分类： 天文学 >> 天文学 提交时间： 2023-02-19
Valentina Tardugno Poleo
Steven Finkelstein
Gene C. K. Leung
Erin Mentuch Cooper
Karl Gebhardt
Daniel Farrow
Eric Gawiser
Gregory Zeimann
Donald Schneider
Leah Morabito
Daniel Mock
Chenxu Liu
摘要： We used data from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) to study the incidence of AGN in continuum-selected galaxies at $z\sim3$. From optical and infrared imaging in the 24 deg$^{2}$ Spitzer HETDEX Exploratory Large Area (SHELA) survey, we constructed a sample of photometric-redshift selected $z\sim3$ galaxies. We extracted HETDEX spectra at the position of 716 of these sources and used machine learning methods to identify those which exhibited AGN-like features. The dimensionality of the spectra was reduced using an autoencoder, and the latent space was visualized through t-distributed stochastic neighbor embedding (t-SNE). Gaussian mixture models were employed to cluster the encoded data and a labeled dataset was used to label each cluster as either AGN, stars, high-redshift galaxies, or low-redshift galaxies. Our photometric redshift (photo-z) sample was labeled with an estimated $92\%$ overall accuracy, an AGN accuracy of $83\%$, and an AGN contamination of $5\%$. The number of identified AGN was used to measure an AGN fraction for different magnitude bins. The UV absolute magnitude where the AGN fraction reaches $50\%$ is $M_{UV} = -23.8$. When combined with results in the literature, our measurements of AGN fraction imply that the bright end of the galaxy luminosity function exhibits a power-law rather than exponential decline, with a relatively shallow faint-end slope for the $z\sim3$ AGN luminosity function.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Dongsheng Sun
Ken Mawatari
Ouchi Masami
Yoshiaki Ono
Hidenobu Yajima
Yechi Zhang
Makito Abe
William P. Bowman
Erin Mentuch Cooper
Dustin Davis
Daniel J. Farrow
Karl Gebhardt
Gary J. Hill
Chenxu Liu
Donald P. Schneider
摘要： We present cosmological-scale 3-dimensional (3D) neutral hydrogen ({\sc Hi}) tomographic maps at $z=2-3$ over a total of 837 deg$^2$ in two blank fields that are developed with Ly$\alpha$ forest absorptions of 14,736 background Sloan Digital Sky Survey (SDSS) quasars at $z$=2.08-3.67. Using the tomographic maps, we investigate the large-scale ($\gtrsim 10$ $h^{-1}$cMpc) average {\sc Hi} radial profiles and two-direction profiles of the line-of-sight (LoS) and transverse (TS) directions around galaxies and AGN at $z=2-3$ identified by the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX) and SDSS surveys, respectively.The peak of the {\sc Hi} radial profile around galaxies is lower than the one around AGN, suggesting that the dark-matter halos of galaxies are less massive on average than those of AGN. The LoS profile of AGN is narrower than the TS profile, indicating the Kaiser effect. There exist ionized outskirts at $\gtrsim 30$ $h^{-1}$cMpc beyond {\sc Hi} rich structures of galaxies and AGN found in the LoS profiles that can be explained by the influence of high energy photons propagating over a long distance. Our findings indicate that the {\sc Hi} radial profile of AGN has transitions from proximity zones ($\lesssim$ a few $h^{-1}$cMpc) to the {\sc Hi} rich structures ($\sim 1-30$ $h^{-1}$cMpc) and the ionized outskirts ($\gtrsim 30$ $h^{-1}$cMpc). Although there is no significant dependence of AGN types (type-1 vs. type-2) on the {\sc Hi} profiles, the peaks of the radial profiles anti-correlate with AGN luminosities, suggesting that AGN's ionization effects are stronger than the gas mass differences.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chenxu Liu
Karl Gebhardt
Wolfram Kollatschny
Robin Ciardullo
Erin Mentuch Cooper
Dustin Davis
Daniel J. Farrow
Steven L. Finkelstein
Eric Gawiser
Caryl Gronwall
Gary J. Hill
Lindsay House
Donald P. Schneider
Tanya Urrutia
Gregory R. Zeimann
摘要： We report an Active Galactic Nucleus (AGN) with extremely high equivalent width (EW), EW(LyA+NV,rest)>921 AA in the rest-frame, at z~2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) as a representative case of the high EW AGN population. The continuum level is a non-detection in the HETDEX spectrum, thus the measured EW is a lower limit. The source is detected with significant emission lines (>7sigma) at LyA+NV, CIV, and moderate emission line (~4sigma) at HeII within the wavelength coverage of HETDEX (3500 AA - 5500 AA). The r-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit of r=25.12 at 5sigma. The LyA emission line spans a clearly resolved region of ~10 arcsec (85 kpc) in diameter. The LyA line profile is strongly double peaked. The spectral decomposed blue gas and red gas Ly$\alpha$ emission are separated by ~1.2 arcsec (10.1 kpc) with a line-of-sight velocity offset of ~1100 km/s. This source is probably an obscured AGN with powerful winds.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yechi Zhang
Masami Ouchi
Karl Gebhardt
Chenxu Liu
Yuichi Harikane
Erin Mentuch Cooper
Dustin Davis
Daniel J. Farrow
Eric Gawiser
Gary J. Hill
Wolfram Kollatschny
Yoshiaki Ono
Donald P. Schneider
Steven L. Finkelstein
Caryl Gronwall
Shardha Jogee
Mirko Krumpe
摘要： We investigate the stellar mass - black hole mass ($\mathcal{M}_*-\mathcal{M}_\mathrm{BH}$) relation with type 1 AGN down to $\mathcal{M}_\mathrm{BH}=10^7 M_\odot$, corresponding to a $\simeq -21$ absolute magnitude in rest-frame ultraviolet (UV), at $z = 2-2.5$. Exploiting the deep and large-area spectroscopic survey of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), we identify 66 type 1 AGN with $\mathcal{M}_\mathrm{BH}$ ranging from $10^7$ to $10^{10} M_\odot$ that are measured with single-epoch virial method using C{\sc iv} emission lines detected in the HETDEX spectra. $\mathcal{M}_*$ of the host galaxies are estimated from optical to near-infrared photometric data taken with Spitzer, WISE, and ground-based 4-8m class telescopes by CIGALE SED fitting. We further assess the validity of SED fitting in two cases by host-nuclear decomposition performed through surface brightness profile fitting on spatially-resolved host galaxies with JWST/NIRCam CEERS data. We obtain the $\mathcal{M}_*-\mathcal{M}_\mathrm{BH}$ relation covering the unexplored low-mass ranges of $\mathcal{M}_\mathrm{BH}~\sim~10^7-10^8~M_\odot$, and conduct forward modelling to fully account for the selection biases and observational uncertainties. The intrinsic $\mathcal{M}_*-\mathcal{M}_\mathrm{BH}$ relation at $z\sim 2$ has a moderate positive offset of $0.52\pm0.14$~dex from the local relation, suggestive of more efficient black hole growth at higher redshift even in the low-mass regime of $\mathcal{M}_\mathrm{BH}~\sim~10^7-10^8~M_\odot$. Our $\mathcal{M}_*-\mathcal{M}_\mathrm{BH}$ relation is inconsistent with the $\mathcal{M}_\mathrm{BH}$ suppression at the low-$\mathcal{M}_*$ regime predicted by recent hydrodynamic simulations at a $98\%$ confidence level, suggesting that feedback in the low-mass systems may be weaker than those produced in hydrodynamic simulations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yechi Zhang
Masami Ouchi
Karl Gebhardt
Erin Mentuch Cooper
Chenxu Liu
Dustin Davis
Donghui Jeong
Daniel J. Farrow
Steven L. Finkelstein
Eric Gawiser
Gary J. Hill
Yuichi Harikane
Ryota Kakuma
Viviana Acquaviva
Caitlin M. Casey
Maximilian Fabricius
Ulrich Hopp
Matt J. Jarvis
Martin Landriau
Ken Mawatari
摘要： We present Ly$\alpha$ and ultraviolet-continuum (UV) luminosity functions (LFs) of galaxies and active galactic nuclei (AGN) at $z=2.0-3.5$ determined by the un-targetted optical spectroscopic survey of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in $11.4$ deg$^2$ of fiber-spectra sky coverage, obtaining $18320$ galaxies spectroscopically identified with Ly$\alpha$ emission, $2126$ of which host type 1 AGN showing broad (FWHM$~>1000$ km s$^{-1}$) Ly$\alpha$ emission lines. We derive the Ly$\alpha$ (UV) LF over 2 orders of magnitude covering bright galaxies and AGN in $\log L_\mathrm{Ly\alpha}/\mathrm{[erg~s^{-1}]}=43.3-45.5$ ($-27-21$) type 1 AGN increases from $z\sim2$ to $z\sim0$ as opposed to the evolution of bright ($M_\mathrm{UV}<-21$) type 1 AGN, suggesting the AGN downsizing in the rest-frame UV luminosity.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chenxu Liu
Karl Gebhardt
Wolfram Kollatschny
Robin Ciardullo
Erin Mentuch Cooper
Dustin Davis
Daniel J. Farrow
Steven L. Finkelstein
Eric Gawiser
Caryl Gronwall
Gary J. Hill
Lindsay House
Donald P. Schneider
Tanya Urrutia
Gregory R. Zeimann
摘要： We report an Active Galactic Nucleus (AGN) with extremely high equivalent width (EW), EW(LyA+NV,rest)>921 AA in the rest-frame, at z~2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) as a representative case of the high EW AGN population. The continuum level is a non-detection in the HETDEX spectrum, thus the measured EW is a lower limit. The source is detected with significant emission lines (>7sigma) at LyA+NV, CIV, and moderate emission line (~4sigma) at HeII within the wavelength coverage of HETDEX (3500 AA - 5500 AA). The r-band magnitude is 24.57 from the Hyper Suprime-Cam-HETDEX joint survey with a detection limit of r=25.12 at 5sigma. The LyA emission line spans a clearly resolved region of ~10 arcsec (85 kpc) in diameter. The LyA line profile is strongly double peaked. The spectral decomposed blue gas and red gas Ly$\alpha$ emission are separated by ~1.2 arcsec (10.1 kpc) with a line-of-sight velocity offset of ~1100 km/s. This source is probably an obscured AGN with powerful winds.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Dustin Davis
Karl Gebhardt
Erin Mentuch Cooper
Robin Ciardullo
Maximilian Fabricius
Daniel J. Farrow
John J. Feldmeier
Steven L. Finkelstein
Eric Gawiser
Caryl Gronwall
Gary J. Hill
Ulrich Hopp
Lindsay R. House
Donghui Jeong
Wolfram Kollatschny
Eiichiro Komatsu
Martin Landriau
Chenxu Liu
Shun Saito
Sarah Tuttle
摘要： The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted spectroscopic survey that aims to measure the expansion rate of the Universe at $z \sim 2.4$ to 1% precision for both $H(z)$ and $D_A(z)$. HETDEX is in the process of mapping in excess of one million Lyman Alpha emitting (LAE) galaxies and a similar number of lower-z galaxies as a tracer of the large-scale structure. The success of the measurement is predicated on the post-observation separation of galaxies with Ly$\alpha$ emission from the lower-$z$ interloping galaxies, primarily [OII], with low contamination and high recovery rates. The Emission Line eXplorer (ELiXer) is the principal classification tool for HETDEX, providing a tunable balance between contamination and completeness as dictated by science needs. By combining multiple selection criteria, ELiXer improves upon the 20 Angstrom rest-frame equivalent width cut commonly used to distinguish LAEs from lower-$z$ [OII] emitting galaxies. Despite a spectral resolving power, R $\sim800$, that cannot resolve the [OII] doublet, we demonstrate the ability to distinguish LAEs from foreground galaxies with 98.1% accuracy. We estimate a contamination rate of Ly$\alpha$ by [OII] of 1.2% and a Ly$\alpha$ recovery rate of 99.1% using the default ELiXer configuration. These rates meet the HETDEX science requirements.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chenxu Liu
Karl Gebhardt
Erin Mentuch Cooper
Yechi Zhang
Donald P. Schneider
Robin Ciardullo
Dustin Davis
Daniel J. Farrow
Steven L. Finkelstein
Caryl Gronwall
Gary J. Hill
Lindsay House
Donghui Jeong
Wolfram Kollatschny
Maja Lujan Niemeyer
Sarah Tuttle
摘要： We present the LyA emission line luminosity function (LF) of the Active
Galactic Nuclei (AGN) in the first release of the Hobby-Eberly Telescope Dark
Energy Experiment Survey (HETDEX) AGN catalog (Liu et al. 2022, Paper I). The
AGN are selected either by emission-line pairs characteristic of AGN or by
single broad emission line, free of any photometric pre-selections
(magnitude/color/morphology). The sample consists of 2,346 AGN spanning
1.885\sigma$ confidence at r~26 in the deepest
$r$-band images we have searched. The LyA line luminosity ranges from ~10^42.3
to ~10^45.9 erg s^-1. Our LyA LF shows a turnover luminosity with opposite
slopes on the bright end and the faint end: The space density is highest at
L_LyA^*=10^43.4 erg s^-1.
We explore the evolution of the AGN LF over a broader redshift range
(0.8
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Erin Mentuch Cooper
Karl Gebhardt
Dustin Davis
Daniel J. Farrow
Chenxu Liu
Gregory Zeimann
Robin Ciardullo
John J. Feldmeier
Niv Drory
Donghui Jeong
Barbara Benda
William P. Bowman
Michael Boylan-Kolchin
Oscar A. Chavez Ortiz
Maya H. Debski
Mona Dentler
Maximilian Fabricius
Rameen Farooq
Steven L. Finkelstein
Eric Gawiser
摘要： We present the first publicly released catalog of sources obtained from the
Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). HETDEX is an integral
field spectroscopic survey designed to measure the Hubble expansion parameter
and angular diameter distance at 1.88
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chenxu Liu
Karl Gebhardt
Erin Mentuch Cooper
Dustin Davis
Donald P. Schneider
Robin Ciardullo
Daniel J. Farrow
Steven L. Finkelstein
Caryl Gronwall
Yuchen Guo
Gary J. Hill
Lindsay House
Donghui Jeong
Shardha Jogee
Wolfram Kollatschny
Mirko Krumpe
Martin Landriau
Oscar A Chavez Ortiz
Yechi Zhang
摘要： We present the first Active Galactic Nuclei (AGN) catalog in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) observed between January 2017 and June 2020. HETDEX is an ongoing spectroscopic survey with no pre-selection based on magnitudes, colors or morphologies, enabling us to select AGN based on their spectral features. Both luminous quasars and low-luminosity Seyferts are found in our catalog. AGN candidates are selected with at least two significant AGN emission lines, such as the LyA and CIV line pair, or with single broad emission lines (FWHM > 1000 km/s). Each source is further confirmed by visual inspections. This catalog contains 5,322 AGN, covering an effective sky coverage of 30.61 deg^2. A total of 3,733 of these AGN have secure redshifts, and we provide redshift estimates for the remaining 1,589 single broad-line AGN with no cross matched spectral redshifts from SDSS DR14Q. The redshift range of the AGN catalog is 0.25 22.5, and 2.6% reaching the detection limit at r ~ 26 mag of the deepest imaging surveys we searched. We also provide a composite spectrum of the AGN sample covering 700 AA - 4400 AA.
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