), to constrain the evolution of baryons associated with galaxies averaged over cosmic time and space. The cosmic H i and H2 densities are roughly equal at z ∼ 1.5. The H2 density then decreases by a factor \({6}_{-2}^{+3}\) to today’s value, whereas the H i density stays approximately constant. The stellar mass density is increasing continuously with time and surpasses that of the total gas density (H i and H2) at redshift z ∼ 1.5. The growth in stellar mass cannot be accounted for by the decrease in cosmic H2 density, necessitating significant accretion of additional gas onto galaxies. With the new H2 constraints, we postulate and put observational constraints on a two-step gas accretion process: (i) a net infall of ionized gas from the intergalactic/circumgalactic medium to refuel the extended H i reservoirs, and (ii) a net inflow of H i and subsequent conversion to H2 in the galaxy centers. Both the infall and inflow rate densities have decreased by almost an order of magnitude since z ∼ 2. Assuming that the current trends continue, the cosmic molecular gas density will further decrease by about a factor of two over the next 5 Gyr, the stellar mass will increase by approximately 10%, and cosmic star formation activity will decline steadily toward zero, as the gas infall and accretion shut down.
We present deep Chandra observations of PSO J231.6576−20.8335, a quasar at redshift z = 6.59 with a nearby (∼8 proper kpc) companion galaxy. The Atacama Large Millimeter/submillimeter Array observed ...both the quasar and companion to be bright in C ii, and the system has significant extended Ly emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of , power-law index of ), which results in a rest-frame X-ray luminosity comparable to other bright quasars ( ) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of Γ-potentially related to observed ongoing Eddington accretion-thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum (Γ ∼ 2) but is therefore less X-ray luminous ( ).
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