MID-INFRARED SELECTION OF ACTIVE GALACTIC NUCLEI WITH THE WIDE-FIELD INFRARED SURVEY EXPLORER. II. PROPERTIES OF WISE-SELECTED ACTIVE GALACTIC NUCLEI IN THE NDWFS BOÖTES FIELD

By R. Assef, Daniel Stern, C. Kochanek, A. Blain, M. Brodwin, Michael J. I. Brown, E. Donoso, P. Eisenhardt, B. Jannuzi, T. Jarrett and 4 more. 2012

258 citations recorded by the source corpus.

Stern et al. presented a study of Wide-field Infrared Survey Explorer (WISE) selection of active galactic nuclei (AGNs) in the 2 deg2 COSMOS field, finding that a simple criterion W1–W2 ⩾ 0.8 provides a highly reliable and complete AGN sample for W2 < 15.05, where the W1 and W2 passbands are centered at 3.4 μm and 4.6 μm, respectively. Here we extend this study using the larger 9 deg2 NOAO Deep Wide-Field Survey Boötes field which also has considerably deeper WISE observations than the COSMOS field, and find that this simple color cut significantly loses reliability at fainter fluxes. We define a modified selection criterion combining the W1−W2 color and the W2 magnitude to provide highly reliable or highly complete AGN samples for fainter WISE sources. In particular, we define a color–magnitude cut that finds 130 ± 4 deg−2 AGN candidates for W2 < 17.11 with 90% reliability. Using the extensive UV through mid-IR broadband photometry available in this field, we study the spectral energy distributions of WISE AGN candidates. We find that, as expected, the WISE AGN selection can identify highly obscured AGNs, but that it is biased toward objects where the AGN dominates the bolometric luminosity output. We study the distribution of reddening in the AGN sample and discuss a formalism to account for sample incompleteness based on the step-wise maximum-likelihood method of Efstathiou et al. The resulting dust obscuration distributions depend strongly on AGN luminosity, consistent with the trend expected for a receding torus. At LAGN ∼ 3 × 1044 erg s−1, 29% ± 7% of AGNs are observed as Type 1, while at ∼4 × 1045 erg s−1 the fraction is 64% ± 13%. The distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Six months of multiwavelength follow-up of the tidal disruption candidate asassn-14li and implied tde rates from asas-sn (2015, background): “However, the galaxy has a mid-IR (MIR) color of (W1−W2) ' 0.01±0.04 in the WISE data, which, along with the non-detection in the X-ray data, provides evidence that any AGN activity is not strong (e.g., Assef et al. 2013).”
Active galactic nuclei: what’s in a name? (2017, background): “…et al. 2004, 2007, 2013; Stern et al. 2005; Hatziminaoglou et al. 2005; Donley et al. 2012), AKARI (Murakami et al. 2007; Oyabu et al. 2011), and the Wide-field Infrared Survey Explorer (WISE: Wright et al. 2010; see, e.g. Stern et al. 2012; Mateos et al. 2012; Wu et al. 2012b; Assef et al. 2013).”
THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION (2015, methodology): “…mechanism for separating quasars and stars and Wide-field Infrared Survey Explorer (WISE ; Wright et al. 2010) data therefore provide additional information for targeting quasars that otherwise resemble stars in optical color space (e.g. Stern et al. 2012; Assef et al. 2013; Yan et al. 2013).”
New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei (2018, background): “Studies in the infrared band indicate that the torus covering factor may be a function of luminosity (e.g., Maiolino et al. 2007, Treister et al. 2008, Assef et al. 2013), and may correlate with other measurable properties (e.g., presence of broad lines in optical spectra; Mateos et al. 2016).”
The dust covering factor in active galactic nuclei (2016, background): “Analysing a large AGN sample from the WISE catalogue, Assef et al. (2013) found that the observed reddening distribution can be explained by a torus-like structure in which thick dust clouds are embedded in a diffuse inter-cloud dust medium.”
ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc (2016, background): “Detections of the host in Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010) data corroborate this picture, as the galaxy has a mid-IR (MIR) color of (W1−W2) ' 0.06± 0.06, implying that any AGN activity in the galaxy is not strong (e.g., Assef et al. 2013).”
The incidence of obscuration in active galactic nuclei (2013, background): “…fraction of absorbed AGN, defined in different and often independent ways, appears to be lower at higher nuclear luminosities (Lawrence & Elvis 1982; Steffen et al. 2003; Ueda et al. 2003; Simpson 2005; Hasinger 2008; Bongiorno et al. 2010; Brusa et al. 2010; Burlon et al. 2011; Assef et al. 2013).”
ASASSN-14ae: a tidal disruption event at 200 Mpc (2014, unknown): “From the WISE W1 and W2 measurements we calculate that the host galaxy has (W1− W2) ' 0.06±0.06 mag, and this blue mid-IR color is further evidence against AGN activity (e.g., Assef et al. 2013).”
Revisiting the Unified Model of Active Galactic Nuclei (2015, background): “There are several examples of SED fitting of luminous, type-I AGNs (Schweitzer et al. 2008; Mor, Netzer & Elitzur 2009; Roseboom et al. 2013; Assef et al. 2013; Lusso et al. 2013).”
GALAXY AND MASS ASSEMBLY (GAMA): MID-INFRARED PROPERTIES AND EMPIRICAL RELATIONS FROM WISE (2014, methodology): “WISE colors have proved to be an excellent AGN selection tool (Jarrett et al. 2011; Stern et al. 2012; Assef et al. 2013), and as a diagnostic for determining the accretion modes amongst radio-loud AGNs (Gurkan et al. 2013).”
The WISE AGN Catalog (2017, background): “…survey of the sky, the majority have been developed for the more recent observatories, such as Spitzer and WISE (Lacy et al. 2004, 2007, 2013; Stern et al. 2005, 2012; Assef et al. 2010, 2013; Jarrett et al. 2011; Donley et al. 2012; Mateos et al. 2012; Messias et al. 2012; Wu et al. 2012).”
IDENTIFICATION OF 1.4 MILLION ACTIVE GALACTIC NUCLEI IN THE MID-INFRARED USING WISE DATA (2015, methodology): “For picking out Spitzer IRAC-selected AGNs down to a limiting magnitude of W2 < 15, the WISE one-color AGN selection criteria of Stern et al. (2012) and Assef et al. (2013) are both very reliable, with 95% and and > 90% reliability, respectively.”
The Sloan Digital Sky Survey Reverberation Mapping Project: Sample Characterization (2018, background): “…Survey Explorer (WISE) survey (Wright et al. 2010), the SDSS-RM sample is more complete in optical color space contaminated by stars (e.g., Schmidt et al. 2010; Morganson et al. 2015) and less biased against dust-reddened type 1 quasars (e.g., Assef et al. 2013) than optical-only color selection.”