First HETDEX Spectroscopic Determinations of Ly$\alpha$ and UV Luminosity Functions at $z=2-3$: Bridging a Gap Between Faint AGN and Bright Galaxies

Abstract

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 $\log L_{\mathrm{Ly}\alpha }/[\mathrm{erg}{\mathrm{s}}^{-1}]=43.3-45.5$ ($-27<M_{\mathrm{UV}}<-20$) by the $1/V_{\max }$ estimator. Our results reveal the bright-end hump of the Ly$\alpha$ LF is composed of type 1 AGN. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be ${\alpha }_{\mathrm{Sch}}=-1.70_{-0.14}^{+0.13}$, which indicates ${\alpha }_{\mathrm{Sch}}$ steepens from $z=2-3$ towards high redshift. Our UV LF agrees well with previous AGN UV LFs, and extends to faint-AGN and bright-galaxy regimes. The number fraction of Ly$\alpha$-emitting objects ($X_{\mathrm{LAE}}$) increases from $M_{\mathrm{UV}}^{\ast }\sim -21$ to bright magnitude due to the contribution of type 1 AGN, while previous studies claim that $X_{\mathrm{Ly}\alpha }$ decreases from faint magnitude to $M_{\mathrm{UV}}^{\ast }$, suggesting a valley in the $X_{\mathrm{Ly}\alpha }-$magnitude relation at $M_{\mathrm{UV}}^{\ast }$. Comparing our UV LF of type 1 AGN at $z=2-3$ with those at $z=0$, we find that the number density of faint ($M_{\mathrm{UV}}>-21$) type 1 AGN increases from $z\sim 2$ to $z\sim 0$ as opposed to the evolution of bright ($M_{\mathrm{UV}}<-21$) type 1 AGN, suggesting the AGN downsizing in the rest-frame UV luminosity.

27 pages, 19 figures, accepted for publication in ApJ

References in corpus (25)

• A Catalog of Quasar Properties from SDSS DR7
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• An Observational Determination of the Bolometric Quasar Luminosity Function
• The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
• The MOSFIRE Deep Evolution Field (MOSDEF) Survey: Rest-Frame Optical Spectroscopy for ~1500 H-Selected Galaxies at 1.37 < z < 3.8
• The End of the Reionization Epoch Probed by Ly-alpha Emitters at z=6.5 in the Subaru Deep Field
• Absorption Properties and Evolution of Active Galactic Nuclei
• Ly-alpha Emission-Line Galaxies at z = 3.1 in the Extended Chandra Deep Field South
• The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift
• The first ultraviolet quasar stacked spectrum at z=2.4 from WFC3
• Observations of the Lyman-$\alpha$ Universe
• The VVDS type-1 AGN sample: The faint end of the luminosity function
• Effects of Dust Geometry in Lyman Alpha Galaxies at z = 4.4
• The CALYMHA survey: Lya luminosity function and global escape fraction of Lya photons at z=2.23
• Deficiency of large equivalent width Lyman-alpha emission in luminous Lyman break galaxies at z~5-6?
• The MUSE Hubble Ultra Deep Field Survey VI: The Faint-End of the Lya Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation
• The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX): Description and Early Pilot Survey Results
• Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy
• Onset of Cosmic Reionization: Evidence of An Ionized Bubble Merely 680 Myrs after the Big Bang
• The physical properties of Lyalpha emitting galaxies: not just primeval galaxies?
• Low accretion rates at the AGN cosmic downsizing epoch
• Connecting Faint End Slopes of the Lyman-$\alpha$ emitter and Lyman-break Galaxy Luminosity Functions
• A Faint Flux-Limited Lyman Alpha Emitter Sample at $z\sim 0.3$
• Correcting correlation functions for redshift-dependent interloper contamination
• Replicated Spectrographs in Astronomy

Cited by in corpus (15)

• HETDEX Public Source Catalog 1: 220K Sources Including Over 50K Lyman Alpha Emitters from an Untargeted Wide-area Spectroscopic Survey
• Surface Brightness Profile of Lyman-$\alpha$ Halos out to 320 kpc in HETDEX
• Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies
• The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) I. Sample selection
• The Stellar Mass - Black Hole Mass Relation at $z\sim 2$ Down to ${\mathcal{M}}_{\mathrm{BH}}\sim 10^7{M}_{\odot }$ Determined by HETDEX
• Median Surface Brightness Profiles of Lyman-$\alpha$ Haloes in the MUSE Extremely Deep Field
• The UV luminosity function at 0.6 < z < 1 from UVCANDELS
• Identifying Active Galactic Nuclei at $z\sim 3$ from the HETDEX Survey Using Machine Learning
• The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) II. Luminosity Function
• Revisiting the Emission Line Source Detection Problem in Integral Field Spectroscopic Data
• The miniJPAS & J-NEP surveys: Identification and characterization of the Ly$\alpha$ Emitter population and the Ly$\alpha$ Luminosity Function
• The PAU Survey: The quasar UV and Ly$\alpha$ luminosity functions at $2.7<z<5.3$
• Searching for Supernovae in HETDEX Data Release 3
• Cosmological-Scale Lyman-alpha Forest Absorption Around Galaxies and AGN Probed with the HETDEX and SDSS Spectroscopic Data
• Bayesian luminosity function estimation in multi-depth datasets with selection effects: A case study for $3<z<5$ Lyman $\alpha$ emitters