分类： 天文学 >> 天文学 提交时间： 2023-02-21
Yali Shao
Ran Wang
Axel Weiss
Jeff Wagg
Chris L. Carilli
Michael A. Strauss
Fabian Walter
Pierre Cox
Xiaohui Fan
Karl M. Menten
Desika Narayanan
Dominik Riechers
Frank Bertoldi
Alain Omont
Linhua Jiang
摘要： We present Atacama Large Millimeter/submillimeter Array (ALMA) sub-kiloparsec- to kiloparsec-scale resolution observations of the [C ii], CO (98), and OH+ (1101) lines along with their dust continuum emission toward the far-infrared (FIR) luminous quasar SDSS J231038.88+185519.7 at z = 6.0031, to study the interstellar medium distribution, the gas kinematics, and the quasar-host system dynamics. We decompose the intensity maps of the [C ii] and CO (98) lines and the dust continuum with two-dimensional elliptical Srsic models. The [C ii] brightness follows a flat distribution with a Srsic index of 0.59. The CO (98) line and the dust continuum can be fit with an unresolved nuclear component and an extended Srsic component with a Srsic index of 1, which may correspond to the emission from an active galactic nucleus dusty molecular torus and a quasar host galaxy, respectively. The different [C ii] spatial distribution may be due to the effect of the high dust opacity, which increases the FIR background radiation on the [C ii] line, especially in the galaxy center, significantly suppressing the [C ii] emission profile. The dust temperature drops with distance from the center. The effective radius of the dust continuum is smaller than that of the line emission and the dust mass surface density, but is consistent with that of the star formation rate surface density. This may indicate that the dust emission is a less robust tracer of the dust and gas distribution but is a decent tracer of the obscured star formation activity. The OH+ (1101) line shows a P-Cygni profile with an absorption at 400 km/s, which may indicate an outflow with a neutral gas mass of (6.2 1.2) 108 M along the line of sight. We employed a three-dimensional tilted ring model to fit the [C ii] and CO (98) data cubes. The two lines are both rotation dominated and trace identical disk geometries and gas motions. This suggest that the [C ii] and CO (98) gas are coplanar and corotating in this quasar host galaxy. The consistent circular velocities measured with [C ii] and CO (98) lines indicate that these two lines trace a similar gravitational potential. We decompose the circular rotation curve measured from the kinematic model fit to the [C ii] line into four matter components (black hole, stars, gas, and dark matter). The quasar-starburst system is dominated by baryonic matter inside the central few kiloparsecs. We constrain the black hole mass to be 2.97+0.51 0.77 109 M ; this is the first time that the dynamical mass of a black hole has been measured at z 6. This mass is consistent with that determined using the scaling relations from quasar emission lines. A massive stellar component (on the order of 109 M ) may have already existed when the Universe was only 0.93 Gyr old. The relations between the black hole mass and the baryonic mass of this quasar indicate that the central supermassive black hole may have formed before its host galaxy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yunjing Wu
Zheng Cai
Fengwu Sun
Fuyan Bian
Xiaojing Lin
Zihao Li
Mingyu Li
Franz E. Bauer
Eiichi Egami
Xiaohui Fan
Jorge González-López
Jianan Li
Feige Wang
Jinyi Yang
Shiwu Zhang
Siwei Zou
摘要： Spiral arms serve crucial purposes in star formation and galaxy evolution. In this paper, we report the identification of A2744-DSG-$z3$, a dusty, multiarm spiral galaxy at $z=3.059$ using the James Webb Space Telescope (JWST) NIRISS imaging and grism spectroscopy. A2744-DSG-$z3$ was discovered as a gravitationally lensed sub-millimeter galaxy with ALMA. This is the most distant stellar spiral structure seen thus far, consistent with cosmological simulations which suggest $z\approx3$ as the epoch when spirals emerge. Thanks to the gravitational lensing and excellent spatial resolution of JWST, the spiral arms are resolved with a spatial resolution of $\approx290$\,pc. Based on SED fitting, the spiral galaxy has a de-lensed star formation rate of $85\pm30 \ M_{\odot}$ yr$^{-1}$, and a stellar mass of $\approx10^{10.6}M_{\odot}$, indicating that A2744-DSG-$z3$ is a main-sequence galaxy. After fitting the spiral arms, we find a stellar effective radius ($R_{e, \rm{star}}$) of $5.0\pm1.5$ kpc. Combing with ALMA measurements, we find that the effective radii ratio between dust and stars is $\approx0.4$, similar to {those} of massive SFGs at $z\sim2$, indicating a compact dusty core in A2744-DSG-$z3$. Moreover, this galaxy appears to be living in a group environment: including A2744-DSG-$z3$, at least three galaxies at $z=3.05 - 3.06$ {are} spectroscopically confirmed by JWST/NIRISS and ALMA, residing within a lensing-corrected projected scale of $\approx 70$ kpc. This, along with the asymmetric brightness profile, further suggests that the spiral arms may be triggered by minor merger events at $z\gtrsim3$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jinyi Yang
Xiaohui Fan
Ansh Gupta
Adam Myers
Nathalie Palanque-Delabrouille
Feige Wang
Christophe Yèche
Jessica Nicole Aguilar
Steven Ahlen
David Alexander
David Brooks
Kyle Dawson
Axel de la Macorra
Arjun Dey
Govinda Dhungana
Kevin Fanning
Andreu Font-Ribera
Satya Gontcho
Julien Guy
Klaus Honscheid
摘要： We report the first results of a high-redshift ($z$ >~ 5) quasar survey using the Dark Energy Spectroscopic Instrument (DESI). As a DESI secondary target program, this survey is designed to carry out a systematic search and investigation of quasars at $z$ >~ 5, up to redshift 6.8. The target selection is based on the DESI Legacy Imaging Surveys (the Legacy Surveys) DR9 photometry, combined with the Pan-STARRS1 data and $J$-band photometry from public surveys. A first quasar sample has been constructed from the DESI Survey Validation 3 (SV3) and first-year observations until May 2022. This sample includes more than 400 new quasars at redshift 4.7 = 5, more than one third of existing quasars previously published at this redshift. The observations so far result in an average success rate of 23% at $z$ > 4.7. The current spectral dataset has already allowed analysis of interesting individual objects (e.g., quasars with damped Ly$\alpha$ absorbers and broad absorption line features), and statistical analysis will follow the survey's completion. A set of science projects will be carried out leveraging this program, including quasar luminosity function, quasar clustering, intergalactic medium, quasar spectral properties, intervening absorbers, and properties of early supermassive black holes. Additionally, a sample of 38 new quasars at $z$ ~ 3.8-5.7 discovered from a pilot survey in the DESI SV1 is also published in this paper.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Da-Ming Yang
Jan-Torge Schindler
Riccardo Nanni
Joseph F. Hennawi
Eduardo Bañados
Xiaohui Fan
Anniek Gloudemans
Huub Rottgering
Feige Wang
Jinyi Yang
摘要： We present the high-$z$ quasar candidate archive (HzQCA), summarizing the spectroscopic observations of 174 $z\gtrsim5$ quasar candidates using Keck/LRIS, Keck/MOSFIRE, and Keck/NIRES. We identify 7 candidates as $z\sim 6$ quasars 3 of them newly reported here, and 51 candidates as brown dwarfs. In the remaining sources, 74 candidates are unlikely to be quasars; 2 sources are inconclusive; the others could not be fully reduced or extracted. Based on the classifications we investigate the distributions of quasars and contaminants in color space with photometry measurements from DELS ($z$), VIKING/UKIDSS ($YJHK_s$/$YJHK$), and un\textit{WISE} ($W1W2$). We find that the identified brown dwarfs are not fully consistent with the empirical brown dwarf model that is commonly used in quasar candidate selection methods. To refine spectroscopic confirmation strategies, we simulate synthetic spectroscopy of high-$z$ quasars and contaminants for all three instruments. The simulations utilize the spectroscopic data in HzQCA. We predict the required exposure times for quasar confirmation and propose and optimal strategy for spectroscopic follow-up observations. For example, we demonstrate that we can identify a $m_J=21.5$ at $z=7.6$ or a $m_J=23.0$ at $z=7.0$ within 15\,min of exposure time with LRIS. With the publication of the HzQCA we aim to provide guidance for future quasar surveys and candidate classification.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Haibin Zhang
Zheng Cai
Mingyu Li
Yongming Liang
Nobunari Kashikawa
Ke Ma
Yunjing Wu
Qiong Li
Sean D. Johnson
Satoshi Kikuta
Masami Ouchi
Xiaohui Fan
摘要： We report the large scale structure and clustering analysis of Ly$\alpha$ emitters (LAEs) and Ly$\alpha$ blobs (LABs) at $z=2.2-2.3$. Using 3,341 LAEs, 117 LABs, and 58 bright (Ly$\alpha$ luminosity $L_{\rm Ly\alpha}>10^{43.4}$ erg s$^{-1}$) LABs at $z=2.2-2.3$ selected with Subaru/Hyper Suprime-Cam (HSC), we calculate the LAE overdensity to investigate the large scale structure at $z=2$. We show that 74% LABs and 78% bright LABs locate in overdense regions, which is consistent with the trend found by previous studies that LABs generally locate in overdense regions. We find that one of our 8 fields dubbed J1349 contains $39/117\approx33\%$ of our LABs and $22/58\approx38\%$ of our bright LABs. A unique and overdense $24'\times12'$ ($\approx 40\times20$ comoving Mpc$^2$) region in J1349 has 12 LABs (8 bright LABs). By comparing to SSA22 that is one of the most overdense LAB regions found by previous studies, we show that the J1349 overdense region contains $\geq 2$ times more bright LABs than the SSA22 overdense region. We calculate the angular correlation functions (ACFs) of LAEs and LABs in the unique J1349 field and fit the ACFs with a power-law function to measure the slopes. The slopes of LAEs and LABs are similar, while the bright LABs show a $\approx 2$ times larger slope suggesting that bright LABs are more clustered than faint LABs and LAEs. We show that the amplitudes of ACFs of LABs are higher than LAEs, which suggests that LABs have a $\approx 10$ times larger galaxy bias and field-to-field variance than LAEs. The strong field-to-field variance is consistent with the large differences of LAB numbers in our 8 fields.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Haibin Zhang
Zheng Cai
Yongming Liang
Ke Ma
Nobunari Kashikawa
Mingyu Li
Yunjing Wu
Qiong Li
Sean D. Johnson
Masami Ouchi
Xiaohui Fan
摘要： In this paper, we present a Ly$\alpha$ halo extended to $\sim200$ kpc identified by stacking $\sim 3300$ Ly$\alpha$ emitters at $z=2.2-2.3$. We carry out imaging observations and data reduction with Subaru/Hyper Suprime-Cam (HSC). Our total survey area is $\sim12$ deg$^2$ and imaging depths are $25.5-27.0$ mag. Using the imaging data, we select 1,240 and 2,101 LAE candidates at $z=2.2$ and 2.3, respectively. We carry out spectroscopic observations of our LAE candidates and data reduction with Magellan/IMACS to estimate the contamination rate of our LAE candidates. We find that the contamination rate of our sample is low (8%). We stack our LAE candidates with a median stacking method to identify the Ly$\alpha$ halo at $z=2$. We show that the Ly$\alpha$ halo is extended to $\sim200$ kpc at a surface brightness level of $10^{-20}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. Comparing to previous studies, our Ly$\alpha$ halo is more extended at radii of $\sim25-100$ kpc, which is not likely caused by the contamination in our sample but by different redshifts and fields instead. To investigate how central galaxies affect surrounding LAHs, we divide our LAEs into subsamples based on the Ly$\alpha$ luminosity ($L_{\rm Ly\alpha}$), rest-frame Ly$\alpha$ equivalent width (EW$_0$), and UV magnitude (M$_{\rm uv}$). We stack the subsamples and find that higher $L_{\rm Ly\alpha}$, lower EW$_0$, and brighter M$_{\rm uv}$ cause more extended halos. Our results suggest that more massive LAEs generally have more extended Ly$\alpha$ halos.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Daniel Lawther
Marianne Vestergaard
Sandra Raimundo
Jun Yi Koay
Bradley M Peterson
Xiaohui Fan
Dirk Grupe
Smita Mathur
摘要： Mrk 590 is a known changing-look AGN which almost turned off in 2012, and then in 2017 partially re-ignited into a repeat flaring state, unusual for an AGN. Our \emph{Swift} observations since 2013 allow us to characterise the accretion-generated emission and its reprocessing in the central engine of a changing-look AGN. The X-ray and UV variability amplitudes are higher than those typically observed in `steady-state' AGN at similar moderate accretion rates; instead, the variability is similar to that of highly accreting AGN. The unusually strong X-ray to UV correlation suggests that the UV-emitting region is directly illuminated by X-ray outbursts. We find evidence that the X-rays are reprocessed by two UV components, with the dominant one at $\sim$3 days and a faint additional reprocessor at near-zero lag. However, we exclude a significant contribution from diffuse broad line region continuum, known to contribute for bona-fide AGN. A near-zero lag is expected for a standard `lamp-post' disk reprocessing model with a driving continuum source near the black hole. That the overall UV response is dominated by the $\sim$3-day lagged component suggests a complicated reprocessing geometry, with most of the UV continuum not produced in a compact disk, as also found in recent studies of NGC 5548 and NGC 4151. Nonetheless, the observed flares display characteristic timescales of $\sim$100 rest-frame days, consistent with the expected thermal timescale in an accretion disk.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Roberto Decarli
Antonio Pensabene
Tanio Diaz-Santos
Carl Ferkinhoff
Michael A. Strauss
Bram P. Venemans
Fabian Walter
Eduardo Banados
Frank Bertoldi
Xiaohui Fan
Emanuele Paolo Farina
Dominik A. Riechers
Hans-Walter Rix
Ran Wang
摘要： Characterizing the physical conditions (density, temperature, ionization state, metallicity, etc) of the interstellar medium is critical to our understanding of the formation and evolution of galaxies. Here we present a multi-line study of the interstellar medium in the host galaxy of a quasar at z~6.4, i.e., when the universe was 840 Myr old. This galaxy is one of the most active and massive objects emerging from the dark ages, and therefore represents a benchmark for models of the early formation of massive galaxies. We used the Atacama Large Millimeter Array to target an ensemble of tracers of ionized, neutral, and molecular gas, namely the fine-structure lines: [OIII] 88$\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}$), typical of HII regions. The spectral energy distribution of the photoionizing radiation is comparable to that emitted by B-type stars. Star formation also appears to drive the excitation of the molecular medium. We find marginal evidence for outflow-related shocks in the dense molecular phase, but not in other gas phases. This study showcases the power of multi-line investigations in unveiling the properties of the star-forming medium in galaxies at cosmic dawn.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Ryan Endsley
Daniel P. Stark
Jianwei Lyu
Feige Wang
Jinyi Yang
Xiaohui Fan
Renske Smit
Rychard Bouwens
Kevin Hainline
Sander Schouws
摘要： We present band 6 ALMA observations of a heavily-obscured radio-loud ($L_{1.4\ \mathrm{GHz}}=10^{25.4}$ W Hz$^{-1}$) AGN candidate at $z_\mathrm{phot}=6.83\pm0.06$ found in the 1.5 deg$^2$ COSMOS field. The ALMA data reveal detections of exceptionally strong [CII]158$\mu$m ($z_\mathrm{[CII]}=6.8532$) and underlying dust continuum emission from this object (COS-87259), where the [CII] line luminosity, line width, and 158$\mu$m continuum luminosity are comparable to that seen from $z\sim7$ sub-mm galaxies and quasar hosts. The 158$\mu$m continuum detection suggests a total infrared luminosity of $9\times10^{12}$ $L_\odot$ with corresponding very large obscured star formation rate (1300 $M_\odot$/yr) and dust mass ($2\times10^9$ $M_\odot$). The strong break seen between the VIRCam and IRAC photometry perhaps suggests that COS-87259 is an extremely massive reionization era galaxy with $M_\ast\approx1.7\times10^{11}$ $M_\odot$. Moreover, the MIPS, PACS, and SPIRE detections imply that this object harbors an AGN that is heavily obscured ($\tau_{_{\mathrm{9.7\mu m}}}=2.3$) with a bolometric luminosity of approximately $5\times10^{13}$ $L_\odot$. Such a very high AGN luminosity suggests this object is powered by an $\approx$1.6 $\times$ 10$^9$ $M_\odot$ black hole if accreting near the Eddington limit, and is effectively a highly-obscured version of an extremely UV-luminous ($M_{1450}\approx-27.3$) $z\sim7$ quasar. Notably, these $z\sim7$ quasars are an exceedingly rare population ($\sim$0.001 deg$^{-2}$) while COS-87259 was identified over a relatively small field. Future very wide-area surveys with, e.g., Roman and Euclid have the potential to identify many more extremely red yet UV-bright $z\gtrsim7$ objects similar to COS-87259, providing richer insight into the occurrence of intense obscured star formation and supermassive black hole growth among this population.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yali Shao
Ran Wang
Axel Weiss
Jeff Wagg
Chris L. Carilli
Michael A. Strauss
Fabian Walter
Pierre Cox
Xiaohui Fan
Karl M. Menten
Desika Narayanan
Dominik Riechers
Frank Bertoldi
Alain Omont
Linhua Jiang
摘要： We present ALMA sub-kpc- to kpc-scale resolution observations of the [CII], CO(9-8), and OH$^{+}$\,($1_{1}$--$0_{1}$) lines along with their dust continuum emission toward the FIR luminous quasar SDSS J231038.88+185519.7 at $z = 6.0031$. The [CII] brightness follows a flat distribution with a Sersic index of 0.59. The CO(9-8) line and the dust continuum can be fit with an unresolved nuclear component and an extended Sersic component with a Sersic index of ~1. The dust temperature drops with distance from the center. The effective radius of the dust continuum is smaller than that of the line emission and the dust mass surface density, but is consistent with that of the star formation rate surface density. The OH$^{+}$\,($1_{1}$--$0_{1}$) line shows a P-Cygni profile with an absorption, which may indicate an outflow with a neutral gas mass of $(6.2\pm1.2)\times10^{8} M_{\odot}$ along the line of sight. We employed a 3D tilted ring model to fit the [CII] and CO(9-8) data cubes. The two lines are both rotation dominated and trace identical disk geometries and gas motions. We decompose the circular rotation curve measured from the kinematic model fit to the [CII] line into four matter components (black hole, stars, gas, and dark matter). The quasar-starburst system is dominated by baryonic matter inside the central few kiloparsecs. We constrain the black hole mass to be $2.97^{+0.51}_{-0.77}\times 10^{9}\,M_{\odot}$; this is the first time that the dynamical mass of a black hole has been measured at $z\sim6$. A massive stellar component (on the order of $10^{9}\,M_{\odot}$) may have already existed when the Universe was only ~0.93 Gyr old. The relations between the black hole mass and the baryonic mass of this quasar indicate that the central supermassive black hole may have formed before its host galaxy. [Abridged version. Please see the full abstract in the manuscript.]
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Minghao Yue
Jinyi Yang
Xiaohui Fan
Feige Wang
Justin Spilker
Iskren Y. Georgiev
Charles R. Keeton
Katrina C. Litke
Daniel P. Marrone
Fabian Walter
Ran Wang
Xue-Bing Wu
Bram P. Venemans
Ann Zabludoff
摘要： We report ALMA observations of the dust continuum and {\cii} emission of the host galaxy of J0439+1634, a gravitationally lensed quasar at $z=6.5$. Gravitational lensing boosts the source-plane resolution to $\sim0\farcs15$ $(\sim0.8\text{ kpc})$. The lensing model derived from the ALMA data is consistent with the fiducial model in \citet{fan19} based on {\it HST} imaging. The host galaxy of J0439+1634 can be well-fitted by a S\'ersic profile consistent with an exponential disk, both in the far-infrared (FIR) continuum and the {\cii} emission. The overall magnification is $4.53\pm0.05$ for the continuum and $3.44\pm0.05$ for the {\cii} line. The host galaxy of J0439+1634 is a compact ultra-luminous infrared galaxy, with a total star formation rate (SFR) of $1.56\times10^{3}M_\odot/\text{year}$ after correcting for lensing and an effective radius of $0.74$ kpc. The resolved regions in J0439+1634 follow the ``{\cii} deficit," where the {\cii}-to-FIR ratio decreases with FIR surface brightness. The reconstructed velocity field of J0439+1634 appears to be rotation-like. The maximum line-of-sight rotation velocity of 130 km/s at a radius of 2 kpc. However, our data cannot be fit by an axisymmetric thin rotating disk, and the inclination of the rotation axis, $i$, remains unconstrained. We estimate the dynamical mass of the host galaxy to be $7.9\sin^{-2}(i)\times10^{9}M_\odot$. J0439+1634 is likely to have a high gas-mass fraction and an oversized SMBH compared to local relations. The SFR of J0439+1634 reaches the maximum possible values, and the SFR surface density is close to the highest value seen in any star-forming galaxy currently known in the universe.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present spectroscopic confirmation of two new massive galaxy protoclusters at $z=2.24\pm0.02$, BOSS1244 and BOSS1542, traced by groups of Coherently Strong Ly$\alpha$ Absorption (CoSLA) systems imprinted in the absorption spectra of a number of quasars from the SDSS III and identified as overdensities of narrowband-selected H$\alpha$ emitters (HAEs). Using MMT/MMIRS and LBT/LUCI near-infrared (NIR) spectroscopy, we confirm 46 and 36 HAEs in the BOSS1244 and BOSS1542 fields, respectively. BOSS1244 displays a South-West (SW) component at $z=2.230\pm0.002$ and another North-East (NE) component at $z=2.246\pm0.001$ with the line-of-sight velocity dispersions of $405\pm202$ km s$^{-1}$ and $377\pm99$ km s$^{-1}$, respectively. Interestingly, we find that the SW region of BOSS1244 contains two substructures in redshift space, likely merging to form a larger system. In contrast, BOSS1542 exhibits an extended filamentary structure with a low velocity dispersion of $247\pm32$ km s$^{-1}$ at $z=2.241\pm0.001$, providing a direct confirmation of a large-scale cosmic web in the early Universe. The galaxy overdensities $\delta_{\rm g}$ on the scale of 15 cMpc are $22.9\pm4.9$, $10.9\pm2.5$, and $20.5\pm3.9$ for the BOSS1244 SW, BOSS1244 NE, and BOSS1542 filament, respectively. They are the most overdense galaxy protoclusters ($\delta_{\rm g}>20$) discovered to date at $z>2$. These systems are expected to become virialized at $z\sim0$ with a total mass of $M_{\rm SW}=(1.59\pm0.20)\times10^{15}$ $M_{\odot}$, $M_{\rm NE} =(0.83\pm0.11)\times10^{15}$ $M_{\odot}$ and $M_{\rm filament}=(1.42\pm0.18)\times10^{15}$ $M_{\odot}$, respectively. Together with BOSS1441 described in Cai et al. (2017a), these extremely massive overdensities at $z=2-3$ exhibit different morphologies, indicating that they are in different assembly stages in the formation of early galaxy clusters.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present the first results from a new survey for high-redshift
$(z\gtrsim5)$ gravitationally lensed quasars and close quasar pairs. We carry
out candidate selection based on the colors and shapes of objects in public
imaging surveys, then conduct follow-up observations to confirm the nature of
high-priority candidates. In this paper, we report the discoveries of
J0025--0145 ($z=5.07$) which we identify as an {intermediately-lensed quasar,
and J2329--0522 ($z=4.85$) which is a kpc-scale close quasar pair. The {\em
Hubble Space Telescope (HST)} image of J0025--0145 shows a foreground lensing
galaxy located $0\farcs6$ away from the quasar. However, J0025--0145 does not
exhibit multiple lensed images of the quasar, and we identify J0025--0145 as an
intermediate lensing system (a lensing system that is not multiply imaged but
has a significant magnification). The spectrum of J0025--0145 implies an
extreme Eddington ratio if the quasar luminosity is intrinsic, which could be
explained by a large lensing magnification. The {\em HST} image of J0025--0145
also indicates a tentative detection of the quasar host galaxy in rest-frame
UV, illustrating the power of lensing magnification and distortion in studies
of high-redshift quasar host galaxies. J2329--0522 consists of two resolved
components with significantly different spectral properties, and a lack of
lensing galaxy detection under sub-arcsecond seeing. We identify it as a close
quasar pair, which is the highest confirmed kpc-scale quasar pair to date. We
also report four lensed quasars and quasar pairs at $2
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a well-designed sample of more than 1000 type 1 quasars at
$3.50.5$. The
evolution of the QLFs from $z\sim5$ to $3.5$ can be described by a pure density
evolution model ($\propto10^{kz}$) and the parameter $k$ is similar to that at
$5
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jinyi Yang
Xiaohui Fan
Feige Wang
Giorgio Lanzuisi
Riccardo Nanni
Massimo Cappi
George Chartas
Mauro Dadina
Roberto Decarli
Xiangyu Jin
Charles R. Keeton
Bram P. Venemans
Fabian Walter
Ran Wang
Xue-Bing Wu
Minghao Yue
Ann Zabludoff
摘要： We report X-ray observations of the most distant known gravitationally lensed quasar, J0439+1634 at $z=6.52$, which is also a broad absorption line (BAL) quasar, using the XMM-Newton Observatory. With a 130 ks exposure, the quasar is significantly detected as a point source at the optical position with a total of 358$^{+19}_{-19}$ net counts using the EPIC instrument. By fitting a power-law plus Galactic absorption model to the observed spectra, we obtain a spectral slope of $\Gamma=1.45^{+0.10}_{-0.09}$. The derived optical-to-X-ray spectral slope $\alpha_{\rm{ox}}$ is $-2.07^{+0.01}_{-0.01}$, suggesting that the X-ray emission of J0439+1634 is weaker by a factor of 18 than the expectation based on its 2500 Angstrom luminosity and the average $\alpha_{\rm{ox}}$ vs. luminosity relationship. This is the first time that an X-ray weak BAL quasar at $z>6$ has been observed spectroscopically. Its X-ray weakness is consistent with the properties of BAL quasars at lower redshift. By fitting a model including an intrinsic absorption component, we obtain intrinsic column densities of $N_{\rm{H}}=2.8^{+0.7}_{-0.6}\times10^{23}\,\rm{cm}^{-2}$ and $N_{\rm{H}}= 4.3^{+1.8}_{-1.5}\times10^{23}\,\rm{cm}^{-2}$, assuming a fixed $\Gamma$ of 1.9 and a free $\Gamma$, respectively. The intrinsic rest-frame 2--10 keV luminosity is derived as $(9.4-15.1)\times10^{43}\,\rm{erg\,s}^{-1}$, after correcting for lensing magnification ($\mu=51.3$). The absorbed power-law model fitting indicates that J0439+1634 is the highest redshift obscured quasar with a direct measurement of the absorbing column density. The intrinsic high column density absorption can reduce the X-ray luminosity by a factor of $3-7$, which also indicates that this quasar could be a candidate of intrinsically X-ray weak quasar.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shu Wang
Linhua Jiang
Yue Shen
Luis C. Ho
Marianne Vestergaard
Eduardo Banados
Chris J. Willott
Jin Wu
Siwei Zou
Jinyi Yang
Feige Wang
Xiaohui Fan
Xue-Bing Wu
摘要： Broad line regions (BLRs) in high-redshift quasars provide crucial
information of chemical enrichment in the early universe. Here we present a
study of BLR metallicities in 33 quasars at redshift $5.7
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yunjing Wu
Zheng Cai
Marcel Neeleman
Kristian Finlator
Shiwu Zhang
J. Xavier Prochaska
Ran Wang
Bjorn H.
C Emonts
Xiaohui Fan
Laura C. Keating
Feige Wang
Jinyi Yang
Joseph F. Hennawi
Junxian Wang
摘要： The physical and chemical properties of the circumgalactic medium (CGM) at $z\gtrsim6$ have been studied successfully through the absorption in the spectra of background Quasi-Stellar Objects (QSOs). One of the most crucial questions is to investigate the nature and location of the source galaxies that give rise to these early metal absorbers. Theoretical models suggest that momentum-driven outflows from typical star-forming galaxies can eject metals into the CGM and the intergalactic medium (IGM) at z=5-6. Deep, dedicated surveys have searched for Ly$\alpha$ emission associated with strong CIV absorbers at $z\approx 6$, but only a few Ly$\alpha$ emitter candidates have been detected. Interpreting these detections is moreover ambiguous because Ly$\alpha$ is a resonant line, raising the need for complementary techniques for detecting absorbers' host galaxies. Here, using Atacama Large Millimeter Array (ALMA), we report a [C II] 158$\mu$m emitter associated with a strong low-ionization absorber, OI, at $z=5.978$. The projected impact parameter between OI and [C II] emitter is 20.0 kpc. The measured [C II] luminosity is $7.0\times 10^7$ solar luminosities. Further analysis indicates that strong OI absorbers may reside in the circumgalactic medium of massive halos one to two orders of magnitude more massive than expected values.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The observed lensed fraction of high-redshift quasars $(\sim0.2\%)$ is significantly lower than previous theoretical predictions $(\gtrsim4\%)$. We revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (VDFs) and explore a wide range of quasar luminosity function (QLF) parameters. We use both analytical methods and mock catalogs which give consistent results. For ordinary QLF parameters and the depth of current high-redshift quasar surveys $(m_z\lesssim22)$, our model suggests a multiply-imaged fraction of $F_\text{multi}\sim 0.4\%-0.8\%$. The predicted lensed fraction is $\sim1\%-6\%$ for the brightest $z_s\sim6$ quasars $(m_z\lesssim19)$, depending on the QLF. The systematic uncertainties of the predicted lensed fraction in previous models can be as large as $2-4$ times and are dominated by the VDF. Applying VDFs from recent measurements decreases the predicted lensed fraction and relieves the tension between observations and theoretical models. Given the depth of current imaging surveys, there are $\sim15$ lensed quasars at $z_s>5.5$ detectable over the sky. Upcoming sky surveys like the LSST survey and the {\em Euclid} survey will find several tens of lensed quasars at this redshift range.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiaojing Lin
Zheng Cai
Siwei Zou
Zihao Li
Zuyi Chen
Fuyan Bian
Fengwu Sun
Yiping Shu
Yunjing Wu
Mingyu Li
Jianan Li
Xiaohui Fan
J. Xavier Prochaska
Daniel Schaerer
Stephane Charlot
Daniel Espada
Miroslava Dessauges-Zavadsky
Eiichi Egami
Daniel Stark
Kirsten K. Knudsen
摘要： Direct observations of low-mass, low-metallicity galaxies at $z\gtrsim4$ provide an indispensable opportunity for detailed inspection of the ionization radiation, gas flow, and metal enrichment in sources similar to those that reionized the Universe. Combining the James Webb Space Telescope (JWST), VLT/MUSE, and ALMA, we present detailed observations of a strongly lensed, low-mass ($\approx 10^{7.6}$ ${\rm M}_\odot$) galaxy at $z=3.98$ (also see Vanzella et al. 2022). We identify strong narrow nebular emission, including CIV $\lambda\lambda1548,1550$, HeII $\lambda1640$, OIII] $\lambda\lambda1661,1666$, [NeIII] $\lambda3868$, [OII] $\lambda3727$, and Balmer series of Hydrogen from this galaxy, indicating a metal-poor HII region ($\lesssim 0.12\ {\rm Z}_\odot$) powered by massive stars. Further, we detect a metal-enriched damped Ly$\alpha$ system (DLA) associated with the galaxy with the HI column density of $N_{\rm{HI}}\approx 10^{21.8}$ cm$^{-2}$. The metallicity of the associated DLA may reach the super solar metallicity (${\gtrsim Z}_\odot$). Moreover, thanks to JWST and gravitational lensing, we present the resolved UV slope ($\beta$) map at the spatial resolution of $\approx 100$ pc at $z=4$, with steep UV slopes reaching $\beta \approx -2.5$ around three star-forming clumps. Combining with low-redshift analogs, our observations suggest that low-mass, low-metallicity galaxies, which dominate reionization, could be surrounded by a high covering fraction of the metal-enriched, neutral-gaseous clouds. This implies that the metal enrichment of low-mass galaxies is highly efficient, and further support that in low-mass galaxies, only a small fraction of ionizing radiation can escape through the interstellar or circumgalactic channels with low column-density neutral gas.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Quasars at cosmic dawn provide powerful probes of the formation and growth of the earliest supermassive black holes (SMBHs) in the universe, their connections to galaxy and structure formation, and the evolution of the intergalactic medium (IGM) at the epoch of reionization (EoR). Hundreds of quasars have been discovered in the first billion years of cosmic history, with the quasar redshift frontier extended to z~7.6. Observations of quasars at cosmic dawn show that: (1) The number density of luminous quasars declines exponentially at z>5, suggesting that the earliest quasars emerge at z~10; the lack of strong evolution in their average spectral energy distribution indicates a rapid buildup of the AGN environment. (2) Billion-solar-mass BHs already exist at z>7.5; they must form and grow in less than 700 Myr, by a combination of massive early BH seeds with highly efficient and sustained accretion. (3) The rapid quasar growth is accompanied by strong star formation and feedback activity in their host galaxies, which show diverse morphological and kinetic properties, with typical dynamical mass of lower than that implied by the local BH/galaxy scaling relations. (4) HI absorption in quasar spectra probes the tail end of cosmic reionization at z~5.3-6, and indicates the EoR midpoint at 6.9 < z < 7.6 with large spatial fluctuations in IGM ionization. Observations of heavy element absorption lines suggest that the circumgalactic medium also experiences evolution in its ionization structure and metal enrichment during the EoR.
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