arXiv subjects

Marcel Neeleman

Publications and source records attributed to Marcel Neeleman.

At least 19 recordsLinked to original sources

arXiv2026

The Qz5 Survey (II): Metallicity Evolution of Damped Ly{\alpha} Systems Out to z$\sim$5

Damped Ly$\alpha$ absorbers (DLAs) are the highest \HI\ column density (\NHI) absorption line systems detected in the spectra of background quasars. DLAs dominate the neutral gas content of the Universe ($\Omega_{\rm HI}$) and are used to measure the metallicity evolution of \HI\ gas. In this work, we introduce a sample of five recently detected DLAs at $z > 4.7$, found in mid to high-resolution spectroscopy from VLT/X-shooter and Keck/HIRES. These DLAs were not pre-selected based on metallicity, enabling an unbiased study of the metallicity of HI gas at $z \sim 5$. We also search for DLAs unbiased in metallicity at $0<z<5.5$ from the literature, we apply a combined correction for dust depletion and $\alpha$-enhancement (assuming no depletion of S, Si, and Zn) to Fe abundances, and we measure the cosmic metallicity evolution of $\alpha$-elements using a linear fit with a slope of$-0.22 \pm 0.05$ dex per unit redshift. For the highest redshift bin, we find an \NHI weighted average of $\langle Z \rangle = -2.00$. This value is $4.4\sigma$ deviant from the trend recovered at $z < 4.7$ and a K-S test comparison gives a $2.4 \sigma$ difference. We conclude that the metallicity of HI gas sharply decreases at $z \sim 5$, in agreement with previous tentative evidence. This sharp decrease may be connected with the onset of the enrichment of galaxies' circumgalactic media or with the end of cosmic reionization, though we cannot exclude that it is driven by small sample statistics.

astro-ph.GA↗

arXiv2025

ALMA and JWST Imaging of $z\ >\ 6$ Quasars: No Spatial Position Offset Observed Between Quasars and Their Host Galaxies

We present a study determining the spatial offset between the position of the supermassive black hole (as traced through their broad line regions) and the host galaxy in six $z > 6$ quasars. We determined the host galaxy's position from $\lesssim$$0.1^{\prime\prime}$ ($\lesssim$ 600 pc) resolution Atacama Large Millimeter/sub-millimeter Array (ALMA) [CII] 158 $\mu m$ and corresponding dust continuum imaging. We determined the quasar's position from $\lesssim$ 400 pc resolution James Webb Space Telescope Near-Infrared Camera (JWST NIRCam) imaging. We estimated the observational uncertainties on the quasar's position using astrometric data from the Global Astrometric Interferometer for Astrophysics (GAIA) of field stars within the NIRCam images. We find that all six quasars are found within the central $\sim 400$ pc of their host galaxy dust continuum and [CII] emission. Apparent offsets seen in rest-frame optical JWST observations are not detected in our ALMA data, suggesting they likely result from dust obscuration rather than a true physical separation between the SMBH and its host galaxy. Kinematic modeling of these data further reveals that none of the galaxies show evidence for recent merger activity, and most of the galaxies can be accurately modeled using a simple disk model. The lack of an offset supports theoretical models that predict that positional offset within these galaxies are either short-lived or intrinsically rare.

astro-ph.GA↗

arXiv2025

A [CII]-158-micron Survey of DLA galaxies at z~4: Observations of Dense and Metal-Enriched Neutral Gas within the Circumgalactic Medium of Star-Forming Galaxies

We present a survey undertaken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the galaxies associated with a representative sample of 16 damped Ly-alpha absorbers (DLAs) at z~4.1-4.5, using the [CII]-158-micron ([CII]) line. We detect seven [CII]-emitting galaxies in the fields of 5 DLAs, all of which have absorption metallicity [M/H] > -1.5. We find that the detectability of these HI-selected galaxies with ALMA is a strong function of DLA metallicity, with a detection rate of 71^{+11}_{-20}% for DLAs with [M/H] > -1.5 and 0^{+18}% for DLAs with [M/H] <-1.5. The identified DLA galaxies have far-infrared properties similar to those of typical star-forming galaxies at z ~ 4, with estimated obscured star-formation rates ranging from ~6 Msun/yr to 110 Msun/yr. High-metallicity DLAs therefore provide an efficient way to identify and study samples of high-redshift, star-forming galaxies without preselecting the galaxies by their emission properties. The agreement between the velocities of the metal absorption lines of the DLA and the [CII] emission line of the DLA galaxy indicates that the metals within the DLA originated in the galaxy. With observed impact parameters between 14 and 59 kpc, this indicates that star-forming galaxies at z ~ 4 have a substantial reservoir of dense, cold neutral gas within their circumgalactic medium that has been enriched with metals from the galaxy.

astro-ph.GA↗

arXiv2025

Kiloparsec-Scale Alignment of a Radio Jet with Cool Gas and Dust in a z~6 Quasar

We present high-angular resolution (0.068", ~400pc) ALMA imaging of the [CII] line and dust continuum emission of PSO J352.4034-15.3373, a radio-loud quasar at z=5.83. The observations reveal a remarkably close match between the orientation of the [CII] and thermal dust emission mapped by ALMA, and radio synchrotron emission of a radio jet previously mapped by the VLBA. This narrow alignment extends over ~4kpc, reminiscent of the well-studied 'alignment effect' in lower-redshift radio galaxies. The [CII] kinematics show a linear increase in velocity with galactocentric radii up to ~200 km/s at r=2kpc, consistent with bulk motions within the galaxy potential, and not relativistic jet motions. The kinematics and respective morphologies are consistent with a picture in which the relativistic jet injects energy into the interstellar medium (potentially leading to subsequent star formation), giving rise to the observed alignment and significant (> 100 km/s) [CII] velocity dispersion within the host galaxy on kiloparsec scales. Indeed, the astonishingly close alignment and narrow linearity of the radio jet with the [CII] and dust emission are hard to conceive without some fundamental relationship between the two.

astro-ph.GA↗

arXiv2025

A massive HI-absorption-selected galaxy at $z\approx2.356$

We use the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) to detect $\rm CO(1-0)$, $\rm CO(3-2)$, and rest-frame 349-GHz continuum emission from an HI-selected galaxy, DLA1020+2733g, at $z\approx2.3568$ in the field of the $z=2.3553$ damped Lyman-$\alpha$ absorber (DLA) towards QSO J1020+2733. The VLA $\rm CO(1-0)$ detection yields a molecular gas mass of $(2.84\pm0.42)\times10^{11}\times(\alpha_{\rm CO}/4.36)\,\rm{M_\odot}$, the largest ever measured in an HI-selected galaxy. The DLA metallicity is $+0.28 \pm 0.16$, from the ZnII$\, \lambda2026$\r{A} absorption line detected in a Keck Echellette Spectrograph and Imager spectrum. This continues the trend of high-metallicity DLAs being frequently associated with massive galaxies. We obtain a star-formation rate (SFR) of $\lesssim400~$M$_\odot~$yr$^{-1}$ from the rest-frame 349-GHz continuum emission, and a relatively long molecular gas depletion timescale of $\gtrsim0.6~$Gyr. The excitation of the J=3 rotational level is sub-thermal, with $r_{31}\equiv{L'_{\rm{CO(3-2)}}/L'_{\rm{CO(1-0)}}}=0.513\pm0.081$, suggesting that DLA1020+2733g has a low SFR surface density. The large velocity spread of the CO lines, $\approx500~\rm km~s^{-1}$, and the long molecular gas depletion timescale suggest that DLA1020+2733g is likely to be a cold rotating-disk galaxy.

astro-ph.GA↗

arXiv2025

ALMA 360 pc high-frequency observations reveal warm dust in the center of a $z=6.9$ quasar

The temperature of the cold dust in z>6 galaxies is a potential tracer of Active Galactic Nucleus (AGN) and stellar feedback, and is the dominant source of uncertainty in inferring properties from the far-infrared (FIR) emission of these galaxies. We present the first resolved dust temperature map in a $z>6$ quasar host galaxy. We combine new 360 pc resolution ALMA Band 9 continuum observations with literature 190 pc Band 6 observations to derive the dust temperature and opacity at 0.1<r<0.5 kpc scales in a $z=6.9$ luminous quasar host galaxy (J2348-3054). We find that the dust temperature (and opacity) increases at the center (r<216 pc) of the galaxy up to $T_d=73-88$ K, and potentially up to $T_d<149$ K at r<110 pc. The combination of the resolved and integrated FIR Spectral Energy Distribution (SED) further reveal a dust temperature gradient and a significant contribution of the AGN hot dust torus at $\nu_{\rm{obs}}\gtrsim 700$ GHz. By taking into account the torus contribution and resolved optically-thick emission, we derive a total infrared luminosity ($L_{TIR}=8.78\pm0.10)\times 10^{12}L_\odot$) and corresponding star-formation rate (SFR$=1307\pm15\ M_\odot\ \rm{yr}^{-1}$), that are at least a factor $\sim 3.6$ ($\sim0.56$ dex) lower than previous measurements assuming optically-thin emission. We compare the resolved dust temperature, mass and IR luminosity profiles to simulations where they are only reproduced by models in which the AGN radiation heats the dust in the center of the galaxy. Our observations provide evidence that dust in J2348--3054 cannot be assumed to be uniformly cold and optically thin. Whether J2348-3054 is representative of the larger population of high-redshift quasars and galaxies remains to be determined with dedicated high-resolution and high-frequency ALMA observations.

astro-ph.GA↗

arXiv2025

The Qz5 Survey (I): How the HI Mass Density of the Universe Evolves With Cosmic Time

We report that the neutral hydrogen (HI) mass density of the Universe ($\rho_{HI}$) increases with cosmic time since $z \sim 5$, peaks at $z \sim 3$, and then decreases toward $z \sim 0$. This is the first result of Qz5, our spectroscopic survey of 63 quasars at $z \gtrsim 5$ with VLT/X-SHOOTER and Keck/ESI aimed at characterizing intervening HI gas absorbers at $z \sim 5$. The main feature of Qz5 is the high resolution ($R \sim 7000 - 9000$) of the spectra, which allows us to (1) accurately detect high column density HI gas absorbers in an increasingly neutral intergalactic medium at $z \sim 5$ and (2) determine the reliability of previous $\rho_{HI}$ measurements derived with lower resolution spectroscopy. We find 5 intervening Damped Ly$\alpha$ absorbers (DLAs) at $z > 4.5$, which corresponds to the lowest DLA incidence rate ($0.034^{0.05}_{0.02}$) at $z \gtrsim 2$. We also measure the lowest $\rho_{HI}$ at $z \gtrsim 2$ from our sample of DLAs and subDLAs, corresponding to $\rho_{HI} = 0.56^{0.82}_{0.31} \times 10^8~$M$_{\odot}~$Mpc$^{-3}$ at $z \sim 5$. Taking into account our measurements at $z \sim 5$ and systematic biases in the DLA detection rate at lower spectral resolutions, we conclude that $\rho_{HI}$ doubles from $z \sim 5$ to $z \sim 3$. From these results emerges a qualitative agreement between how the cosmic densities of HI gas mass, molecular gas mass, and star-formation rate build up with cosmic time.

astro-ph.GA↗

arXiv2024

Pushing ALMA to the limit: 140 pc resolution observations of a z=6.6 quasar-galaxy merger resolve strikingly different morphologies of dust continuum and [CII] 158 um emission

We present $0."026$ $(140\ \rm{pc})$ resolution ALMA observations of [C II] $158\ \mu\rm{m}$ and dust continuum emission of the $z=6.6$ quasar J0305--3150, resolved over $\sim 300-400$ independent resolution elements. The dust continuum emission is compact with $\sim 80\%$ recovered within $r<0."3$ $(1.6\ \rm{kpc})$, whereas the [C II] emission profile is composed of a central Gaussian ($r<0."4$, i.e. $<2.2\ \rm{kpc}$) and an extended component (detected up to $\sim 10\ \rm{kpc}$ at $>3\sigma$). We infer a direct contribution of the quasar to the observed 260\ \rm{GHz} continuum $S_{\nu,\rm{QSO}} / S_{\nu,\rm{QSO+Host}} \lesssim 1\%$. We report the detection of FIR-detected star-forming clumps with $r<200 \ \rm{pc}$ and properties similar to that of rest-frame UV-optical clumps reported in the literature. The $200\ \rm{pc}$ resolved [C II]/FIR ratio follows the global relation with the FIR surface brightness established in low- and high-redshift galaxies, even at the quasar location. We find that dust continuum is emitted in regions of $\sim0."02-0."04$ consistent with the size of photo-dissociation regions (PDR), whereas $50\%$ of the [C II] originates from larger physical scales ($\theta \gtrsim 2"$). The large-scale [C II] emission presents a velocity gradient aligned with a nearby companion with perturbed kinematics, and misaligned with the kinematics of the small-scale emission. The absence of significant [C II] emission by structures with physical scale $\lesssim 1\ \rm{kpc}$ implies that [C II] emission is not produced in dense PDR located at the boundary of Giant Molecular Clouds. We argue instead that [C II] is produced in low-density PDRs in the interstellar medium and diffuse HI gas tidally-stripped during the ongoing merger.

astro-ph.GA↗

arXiv2024

A quasar-galaxy merger at $z\sim 6.2$: rapid host growth via accretion of two massive satellite galaxies

We present JWST/NIRSpec Integral Field Spectroscopy in the rest-frame optical bands of the system PJ308-21, a quasar at $z=6.2342$ caught as its host galaxy interacts with companion galaxies. We detect spatially extended emission of several emission lines (H$\alpha$, H$\beta$, [OIII], [NII], [SII], HeII), which we use to study the properties of the ionized phase of the interstellar medium: the source and hardness of the photoionizing radiation field, metallicity, dust reddening, electron density and temperature, and star formation. We also marginally detect continuum starlight emission associated with the companion sources. We find that at least two independent satellite galaxies are part of the system. While the quasar host appears highly enriched and obscured, with AGN-like photoionization conditions, the western companion shows minimal dust extinction, low metallicity ($Z\sim0.4$ Z$_\odot$), and star-formation driven photoionization. The eastern companion shows higher extinction and metallicity ($Z\sim0.8$ Z$_\odot$) compared to the western companion, and it is at least partially photoionized by the nearby quasar. We do not find any indication of AGN in the companion sources. Our study shows that while the quasar host galaxy is already very massive ($M_{\rm dyn}>10^{11}$ M$_\odot$), it is still rapidly building up by accreting two relatively massive ($M_{\rm star}\sim 10^{10}$ M$_\odot$) companion sources. This dataset showcases the power of JWST in exposing the build-up of massive galaxies in the first Gyr of the Universe.

astro-ph.GA↗

arXiv2024

A quasar-galaxy merger at $z\sim6.2$: black hole mass and quasar properties from the NIRSpec spectrum

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.

astro-ph.GA↗

arXiv2024

The cold molecular gas in z$\gtrsim$6 quasar host galaxies

Probing the molecular gas reservoirs of z>~6 quasar (QSO) host galaxies is fundamental to understanding the coevolution of star formation and black hole growth in these extreme systems. Yet, there is still an inhomogeneous coverage of molecular gas tracers. To measure the average excitation and mass of the molecular gas reservoirs in the brightest z>6.5 QSO hosts, we combined new observations of CO(2-1) emission with existing observations of CO(6-5), CO(7-6), [C I], [C II], and dust-continuum emission. We reduced and analysed the VLA observations of CO(2-1) in three z=6.5-6.9 QSO hosts -- the highest redshift observations of CO(2-1) to date. By combining these with the nine z=5.7-6.4 QSO hosts for which CO(2-1) has already been observed, we studied the spread in molecular gas masses and CO excitation. Two of our three QSOs, were undetected in CO(2-1), implying more highly excited CO than in the z=6.4 QSO J1148+5251. We detected CO(2-1) at $5.1\sigma$ for our highest-redshift target, J2348-3054, yielding a molecular gas mass of $(1.2\pm0.2)\times 10^{10}\, \mathrm{M}_\odot$. This molecular gas mass is equivalent to the lower limit on the dynamical mass measured from resolved [C II] observations, implying little mass in stars or neutral gas within the [C II]-emitting region. On average, these QSO hosts have far higher CO(6-5)-, CO(7-6)-, and [C II] vs CO(2-1) line ratios than local AGN hosts; with a mean CO(6-5)-to-CO(1-0) line luminosity ratio of $r_{6,1}=0.9\pm0.2$. Our new CO(2-1) observations show that even at 780 Myr after the Big Bang, QSO host galaxies can already have molecular gas masses of $10^{10}$ M$_\odot$, consistent with a picture in which these z>6 QSOs reside in massive starbursts that are coevolving with the supermassive black holes. Our results imply the presence of extremely dense and warm molecular gas reservoirs illuminated by strong interstellar radiation fields.

astro-ph.GA↗

arXiv2023

A survey of Ly$\alpha$ emission around Damped Ly$\alpha$ absorbers at $z \approx 2$ with the Keck Cosmic Web Imager

We present Keck Cosmic Web Imager (KCWI) Ly$\alpha$ integral field spectroscopy of the fields surrounding 14 Damped Ly$\alpha$ absorbers (DLAs) at $z \approx 2$. Of these 14 DLAs, 9 have high metallicities ([M/H]$~> -0.3$), and 4 of those 9 feature a CO-emitting galaxy at an impact parameter $\lesssim 30$ kpc. Our search reaches median Ly$\alpha$ line flux sensitivities of $\sim 2 \times 10^{-17}$ erg s$^{-1}$ cm$^{-2}$ over apertures of $\sim6$ kpc and out to impact parameters of $\sim50$ kpc. We recover the Ly$\alpha$ flux of three known Ly$\alpha$-emitting H I-selected galaxies in our sample. In addition, we find two Ly$\alpha$ emitters at impact parameters of $\approx 50-70$ kpc from the high metallicity DLA at $z \approx 1.96$ toward QSO B0551-366. This field also contains a massive CO-emitting galaxy at an impact parameter of $\approx 15$ kpc. Apart from the field with QSO B0551-366, we do not detect significant Ly$\alpha$ emission in any of the remaining 8 high-metallicity DLA fields. Considering the depth of our observations and our ability to recover previously known Ly$\alpha$ emitters, we conclude that H I-selected galaxies associated with high-metallicity DLAs at $z \approx 2$ are dusty, and therefore might feature low Ly$\alpha$ escape fractions. Our results indicate that complementary approaches -- using Ly$\alpha$, CO, H$\alpha$, and [C II] 158$\mu$m emission -- are necessary to identify the wide range of galaxy types associated with $z \approx 2$ DLAs.

astro-ph.GA↗

arXiv2023

ALMA 400pc Imaging of a z=6.5 Massive Warped Disk Galaxy

We present 0.075 (~400 pc) resolution ALMA observations of the [CII] and dust continuum emission from the host galaxy of the z=6.5406 quasar, P036+03. We find that the emission arises from a thin, rotating disk with an effective radius of 0.21" (1.1 kpc). The velocity dispersion of the disk is consistent with a constant value of 66.4+-1.0 km/s, yielding a scale height of 80+-30 pc. The [CII] velocity field reveals a distortion that we attribute to a warp in the disk. Modeling this warped disk yields an inclination estimate of 40.4+-1.3 degrees and a rotational velocity of 116+-3 km/s. The resulting dynamical mass estimate of (1.96+-0.10) x 10^10 Msun is lower than previous estimates, which strengthens the conclusion that the host galaxy is less massive than expected based on local scaling relations between the black hole mass and the host galaxy mass. Using archival MUSE Ly-alpha observations, we argue that counter-rotating halo gas could provide the torque needed to warp the disk. We further detect a region with excess (15-sigma) dust continuum emission, which is located 1.3 kpc northwest of the galaxy's center and is gravitationally unstable (Toomre-Q < 0.04). We posit this is a star-forming region whose formation was triggered by the warp, because the region is located within a part of the warped disk where gas can efficiently lose angular momentum. The combined ALMA and MUSE imaging provides a unique view of how gas interactions within the disk-halo interface can influence the growth of massive galaxies within the first billion years of the universe.

astro-ph.GA↗

arXiv2023

Searching for [CII] Emission from the First Sample of $z\sim 6$ OI Absorption-Associated Galaxies with ALMA

We report the first statistical analyses of [CII] and dust continuum observations in six strong OI absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/Submillimeter Array (ALMA). Combined with one [CII] emitter reported in Wu et al. (2021), we detect one OI-associated [CII] emitter in six fields. At redshifts of OI-absorbers in non-detection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between $\pm200\ {\rm km\ s^{-1}}$. The averaged [CII]-detection upper limit is $< 0.06$ Jy ${\rm km\ s^{-1}}$ (3$\sigma$), corresponding to the [CII] luminosity of $L_{\rm [CII]} <5.8\times 10^7\ L_{\odot}$ and the [CII]-based star formation rate of ${\rm SFR_{\rm [CII]}} < 5.5$ $M_\odot$ yr$^{-1}$. Cosmological simulations suggest that only $\sim10^{-2.5}$ [CII] emitters around [OI] absorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with S/N of $\approx4.3$ at large impact parameters ($>50$ kpc) and having larger outflow velocities within $\pm 600$ km s$^{-1}$. If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side.

astro-ph.GA↗

arXiv2023

ALMA 300 pc resolution imaging of a z=6.79 quasar: no evidence for supermassive black hole influence on the [C II] kinematics

We present Atacama Large Millimeter/submillimeter Array (ALMA) [C II] 158 $\mu \rm{m}$ and dust continuum observations of the $z=6.79$ quasar J0109--3047 at a resolution of $0."045$ ($\sim$300 pc). The dust and [C II] emission are enclosed within a $\sim 500\, \rm{pc}$ radius, with the central beam ($r<144\ \rm{pc}$) accounting for $\sim$25\% (8\%) of the total continuum ([C II]) emission. The far--infrared luminosity density increases radially from $\sim$5 $\times 10^{11} L_\odot\ \rm{kpc}^{-2}$ to a central value of $\sim$70 $\times 10^{11} L_\odot\ \rm{kpc}^{-2}$ (SFRD $\sim$50-700 $M_\odot\ \rm{yr}^{-1}\ \rm{kpc}^{-2}$). The [C II] kinematics are dispersion-dominated with a constant velocity dispersion of $137 \pm 6 \,\rm{km\ s}^{-1}$. The constant dispersion implies that the underlying mass distribution is not centrally peaked, consistent with the expectations of a flat gas mass profile. The lack of an upturn in velocity dispersion within the central beam is inconsistent with a black hole mass greater than $M_{\rm{BH}}<6.5\times 10^{8}\ M_\odot\ (2\sigma$ level), unless highly fine-tuned changes in the ISM properties conspire to produce a decrease of the gas mass in the central beam comparable to the black hole mass. Our observations therefore imply either that a) the black hole is less massive than previously measured or b) the central peak of the far-infrared and [C II] emission are not tracing the location of the black hole, as suggested by the tentative offset between the near-infrared position of the quasar and the ALMA continuum emission.

astro-ph.GA↗

arXiv2022

Jansky Very Large Array detections of CO(1-0) emission in HI-absorption-selected galaxies at $z \gtrsim 2$

We report a Karl G. Jansky Very Large Array search for redshifted CO(1-0) emission from three HI-absorption-selected galaxies at $z \approx 2$, identified earlier in their CO(3-2) or CO(4-3) emission. We detect CO(1-0) emission from DLA B1228-113 at $z\approx2.1933$ and DLA J0918+1636 at $z\approx2.5848$; these are the first detections of CO(1-0) emission in high-$z$ HI-selected galaxies. We obtain high molecular gas masses, $\rm M_{mol}\approx10^{11}\times(\alpha_{\rm CO}/4.36)\ M_\odot$, for the two objects with CO(1-0) detections, which are a factor of $\approx1.5-2$ lower than earlier estimates. We determine the excitation of the mid$-J$ CO rotational levels relative to the $J=1$ level, r$_{ J1}$, in HI-selected galaxies for the first time, obtaining r$_{\rm 31}=1.00\pm0.20$ and r$_{\rm 41}=1.03\pm0.23$ for DLA J0918+1636, and r$_{\rm 31}=0.86\pm0.21$ for DLA B1228-113. These values are consistent with thermal excitation of the $J=3,4$ levels. The excitation of the $J=3$ level in the HI-selected galaxies is similar to that seen in massive main-sequence and sub-mm galaxies at $z\gtrsim2$, but higher than that in main-sequence galaxies at $z\approx1.5$; the higher excitation of the galaxies at $z\gtrsim2$ is likely to be due to their higher star-formation rate (SFR) surface density. We use Hubble Space Telescope Wide Field Camera 3 imaging to detect the rest-frame near-ultraviolet emission of DLA B1228-113, obtaining an NUV SFR of $4.44\pm0.47$ M$_{\odot}$ yr$^{-1}$, significantly lower than that obtained from the total infrared luminosity, indicating significant dust extinction in the $z\approx2.1933$ galaxy.

astro-ph.GA↗

arXiv2022

A Massive, Dusty HI-Absorption-Selected Galaxy at $z \approx 2.46$ Identified in a CO Emission Survey

We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array (ALMA) search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] $\geq -1.03$) damped Lyman-$\alpha$ absorbers (DLAs) at $z\approx1.64-2.51$. Our observations yielded one new detection of CO(3-2) emission from a galaxy at $z=2.4604$ using NOEMA, associated with the $z=2.4628$ DLA towards QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of $\approx56^{+38}_{-24}$ % and $\approx11^{+26}_{-9}$ %, respectively, in the fields of DLAs with ${\rm [M/H]}>-0.3$ and ${\rm [M/H]}<-0.3$. Further, the HI-selected galaxies associated with five DLAs with [M/H] $>-0.3$ all have high molecular gas masses, $\gtrsim5\times10^{10}\ {\rm M}_\odot$. This indicates that the highest-metallicity DLAs at $z\approx2$ are associated with the most massive galaxies. The newly-identified $z\approx2.4604$ HI-selected galaxy, DLA0201+365g, has an impact parameter of $\approx7$ kpc to the QSO sightline, and an implied molecular gas mass of $(5.04\pm0.78) \times10^{10}\times(\alpha_{\rm CO}/4.36)\times(r_{31}/0.55)\ {\rm M}_\odot$. Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield non-detections of rest-frame NUV and FUV emission, and a $5\sigma$ upper limit of 2.3 M$_\odot$ yr$^{-1}$ on the unobscured star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around two orders of magnitude larger than that of star-forming galaxies at similar redshifts.

astro-ph.GA↗

arXiv2022

The Decoupled Kinematics of high-z QSO Host Galaxies and their Lya halos

We present a comparison of the interstellar medium traced by [CII] (ALMA), and ionised halo gas traced by Lya (MUSE), in and around QSO host galaxies at z~6. To date, 18 QSOs at this redshift have been studied with both MUSE and high-resolution ALMA imaging; of these, 8 objects display a Lya halo. Using datacubes matched in velocity resolution, we compare and contrast the spatial and kinematic information of the Lya halos and the host galaxies' [CII] (and dust-continuum) emission. We find that the Lya halos extend typically 3-30 times beyond the interstellar medium of the host galaxies. The majority of the Lya halos do not show ordered motion in their velocity fields, whereas most of the [CII] velocity fields do. In those cases where a velocity gradient can be measured in Lya, the kinematics do not align with those derived from the [CII] emission. This implies that the Lya emission is not tracing the outskirts of a large rotating disk that is a simple extension of the central galaxy seen in [CII] emission. It rather suggests that the kinematics of the halo gas are decoupled from those of the central galaxy. Given the scattering nature of Lya, these results need to be confirmed with JWST IFU observations that can constrain the halo kinematics further using the non-resonant Ha line.

astro-ph.GA↗