State-of-the-art models of massive black hole formation postulate that quasars at z > 6 reside in extreme peaks of the cosmic density structure in the early universe. Even so, direct observational ...evidence of these overdensities is elusive, especially on large scales (≫1 Mpc) as the spectroscopic follow-up of z > 6 galaxies is observationally expensive. Here we present Keck/DEIMOS optical and IRAM/NOEMA millimeter spectroscopy of a z ∼ 6 Lyman-break galaxy candidate originally discovered via broadband selection, at a projected separation of 4.65 physical Mpc (13.94 arcmin) from the luminous z = 6.308 quasar J1030+0524. This well-studied field presents the strongest indication to date of a large-scale overdensity around a z > 6 quasar. The Keck observations suggest a z ∼ 6.3 dropout identification of the galaxy. The NOEMA 1.2 mm spectrum shows a 3.5σ line that, if interpreted as C II, would place the galaxy at z = 6.318 (i.e., at a line-of-sight separation of 3.9 comoving Mpc assuming that relative proper motion is negligible). The measured C II luminosity is 3 × 108 L⊙, in line with expectations for a galaxy with a star formation rate ∼15 M⊙ yr−1, as inferred from the rest-frame UV photometry. Our combined observations place the galaxy at the same redshift as the quasar, thus strengthening the overdensity scenario for this z > 6 quasar. This pilot experiment demonstrates the power of millimeter-wavelength observations in the characterization of the environment of early quasars.
We present JWST/NIRSpec integral field data of the quasar PJ308-21 at z = 6.2342. As shown by previous ALMA and HST imaging, the quasar has two companion sources, interacting with the quasar host ...galaxy. The high-resolution G395H/290LP NIRSpec spectrum covers the 2.87 − 5.27 μm wavelength range and shows the rest-frame optical emission of the quasar with exquisite quality (signal-to-noise ratio ∼100 − 400 per spectral element). Based on the H β line from the broad line region, we obtain an estimate of the black hole mass M BH, H β ∼ 2.7 × 10 9 M ⊙ . This value is within a factor ≲1.5 of the H α -based black hole mass from the same spectrum ( M BH, H α ∼ 1.93 × 10 9 M ⊙ ) and is consistent with a previous estimate relying on the Mg II λ 2799 line ( M BH, MgII ∼ 2.65 × 10 9 M ⊙ ). All these M BH estimates are within the ∼0.5 dex intrinsic scatter of the adopted mass calibrations. The high Eddington ratio of PJ308-21 λ Edd, H β ∼ 0.67 ( λ Edd, H α ∼ 0.96) is in line with the overall quasar population at z ≳ 6. The relative strengths of the O III , Fe II , and H β lines are consistent with the empirical “Eigenvector 1” correlations as observed for low redshift quasars. We find evidence for blueshifted O III λ 5007 emission with a velocity offset Δ v O III = −1922 ± 39 km s −1 from the systemic velocity and a full width at half maximum (FWHM) FWHM (O III ) = 2776 −74 +75 km s −1 . This may be the signature of outflowing gas from the nuclear region, despite the true values of Δ v O III and FWHM (O III ) likely being more uncertain due to the blending with H β and Fe II lines. Our study demonstrates the unique capabilities of NIRSpec in capturing quasar spectra at cosmic dawn and studying their properties in unprecedented detail.
WISE J224607.6--052634.9 (W2246--0526) is a hot dust-obscured galaxy at $z$ = 4.601, and the most luminous obscured quasar known to date. W2246--0526 harbors a heavily obscured supermassive black ...hole that is most likely accreting above the Eddington limit. We present observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in seven bands, including band 10, of the brightest far-infrared (FIR) fine-structure emission lines of this galaxy: OI m OIII m NII m OI m CII m NII m CI m $, and CI m $. A comparison of the data to a large grid of Cloudy radiative transfer models reveals that a high hydrogen density ($n_ H $) and extinction ($A_ V mag), together with extreme ionization ($log(U)=-0.5$) and a high X-ray to UV ratio ($ ox are required to reproduce the observed nuclear line ratios. The values of $ ox $ and $U$ are among the largest found in the literature and imply the existence of an X-ray-dominated region (XDR). In fact, this component explains the a priori very surprising non-detection of the OIII m $ emission line, which is actually suppressed, instead of boosted, in XDR environments. Interestingly, the best-fitted model implies higher X-ray emission and lower CO content than what is detected observationally, suggesting the presence of a molecular gas component that should be further obscuring the X-ray emission over larger spatial scales than the central region that is being modeled. These results highlight the need for multiline infrared observations to characterize the multiphase gas in high redshift quasars and, in particular, W2246--0526 serves as an extreme benchmark for comparisons of interstellar medium conditions with other quasar populations at cosmic noon and beyond.
Our knowledge of galaxy formation and evolution has incredibly progressed through multi-wavelength observational constraints of the interstellar medium (ISM) of galaxies at all cosmic epochs. ...However, little is known about the physical properties of the more diffuse and lower surface brightness reservoir of gas and dust that extends beyond ISM scales and fills dark matter haloes of galaxies up to their virial radii, the circumgalactic medium (CGM). New theoretical studies increasingly stress the relevance of the latter for understanding the feedback and feeding mechanisms that shape galaxies across cosmic times, whose cumulative effects leave clear imprints into the CGM. Recent studies are showing that a – so far unconstrained – fraction of the CGM mass may reside in the cold ( T < 10 4 K) molecular and atomic phase, especially in high-redshift dense environments. These gas phases, together with the warmer ionised phase, can be studied in galaxies from z ∼ 0 to z ∼ 10 through bright far-infrared and sub-millimeter emission lines such as C ii 158 µ m, O iii 88 µ m, C I 609 µ m, C i 370 µ m, and the rotational transitions of CO. Imaging such hidden cold CGM can lead to a breakthrough in galaxy evolution studies but requires a new facility with the specifications of the proposed Atacama Large Aperture Submillimeter Telescope (AtLAST). In this paper, we use theoretical and empirical arguments to motivate future ambitious CGM observations with AtLAST and describe the technical requirements needed for the telescope and its instrumentation to perform such science.
Ly$\alpha$ nebulae ubiquitously found around z>2 quasars can supply unique
constraints on the properties of the Circumgalactic Medium, such as its density
distribution, provided the quasar halo mass ...is known. We present a new method
to constrain quasar halo masses based on the line-of-sight velocity dispersion
maps of Ly$\alpha$ nebulae. By using MUSE-like mock observations obtained from
cosmological hydrodynamic simulations under the assumption of maximal quasar
fluorescence, we show that the velocity dispersion radial profiles of
Ly$\alpha$-emitting gas are strongly determined by gravity and that they are
thus self-similar with respect to halo mass when rescaled by the virial radius.
Through simple analytical arguments and by exploiting the kinematics of
HeII1640\.A emission for a set of observed nebulae, we show that Ly$\alpha$
radiative transfer effects plausibly do not change the shape of the velocity
dispersion profiles but only their normalisation without breaking their
self-similarity. Taking advantage of these results, we define the variable
$\eta^{140-200}_{40-100}$ as the ratio of the median velocity dispersion in two
specifically selected annuli and derive an analytical relation between
$\eta^{140-200}_{40-100}$ and the halo mass which can be directly applied to
observations. We apply our method to 37 observed quasar Ly$\alpha$ nebulae at
3<z<4.7 and find that their associated quasars are typically hosted by
~$10^{12.16 \pm 0.14}$ M$_{\odot}$ haloes independent of redshift within the
explored range. This measurement, which is completely independent of clustering
methods, is consistent with the lowest mass estimates based on quasar
auto-correlation clustering at z~3 and with quasar-galaxies cross-correlation
results.
Characterizing the physical conditions (density, temperature, ionization state, metallicity, etc) of the interstellar medium is critical to our understanding of the formation and evolution of ...galaxies. Here we present a multi-line study of the interstellar medium in the host galaxy of a quasar at z~6.4, i.e., when the universe was 840 Myr old. This galaxy is one of the most active and massive objects emerging from the dark ages, and therefore represents a benchmark for models of the early formation of massive galaxies. We used the Atacama Large Millimeter Array to target an ensemble of tracers of ionized, neutral, and molecular gas, namely the fine-structure lines: OIII 88\(\mu\)m, NII 122\(\mu\)m, CII 158\(\mu\)m, and CI 370\(\mu\)m and the rotational transitions of CO(7-6), CO(15-14), CO(16-15), and CO(19-18); OH 163.1\(\mu\)m and 163.4\(\mu\)m; and H\(_2\)O 3(0,3)-2(1,2), 3(3,1)-4(0,4), 3(3,1)-3(2,2), 4(0,4)-3(1,3), 4(3,2)-4(2,3). All the targeted fine-structure lines are detected, as are half of the targeted molecular transitions. By combining the associated line luminosities, the constraints on the dust temperature from the underlying continuum emission, and predictions from photoionization models of the interstellar medium, we find that the ionized phase accounts for about one third of the total gaseous mass budget, and is responsible for half of the total CII emission. It is characterized by high density (n~180 cm\(^{-3}\)), typical of HII regions. The spectral energy distribution of the photoionizing radiation is comparable to that emitted by B-type stars. Star formation also appears to drive the excitation of the molecular medium. We find marginal evidence for outflow-related shocks in the dense molecular phase, but not in other gas phases. This study showcases the power of multi-line investigations in unveiling the properties of the star-forming medium in galaxies at cosmic dawn.
We present observations using the NOrthern Extended Millimetre Array (NOEMA)
of CO and $\rm H_{2}O$ emission lines, and the underlying dust continuum in two
quasars at $z \sim 6$, i.e., P215-16 at ...$z$ = 5.78 and J1429+5447 at $z$ =
6.18. Notably, among all published CO SLEDs of quasars at $z \sim 6$, the two
systems reveal the highest and the lowest CO level of excitation, respectively.
Our radiative transfer modeling of the CO SLED of P215-16 suggests that the
molecular gas heated by AGN could be a plausible origin for the high CO
excitation. For J1429+5447, we obtain the first well-sampled CO SLED (from
transitions from 2-1 to 10-9) of a radio-loud quasar at $z\gtrsim 6$. Analysis
of the CO SLED suggests that a single photo-dissociation region (PDR) component
could explain the CO excitation in the radio-loud quasar J1429+5447. This work
highlights the utility of the CO SLED in uncovering the ISM properties in these
young quasar-starburst systems at the highest redshift. The diversity of the CO
SLEDs reveals the complexities in gas conditions and excitation mechanisms at
their early evolutionary stage.
We report new Northern Extended Millimeter Array (NOEMA) observations of the CII, NII and OI atomic fine structure lines and dust continuum emission of J1148+5251, a z=6.42 quasar, that probe the ...physical properties of its interstellar medium (ISM). The radially-averaged CII and dust continuum emission have similar extensions (up to \(\theta = 2.51^{+0.46}_{-0.25}\ \rm{arcsec}\), corresponding to \(r= 9.8^{+3.3}_{-2.1}\ \rm{kpc}\) accounting for beam-convolution), confirming that J1148+5251 is the quasar with the largest CII-emitting has reservoir known at these epochs.Moreover, if the CII emission is examined only along its NE-SW axis, a significant excess (\(>5.8\sigma\)) of CII emission (with respect to the dust) is detected. The new wide--bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad CII line wings that were reported in previous studies. We also report the first detection of the OI and (tentatively) NII emission lines in J1148+5251. Using Fine Structure Lines (FSL) ratios of the CII, NII, OI and previously measured CI emission lines, we show that J1148+5251 has similar ISM conditions compared to lower--redshift (ultra)-luminous infrared galaxies. CLOUDY modelling of the FSL ratios exclude X--ray dominated regions (XDR) and favours photodissociation regions (PDR) as the origin of the FSL emission. We find that a high radiation field (\(10^{3.5-4.5}\,G_0\)), high gas density (\(n \simeq 10^{3.5-4.5}\, \rm{cm}^{-3}\)) and HI column density of \(10^{23} \,\rm{cm^{-2}}\) reproduce the observed FSL ratios well.
A&A 685, A121 (2024) We present JWST/NIRSpec integral field data of the quasar PJ308-21 at
$z=6.2342$. As shown by previous ALMA and HST imaging, the quasar has two
companion sources, interacting ...with the quasar host galaxy. The high-resolution
G395H/290LP NIRSpec spectrum covers the $2.87-5.27\ \rm \mu m$ wavelength range
and shows the rest-frame optical emission of the quasar with exquisite quality
($S/N\sim 100-400$ per spectral element). Based on the H$\beta$ line from the
broad line region, we obtain an estimate of the black hole mass $M_{\rm
BH,H\beta}\sim 2.7\times 10^{9}\ \rm M_{\odot}$. This value is within a factor
$\lesssim 1.5$ of the H$\alpha$-based black hole mass from the same spectrum
($M_{\rm BH, H\alpha}\sim 1.93\times 10^{9}\ \rm M_{\odot}$) and is consistent
with a previous estimate relying on the MgII $\lambda 2799$ ($M_{\rm BH,
MgII}\sim 2.65\times 10^{9}\ \rm M_{\odot}$). All these $M_{\rm BH}$ are within
the $\sim 0.5$ dex intrinsic scatter of the adopted mass calibrations. The high
Eddington ratio of PJ308-21 $\lambda_{\rm Edd,H\beta}\sim 0.67$ ($\lambda_{\rm
Edd,H\alpha}\sim 0.96$) is in line with the overall quasar population at $z
\gtrsim 6$. The relative strengths of the OIII, FeII and H$\beta$ lines are
consistent with the empirical "Eigenvector 1" correlations as observed for low
redshift quasars. We find evidence for blueshifted OIII $\lambda 5007$
emission with a velocity offset $\Delta v_{\rm OIII}=-1922\pm 39$ km s$^{-1}$
from the systemic velocity and a $\rm FWHM(OIII)=2776^{+75}_{-74}$ km
s$^{-1}$. This may be the signature of an outflow from the nuclear region,
despite the true values of $\Delta v_{\rm OIII}$ and $\rm FWHM(OIII)$ are
likely more uncertain due to the blending with H$\beta$ and FeII lines. Our
study demonstrates the unique capabilities of NIRSpec in capturing quasar
spectra at cosmic dawn and studying their properties in unprecedented detail.
WISE J224607.6-052634.9 (W2246-0526) is a hot dust-obscured galaxy at \(z\) = 4.601, and the most luminous obscured quasar known to date. W2246-0526 harbors a heavily obscured supermassive black hole ...that is most likely accreting above the Eddington limit. We present observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in seven bands, including band 10, of the brightest far-infrared (FIR) fine-structure emission lines of this galaxy: OI\(_{63\mu m}\), OIII\(_{88\mu m}\), NII\(_{122\mu m}\), OI\(_{145\mu m}\), CII\(_{158\mu m}\), NII\(_{205\mu m}\), CI\(_{370\mu m}\), and CI\(_{609\mu m}\). A comparison of the data to a large grid of Cloudy radiative transfer models reveals that a high hydrogen density (\(n_{H}\sim3\times10^3\) cm\(^{-3}\)) and extinction (\(A_{V}\sim300\) mag), together with extreme ionization (\(log(U)=-0.5\)) and a high X-ray to UV ratio (\(\alpha_{ox}\geq-0.8\)) are required to reproduce the observed nuclear line ratios. The values of \(\alpha_{ox}\) and \(U\) are among the largest found in the literature and imply the existence of an X-ray-dominated region (XDR). In fact, this component explains the a priori very surprising non-detection of the OIII\(_{88\mu m}\) emission line, which is actually suppressed, instead of boosted, in XDR environments. Interestingly, the best-fitted model implies higher X-ray emission and lower CO content than what is detected observationally, suggesting the presence of a molecular gas component that should be further obscuring the X-ray emission over larger spatial scales than the central region that is being modeled. These results highlight the need for multiline infrared observations to characterize the multiphase gas in high redshift quasars and, in particular, W2246-0526 serves as an extreme benchmark for comparisons of interstellar medium conditions with other quasar populations at cosmic noon and beyond.
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