The Host-Galaxy Properties of Type 1 Versus Type 2 Active Galactic Nuclei

Abstract

The unified model of active galactic nuclei (AGNs) proposes that different AGN optical spectral types are caused by different viewing angles with respect to an obscuring 'torus'. Therefore, this model predicts that type 1 and type 2 AGNs should have similar host-galaxy properties. We investigate this prediction with 2463 X-ray selected AGNs in the COSMOS field. We divide our sample into type 1 and type 2 AGNs based on their spectra, morphologies, and variability. We derive their host-galaxy stellar masses ($M_{\star }$) through SED fitting, and find that the host $M_{\star }$ of type 1 AGNs tend to be slightly smaller than those of type 2 AGNs by $\Delta \overline{\log M_{\star }}\approx 0.2\mathrm{dex}$ ($\approx 4\sigma$ significance). Besides deriving star-formation rates (SFRs) from SED fitting, we also utilize far-infrared (FIR) photometry and a stacking method to obtain FIR-based SFRs. We find that the SFRs of type 1 and type 2 sources are similar once their redshifts and X-ray luminosities are controlled. We also investigate cosmic environment, and find that the surface number densities (sub-Mpc) and cosmic-web environments ($\approx 1\text{–}10$~Mpc) are similar for both populations. In summary, our analyses show that the host galaxies of type 1 and type 2 AGNs have similar SFR and cosmic environment in general, but the former tend to have lower $M_{\star }$ than the latter. The difference in $M_{\star }$ indicates that the AGN unification model is not strictly correct and both host galaxy and torus may contribute to the optical obscuration of AGNs.

16 pages, 10 figures; accepted for publication in ApJ

References in corpus (26)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements
• Photometric redshift and classification for the XMM-COSMOS sources
• Cosmic X-ray Surveys of Distant Active Galaxies: The Demographics, Physics, and Ecology of Growing Supermassive Black Holes
• The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
• The XMM-Newton wide-field survey in the COSMOS field. The point-like X-ray source catalogue
• Constraining the properties of AGN host galaxies with Spectral Energy Distribution modeling
• The Constant Average Relationship between Dust-obscured Star Formation and Stellar Mass from $z=0$ to $z=2.5$
• A consistent measure of the merger histories of massive galaxies using close-pair statistics I: Major mergers at $z<3.5$
• The spatial clustering of X-ray selected AGN in the XMM-COSMOS field
• The FMOS-COSMOS survey of star-forming galaxies at $z\sim 1.6$ VI: Redshift and emission-line catalog and basic properties of star-forming galaxies
• The mean star formation rates of unobscured QSOs: searching for evidence of suppressed or enhanced star formation
• Galaxy gas as obscurer: II. Separating the galaxy-scale and nuclear obscurers of Active Galactic Nuclei
• Black-Hole Growth is Mainly Linked to Host-Galaxy Stellar Mass rather than Star Formation Rate
• The Angular Clustering of Infrared-Selected Obscured and Unobscured Quasars
• Evident black hole-bulge coevolution in the distant universe
• Obscuring Active Galactic Nuclei with Nuclear Starburst Disks
• Clustering properties of moderate luminosity X-ray selected Type 1 and Type 2 AGN at z~3
• Galaxy gas as obscurer: I. GRBs x-ray galaxies and find a N_H ~ M* relation
• The Chandra Deep Fields: Lifting the Veil on Distant Active Galactic Nuclei and X-Ray Emitting Galaxies
• Galaxy Formation as a Cosmological Tool. I: The Galaxy Merger History as a Measure of Cosmological Parameters
• The different neighbours around Type-1 and Type-2 active galactic nuclei
• Dust attenuation up to z~2 in the AKARI North Ecliptic Pole Deep Field
• AGN luminosity and stellar age -- two missing ingredients for AGN unification as seen with iPTF supernovae

Cited by in corpus (20)

• X-CIGALE: fitting AGN/galaxy SEDs from X-ray to infrared
• Galaxy properties of type 1 and 2 X-ray selected AGN and comparison among different classification criteria
• Polar dust obscuration in broad-line active galaxies from the XMM-XXL field
• Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material
• The relation between AGN type and host galaxy properties
• The role of AGN and its obscuration on the position of the host galaxy relative to Main Sequence
• Value Added Catalog of physical properties of more than 1.3 million galaxies from the DESI Survey
• XXL-HSC: The link between AGN activity and star formation in the Early Universe ($z⩾3.5$)
• X-ray properties of dust-obscured galaxies with broad optical/UV emission lines
• Genuine Retrieval of the AGN Host Stellar Population (GRAHSP)
• Comparing the host galaxy ages of X-ray selected AGN in COSMOS: Obscured AGN are associated with older galaxies
• Oxygen abundances in the narrow line regions of Seyfert galaxies and the metallicity-luminosity relation
• The Most Obscured AGNs in the XMM-SERVS Fields
• Systematic research of low redshift optically selected SDSS Type-2 AGN but with apparent long-term optical variabilities from Catalina Sky Survey, I: data sample and basic results
• Efficient Analysis Routines for Single and Double Peaked Type 2 AGN Spectra
• Extinction and AGN over host galaxy contrast effects on the optical spectroscopic classification of AGN
• A new approach to constraining properties of AGN host galaxies by combining image and SED decomposition: testing upon the MBH-M* relation
• AGN obscuration in optical and X-rays: Host properties and the interplay of nuclear and galactic gas and dust in a combined SDSS-XMM sample
• Obscured and unobscured X-ray AGNs I: Host galaxy properties
• BASS. XLIV. Morphological preferences of local hard X-ray selected AGN