Hunting for Monsters Selecting and Characterizing Obscured Quasars with WISE Kevin Hainline Hidden Monsters Dartmouth College August 2016
Ryan Hickox Dartmouth College Mike DiPompeo Christopher Carroll Raphael Hviding Vivyan Yan Adam Myers University of Wyoming Laura Trouille Northwestern University
Given the importance in selecting large samples of obscured active galactic nuclei Clustering Analysis Mainieri et al. (2014) Host Galaxy Properties dipompeo et al. (2014) see: Ross et al. (2009), Hickox et al. (2011) Cosmic X-ray Background see: Kocevski et al. (2012); Santini et al. (2012), Hainline et al. (2012) AGN Triggering Mechanisms Heavily Obscured Sources Ueda et al. (2003) see: Woltjer (1989); Comastri et al. (1995) image credit: HST 6 see: Hopkins et al. (2006); Somerville et al. (2008) Villforth et al. (2014)
The question becomes: What is the best way to select obscured quasars? (well, that s a question with too much baggage) How about we just go with, instead: Can we select large samples of obscured quasars purely photometrically, using publicly available data sets?
One of the largest samples of obscured quasars comes from SDSS: Reyes et al. (2008) Yuan et al. (2016) see also Kauffmann et al. (2003), Hao et al. (2005a), Zakamska et al. (2003), and Mullaney et al. (2013) for samples of obscured quasars at z < 1, and Alexandroff et al. (2013) and Ross et al. (2015) for samples of obscured obscured quasars at z > 2.
But can we find these objects without having to take a spectrum of each one individually?
Observations in the infrared have been used to target obscured AGNs which have strong infrared power laws from warm and hot dust heated by accretion onto the supermassive black hole. Lacy et al. (2013) Assef et al. (2015) A large population of obscured quasars were found using purely Spitzer selection Hot-DOGs, see Eisenhardt et al. (2012), Wu et al. (2012)
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) Stern et al. (2012)
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) Jarrett et al. (2011)
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) Mateos et al. (2012
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
An aside. What s going on here?
Let s create some toy SED models Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) elliptical template AGN template total SED increasing dust obscuration
Assef et al. (2010) elliptical template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
Assef et al. (2010) star-forming template AGN template total SED
What happens to the WISE color of an elliptical or star-forming galaxy as you increase the bolometric luminosity of an AGN, and change the level of nuclear obscuration?
SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
z < 0.1 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) elliptical template star-forming template
z = 0.1-0.3 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
z = 0.3-0.5 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
z = 0.5-0.7 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
z = 0.7-0.9 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016)
So, infrared selection techniques won t select for all of the obscured quasars, but can we find obscured quasars purely photometrically?
To test this, we selected objects in two groups, primarily separated by their [W4] photometry and optical to infrared colors Hickox et al. (2007) Hainline et al. (2014b)
We used the Robert Stobie Spectrograph on the Southern African Large Telescope (SALT) to obtain optical spectra of our sample
Optical Spectroscopy from SALT shows a broad range of optical spectroscopic properties
Optical Spectroscopy from SALT shows a broad range of optical spectroscopic properties
Our sample also includes interesting high-z quasars Hainline et al. (2014) Broad-Absorption Lines Double-peaked Lyman-α emission
The majority of the spec-z s indicate that the objects extend out to z < 0.8, with IR luminosities similar to SDSS quasars Hainline et al. (2014b)
Optical line ratios are strongly indicative of AGN activity: The TBT diagram AGNs Rest-frame g-z color Star-forming galaxies Hainline et al. (2014)
But can we explore those objects with the highest levels of obscuration? z = 0.3-0.5 SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) luminous obscured quasars Eisenhardt et al. (2012)
NuSTAR followup of some of the more obscured sources yielded three non-detections and one marginal detection Yan et al. in prep. (SEE POSTER 15, SESSION 1)
Hviding et al. in prep (SEE POSTER 3, SESSION 1) SDSS-selected Obscured Quasars Reyes et al. (2008) Yuan et al. (2016) These objects were selected to have significant W4 detections, which would be expected if their infrared power-law extended to longer wavelengths.
Hviding et al. in prep
Hviding et al. in prep
Conclusions - WISE selection criteria are trained to find AGNs that are luminous compared to their host galaxies, with only minimal amounts of extinction. - However, by using optical and infrared photometry together, obscured sources can be uncovered (Hainline et al. 2014) - The most obscured sources found through SDSS+WISE selection would not be found even in with NuSTAR! (Yan et al. in prep) - A follow-up campaign is being done to target regions of WISE color space spanned by heavily obscured quasars at z < 1.0 (Hviding et al. in prep).