Discovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields
Dale Mudd, Paul Martini, Suk Sien Tie, Chris Lidman, Richard McMahon, Manda Banerji, Tamara Davis, Bradley Peterson, Rob Sharp, Michael Childress, Geraint Lewis, Brad Tucker, Fang Yuan, Tim Abbot, Filipe Abdalla, Sahar Allam, Aurelien Benoit-Levy, Emmanuel Bertin, David Brooks, A. Camero Rosell, Matias Carrasco Kind, Jorge Carretero, Luiz N. da Costa, Shantanu Desai, Thomas Diehl, Tim Eifler, David Finley, Brenna Flaugher, Karl Glazebrook, Daniel Gruen, Robert Gruendl, Gaston Gutierrez, Samuel Hinton, Klaus Honscheid, David James, Kyler Kuehn, Nikolav Kuropatkin, Edward Macaulay, M.A.G. Maia, Ramon Miquel, Ricardo Ogando, Andres Plazas, Kevin Riel, Eusebio Sanchez, Basillio Santiago, Michael Schubnell, Ignacio Sevilla-Noarbe, R.C. Smith, Marcelle Soares-Santos, Flavia Sobreira, Eric Suchyta, Molly Swanson, Gregory Tarle, Daniel Thomas, Syed Uddin, Alistair Walker, Bonnie Zhang, DES Collaboration
aa r X i v : . [ a s t r o - ph . GA ] J un Discovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields Discovery of a z=0.65 Post-Starburst BAL Quasar in the DESSupernova Fields
Dale Mudd , Paul Martini , , Suk Sien Tie , , Chris Lidman , Richard McMahon , ,Manda Banerji , , Tamara Davis , Bradley Peterson , , Rob Sharp , , MichaelChildress , , Geraint Lewis , Brad Tucker , , Fang Yuan , , Tim Abbot , FilipeAbdalla , , Sahar Allam , Aur´elien Benoit-L´evy , , , Emmanuel Bertin , , DavidBrooks , A. Camero Rosell , , Matias Carrasco Kind , , Jorge Carretero , , LuizN. da Costa , , Shantanu Desai , , Thomas Diehl , Tim Eifler , , David Finley ,Brenna Flaugher , Karl Glazebrook , Daniel Gruen , , Robert Gruendl , , Gas-ton Gutierrez , Samuel Hinton , Klaus Honscheid , , David James , Kyler Kuehn ,Nikolav Kuropatkin , Edward Macaulay , M. A. G. Maia , , Ramon Miquel , ,Ricardo Ogando , , Andres Plazas , Kevin Riel , Eusebio Sanchez , BasillioSantiago , , Michael Schubnell , Ignacio Sevilla-Noarbe , R. C. Smith , MarcelleSoares-Santos , Flavia Sobreira , , Eric Suchyta , Molly Swanson , Gregory Tarle ,Daniel Thomas , Syed Uddin , Alistair Walker , Bonnie Zhang , The DES Collabo-ration Department of Astronomy, The Ohio State University, Columbus, Ohio 43210, USA Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 Australian Astronomical Observatory, 105 Delhi Rd, North Ryde NSW 2113, Australia Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK School of Mathematics and Physics, University of Queensland, QLD 4072, Australia CAASTRO: ARC Centre of Excellence for All-sky Astrophysics Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd., Weston ACT 2611, Australia Department of Physics and Astronomy, Curtin University, Kent Street, Bentley, Perth, Western Australia, 6102 School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, UK Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, the Australian National University, Cotter Rd., Canberra ACT 2611, Australia Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney, NSW 2006, Australia Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena, Chile Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510, USA CNRS, UMR 7095, Institut d’Astrophysique de Paris, F-75014, Paris, France Sorbonne Universit´es, UPMC Univ Paris 06, UMR 7095, Institut d’Astrophysique de Paris, F-75014, Paris, France Laborat´orio Interinstitucional de e-Astronomia - LIneA, Rua Gal. Jos´e Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil Observat´orio Nacional, Rua Gal. Jos´e Cristino 77, Rio de Janeiro, RJ - 20921-400, Brazil Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA National Center for Supercomputing Applications, 1205 West Clark St., Urbana, IL 61801, USA Institut de Ci`encies de l’Espai, IEEC-CSIC, Campus UAB, Carrer de Can Magrans, s/n, 08193 Bellaterra, Barcelona, Spain Institut de F´ısica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193 Bellaterra (Barcelona) Spain Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany Faculty of Physics, Ludwig-Maximilians-Universit¨at, Scheinerstr. 1, 81679 Munich, Germany Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA Centre for Astrophysics & Supercomputing, Swinburne University of Technology, Victoria 3122, Australia Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA Department of Physics, The Ohio State University, Columbus, OH 43210, USA Instituci´o Catalana de Recerca i Estudis Avanc¸ats, E-08010 Barcelona, Spain Centro de Investigaciones Energ´eticas, Medioambientales y Tecnol´ogicas (CIEMAT), Madrid, Spain Instituto de F´ısica, UFRGS, Caixa Postal 15051, Porto Alegre, RS - 91501-970, Brazil Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA ICTP South American Institute for Fundamental Research Instituto de F´ısica Te´orica, Universidade Estadual Paulista, S˜ao Paulo, Brazil on. Not. R. Astron. Soc. , 000–000 (0000) Printed 13 June 2016 (MN L A TEX style file v2.2)
ABSTRACT
We present the discovery of a z=0.65 low-ionization broad absorption line (LoBAL) quasarin a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy fromthe Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, andrarer still is that this object also exhibits broad FeII (an FeLoBAL) and Balmer absorption.This is the first BAL quasar that has signatures of recently truncated star formation, whichwe estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL requirehigh column densities, which could be explained by the emergence of a young quasar froman early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of thestarburst component is comparable to estimates of the lifetime of quasars, so if we assume thequasar activity is related to the truncation of the star formation, this object is better explainedby the blast wave scenario.
Key words: galaxies: active – galaxies: starburst – quasars: absorption lines
Correlations of the mass of the central supermassive black hole(SMBH) with host galaxy properties such as velocity dispersion(Gebhardt et al. 2000; Ferrarese & Merritt 2000) suggest that aSMBH’s growth is linked to the evolution of the host galaxythrough some feedback process (e.g. Heckman & Best 2014).The most pronounced phase of SMBH growth is the quasarphase, where most of the spectral energy distribution can be ex-plained by a thin accretion disk of material around the SMBH(Shakura & Sunyaev 1973; Koratkar & Blaes 1999), a hot corona,and a broad line region on larger scales (e.g. Peterson 1997). Onemethod of triggering quasar activity is a merger that involves atleast one gas-rich galaxy (Sanders et al. 1988; Silk & Rees 1998;Komossa et al. 2003; Di Matteo et al. 2005; Piconcelli et al. 2010).During gas-rich mergers, gas funnels towards the central regionsof the galaxies and some fraction accretes onto the central SMBH.This substantial influx of gas and dust may often obscure the earlyphases of quasar activity.Gas-rich mergers also produce a large increase in star forma-tion, up to 100-1000 times the galaxy’s quiescent rate. These ratescan quickly exhaust the gas supply, and eventually the star forma-tion rate must return to a lower value. It is unclear if this is primarilycaused by the expulsion of star-forming gas due to the quasar, feed-back from the star formation process, or consumption of the gas bystar formation and the SMBH. If the increased star formation ratedecreases quickly compared to the total star formation history, thegalaxy goes through a post-starburst phase, which is characterizedby the strong absorption lines prevalent in A type stars combinedwith a K type spectrum from an older population (Dressler & Gunn1983; Zabludoff et al. 1996). The absence of stellar features dueto shorter-lived O and B type stars would indicate star formationceased tens to hundreds of Myr ago. Some post-starburst galax-ies also exhibit blueshifted absorption from winds (Tremonti et al.2007; Coil et al. 2011), and at least some wind-driven outflowsfrom starbursts appear to be delayed by 10 Myr or more afterthe star formation burst (Sharp & Bland-Hawthorn 2010; Ho et al.2016).A significant fraction of all post-starburst galaxies hostquasars (Brotherton et al. 1999, 2002; Cales et al. 2013) or someform of lower luminosity active galactic nuclei (AGN). Goto (2006)found that 0.2% of all galaxies are in a post-starburst state, com-pared to 4.2% of quasars having these post-starburst features.Quasars hosted by post-starburst galaxies typically had intense starformation that ended − years ago. Cales et al. (2013) found that older post-starburst quasars in elliptical galaxies tend to havesigns of a recent merger, which suggests that a major merger eventfueled both the previous star formation and current quasar activ-ity. Tremonti et al. (2007) and others argue that the presence ofblueshifted absorption of a few hundred to a few thousand km s − in some post-starburst quasars is evidence that these objects had alarge, galaxy-scale wind ∼ years ago, although the energy inthese winds may not be enough to have quenched star formation(Coil et al. 2011). Similar winds are seen in ongoing starbursts, butthese tend to be a factor of a few weaker than in post-starbursts ofcomparable luminosity (Tremonti et al. 2007).When the winds from a quasar are especially prominent,they are classified as broad absorption line (BAL) quasars. BALsare characterized by prominent, blueshifted absorption lines of2000 km s − or more (Weymann et al. 1991). BALs are presentin 20-40% of all quasars, depending on the selection method(Trump et al. 2006; Dai et al. 2008; Urrutia et al. 2009). The ma-jority of BALs only exhibit absorption in high ionization states,such as CIV, and are referred to as HiBALs. BALs with absorptionin lower ionization lines, such as MgII, are referred to as LoBALs.A small subset of LoBALs also have FeII and/or FeIII absorptionand are known as FeLoBALs (Hazard et al. 1987). Rarest of all arethe handful of objects with absorption in the Balmer lines (Hall2007; Zhang et al. 2015). Using SDSS data, Trump et al. (2006)find that HiBALs, LoBALs, and FeLoBALs constitute 26%, 1.3%,and 0.3%, respectively, of their sample of over 16,000 quasars. Incontrast, Dai et al. (2008) and Urrutia et al. (2009) find BALs aremuch more common. When selected with both SDSS and 2MASSto alleviate the bias from reddening, they report 37%, 32%, and32% of quasars are HiBALs, LoBALs, and FeLoBALs, respec-tively. This selection method identifies all LoBALs as FeLoBALs.FeLoBALs are the most heavily reddened BAL subtype,and the iron features necessitate high column densities (e.g.Korista et al. 2008). They can have broad iron emission and ab-sorption from FeIII in addition to FeII, and, in very rare cases, onlyFeIII (Hall et al. 2002). The absorption troughs are also observedto vary between objects from several distinct, narrow troughs, toblanketing most of the emission from the quasar shortward of theMgII doublet. Both LoBALs and FeLoBALs also tend to be X-rayfaint, further implying that there is a large column density that pre-vents a direct view of the central source (e.g. Mathur et al. 1995;Green et al. 2001).There remains much debate about the exact nature of FeLoB-ALs. With their considerable reddening and high inferred column iscovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields densities, some argue that they are transitional quasars, movingfrom a dust-enshrouded star formation phase to an unobscuredquasar phase (Voit et al. 1993; Egami et al. 1996; Farrah et al.2007, 2010). The highly absorbed FeLoBALs are also more likelyto be radio sources, and may be transition objects between radioloud and radio quiet quasars (Becker et al. 1997). Alternatively,Faucher-Gigu`ere et al. (2012) propose that the absorption is fromhigh density clouds along the line of sight that have been disruptedby a blast wave from the SMBH, rather than a wind pushing outa dusty cocoon. This would create the absorbers in-situ, allowingthem to be either close to the central AGN or farther out in thegalaxy but along our line of sight. The young, dust-enshrouded sce-nario is less flexible, as the absorbers should be within the centralfew parsecs.We have discovered an FeLoBAL quasar with Balmer absorp-tion and a post-starburst spectrum that was selected using dataobtained by the the Dark Energy Survey (DES; Flaugher 2005;Flaugher et al. 2015) and the OzDES collaboration (Yuan et al.2015). The quasar was found in one of the 10 “supernova fields”(3 deg each, Kessler et al. 2015) that are monitored to discoverType Ia supernovae. OzDES obtains approximately monthly spec-tra of the 10 supernova fields with the AAOmega spectrograph(Smith et al. 2004; Sharp et al. 2006) on the 4m Anglo-AustralianTelescope (AAT). Two of its main science goals are measuring red-shifts for thousands of host galaxies of Type Ia supernovae dis-covered with DES photometry and repeatedly observing hundredsof quasars as part of a large-scale reverberation mapping project(King et al. 2015). OzDES also obtains spectra of various otherclasses of objects, including luminous red galaxies, BAL quasars,and white dwarfs.Several of the targets for the DES/OzDES reverberation map-ping project are BAL quasars that were selected to monitor theirlong-term absorption and emission line variability. Upon stack-ing several spectra, we discovered that one of these objects, DESQSO J033049.33-283249.7 (hereafter DES QSO J0330-28), re-sides in a post-starburst galaxy. This appears to be the first knownBAL quasar in a post-starburst galaxy. We also note that this isa FeLoBAL with Balmer absorption, making it rare even amongBALs, and that it was first chosen as a target candidate from a com-bination of optical and infrared color cuts described in Banerji et al.(2015), Equation 6. In Section 2, we describe the DES and OzDESobservations and accumulate other values from the literature on thisunique object. In Section 3, we characterize both the outflow andmodel the properties of the host galaxy stellar population using thestacked OzDES spectra. We summarize and present our conclusionin Section 4. All of the spectra of DES QSO J0330-28 were obtained withthe AAT 4m at Siding Spring Observatory as part of the OzDESproject. The double beam fiber-fed spectrograph uses the 580Vgrating and 385R gratings leading to dispersions of 1 ˚A/pixel and1.6 ˚A/pixel in the blue and red arms, respectively, with the dichroicsplit at 5700 ˚A. The resolution of the spectrograph is R ∼ ,and the wavelength range spans 3700-8800 ˚A.We present the stacked spectrum in Figure 1 in both the ob-served and rest frame. This is a combination of four spectra taken Australian Dark Energy Survey; alternatively, Optical redshifts for DES
Figure 1.
Stacked spectrum of DES QSO J0330-28 at z = 0.65. The LoBALfeatures are prominent at wavelengths shorter than the MgII line at rest-frame 2798 ˚A. The absorption features around rest-frame 3900 ˚A are fromhost galaxy stars.
Table 1.
DES QSO J0330-28 PhotometryBand Name Cent. Wave Magnitude (Error) g r i z Y µ m 19.00 (0.02) J µ m 18.89 (0.04) H µ m 18.77 (0.05) K µ m 18.45 (0.05) W1 µ m 17.64 (0.03) W2 µ m 17.01 (0.03) W3 µ m 15.92 (0.06) W4 µ m 15.01 (0.22)ATLAS 1.474 GHz a (20) Photometry for DES QSO J0330-28 taken from DES for grizY , VHS for
JHK (McMahon et al. 2013), and WISE for W1-W4 (Wright et al. 2010).The DES data are PSF magnitudes obtained from the coadd of the first yearof observations. All magnitudes are given in the AB system aside from theradio data from ATLAS (Franzen et al. 2015; Mao et al. 2012). a This is in µ janksy rather than magnitudes. over the course of two years and the combined exposure time is160 minutes. We derived the host galaxy redshift of z = 0.65 basedon the higher order Balmer lines around rest-wavelength 4000 ˚A.There is also a prominent Balmer break shortward of the absorp-tion. These are the signs of a post-starburst galaxy with recentlyquenched star formation. At shorter wavelengths, there is a sharpdrop in flux at the rest wavelength of the MgII 2798 ˚A emissionline. This corresponds to blueshifted absorption out to 5000 kms − from the systemic redshift. Other absorption troughs in the rest-frame UV correspond to metastable states of Fe II, particularly at2750 ˚A, 2880 ˚A, and 2985 ˚A. There may be MgI 2853 ˚A, but this fallsin an FeII absorption trough. The most common FeIII features areblueward of our spectral coverage.We provide photometry for this object in Table 1. Thisincorporates grizY from DES, JHK from the VHS survey(McMahon et al. 2013), and W1 , W2 , W3 , W4 from WISE (Wright et al. 2010). The DES and WISE magnitudes are calcu-
Mudd et al.
Figure 2.
DES images of DES QSO J0330-28 in g (top left) , r (top right) , i (bottom left) , and K (bottom right). Eachbox is ′′ on a side centered on the quasar. The g , r , and i images arefrom DES, and the K band image is from the VISTA VIDEO (Jarvis et al.2013) survey. The three crosses in the r image correspond to three sourcesthat have photometric redshifts consistent with DES QSO J0330-28, whichsuggests a merger. lated using PSF fits, whereas the VHS data use a ′′ aperture. Allmagnitudes have been transformed to the AB system. Both the veryred colors (e.g. r − K = 0.86 AB) and spectral shape indicatevery substantial reddening, which is quite common with FeLoB-ALs (Sprayberry & Foltz 1992; Hall et al. 1997). The DES g, r, i and VISTA K images are shown in Figure 2. These images showseveral small objects in the immediate vicinity of the quasar thatsuggest an interacting or merging system, and three of the objectshave photometric redshifts consistent with DES QSO J0330-28.This quasar was also detected as a radio source in the ATLAS sur-vey (Franzen et al. 2015; Mao et al. 2012) at 1.474 GHz. If we ex-trapolate the ATLAS measurement to 5 GHz with a α = 0 . , theratio of rest frame 5 GHz flux density to that at 4400 ˚ A is abouttwo. This quasar is consequently radio quiet/intermediate under thedefinition that a ratio less than one is quiet and greater than ten isradio loud. The result is consistent with the idea that LoBALs maybe quasars moving between a radio loud and radio quiet phase andsome work suggests that the LoBAL fraction in quasars decreasesas a function of radio luminosity (Dai et al. 2012). This object is notdetected in archival Chandra data, consistent with previous stud-ies that have found FeLoBALs are X-ray faint (Mathur et al. 1995;Green et al. 2001).
We fit the stacked spectrum with STARLIGHT(Cid Fernandes et al. 2004, 2005a,b) over the wavelength span notdominated by the FeLoBAL’s broad absorption and emission lines(see Figure 3). This corresponds to approximately 3300-4800 ˚A inthe rest frame. We do not fit to longer wavelengths in order to avoid
Figure 3.
The best fit single metallicity model with Z = 0.02 Z ⊙ . The data(black) are fit by a model (magenta) that combines a quasar template (cyan)and three major stellar components: 44% of the light comes from a younger,recently quenched population with an age of 40 Myr (dark blue), and 24%comes from older populations of 10 and 13 Gyr (green and red, respec-tively). The remainder of the light comes from the quasar. The masked re-gions are left out of the fit due to possible broad quasar emission from H β and broad absorption in the wings of higher order Balmer lines from thequasar. H β contamination. To account for the quasar component, we cre-ated a quasar template from stacked spectra of 10 quasars from thereverberation mapping sample that are most similar in redshift andluminosity to DES QSO J0330-28. We initially ran STARLIGHTover a grid of models supplied by Bruzual & Charlot (2003) thatspan ages of 1 Myr to 13 Gyr and metallicites from 0.005-2.5 Z ⊙ .The best fit model has approximately 45% of the light from twoyoung stellar populations of 40 and 55 Myr, 40% from our quasartemplate, and the remainder from an older population of 6-7Gyr. The metallicity for the varied components is consistent withsubsolar to solar. This fit has χ red = 0.85. We also performed fitsat single metallicities and found in most instances that between30-50% of the light is from 40 and 55 Myr populations and20-50% is from the quasar. These fits had χ red ranging from 0.9-1.2and show the relative insensitivity of the population ages to themetallicity. The strength of the higher order Balmer lines depthsdo not match perfectly with any age/metallicity combination. Thisis likely because of the impact of Balmer absorption in the BAL,and perhaps also some mismatch with the quasar template and thisquasar. For each grid of models, we also fit for the best globalextinction and best extinction for each component. We found thebest fit A V was 0-0.04 in most cases. However, there is a classof single-metallicity models around solar where the best fit has ayounger population (5 Myr) with some extinction ( A V = 0.37) asthe dominant stellar component. There are a number of absorption troughs present at shorter wave-lengths than the stellar absorption features in addition to broad ab-sorption associated with some of the Balmer lines. BAL features aretypically described by their balnicity index. This metric originatedin Weymann et al. (1991) for HiBALs and the CIV line. By theirdefinition, a quasar was considered a BAL if it had a balnicity in-dex
BI > . Later, Hall et al. (2002) proposed the absorptive index(AI) as an alternative identifier, which is more sensitive to troughsat lower velocities and likewise identifies BALs with AI > . Both iscovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields BI and AI are integrals over velocity on the blue side of an emis-sion line. The BI requires the trough to extend at least 3000km s − and drop by at least 10% of the normalized conitnuum flux. TheAI, however, begins the integral at 0km s − and is more sensitiveto lower velocity and weaker troughs.It is difficult to measure these values in FeLoBALs like DESQSO J0330-28 because these objects have such heavy reddeningand the widespread iron absorption/emission makes the continuumpoorly defined. The STARLIGHT fit, partially because it couldonly fit a narrow wavelength range due to the BAL features, has abest fit A V of 0.04. However, DES QSO J0330-28 is clearly highlyreddened at shorter wavelengths (see Figure 1). To correct for this,we applied various values of A V to our quasar template for an SMCextinction curve (Gordon et al. 2003) until we found the best fit tothe red half of the MgII emission line at 2798 ˚A. While no singlevalue gives a satisfactory fit to either the extinction or the contin-uum, the spectral slope is broadly consistent with A V = 1 − . mag. This is small given how X-ray faint (Green et al. 2001) andred many LoBALs are, but is also poorly constrained by the avail-able data. A likely cause for the difficulty is that there may be par-tial obscuration; that is, varying amounts of extinction to differentregions of the galaxy and quasar emission region. Without a goodcontinuum fit, we cannot reliably measure AI or BI for this ob-ject. Nevertheless, the velocity spread of the absorption troughs isreasonably clear. Figure 4 shows that the MgII absorption spansapproximately 5000 km s − before a small rise that is likely dueto FeII emission at 2750 ˚A, which then has its own blueshifted ab-sorption. The depth and width of the trough means that this objectwould likely meet the conditions for both AI and BI ¿ 0 for MgII.We next compare the velocity extent of the MgII componentto other absorption troughs, namely FeII at 2750 ˚A, 2880 ˚A, and2985 ˚A, and H β . Figure 4 shows in both cases the data are consistentwith a similar range of blueshifted absorption, and this suggests acommon origin.BALs have a large diversity of spectral morphologies, andDES QSO J0330-28 is most similar to SDSS J112526.13+002901.3(Hall et al. 2002) with regard to the approximate shape and strengthof the emission and absorption features. That SDSS quasar haszero balnicity index, but an absorptive index of almost 500km s − .While we cannot cleanly measure the continuum of DES QSOJ0330-28, it should also have a nonzero absorptive index. Hall et al.(2002) also classified SDSS J112526.13+002901.3 as a many nar-row troughs FeLoBAL with HeI absorption. We do not see evidencefor either of these characteristics in DES QSO J0330-28. SDSSJ112526.13+002901.3 also does not have the same post-starburstfeatures that make DES QSO J0330-28 unique.We perform a similar analysis to Hall (2007) for our H β absorption to determine a lower limit column density N Hβ =5 . × cm − . This value is about a factor of 100 smaller thanthe column density measurement for the Hall (2007) FeLoBAL,but likely underestimated for DES QSO J0330-28 due to the strongunabsorbed galaxy emission at these wavelengths. The current picture for quasar evolution in the merger scenario be-gins with the collision of a dust- and gas-rich galaxy with anothersystem. Dynamical processes drive material towards the galaxies’centers and fuels star formation and accretion onto the SMBH. Thequasar is initially obscured by the dust, but eventually the materialdisperses and the quasar becomes easily visible. FeLoBALs have
Figure 4.
Highlight of the BAL troughs. In each inset, the arrows cor-respond to the systemic redshift and the horizontal bars correspond to ablueshift velocity of 5000 km s − . This fits well for MgII and FeII, andthere is also Balmer absorption that is consistent with this outflow velocity.The dotted line is the best fit model for the quasar and stellar components.The model fits well around the Balmer lines, but vastly overestimates theflux at shorter wavelengths. attracted particular interest because the very high column densityabsorption is indicative of a substantial outflow, perhaps associatedwith this transition from obscured to unobscured. A second sce-nario proposed by Faucher-Gigu`ere et al. (2012) is that a blast waveis launched from the quasar that impacts a high density cloud alongthe line of sight. This would also create the observed column den-sities, reddening, and absorption troughs seen in FeLoBALs. Onedistinction between these scenarios is in where the absorbing mate-rial lies. For the transition objects, the absorbing material would bearound the quasar and in the process of being blown away, whereasfor the blast wave model it is possible to impact a cloud on muchlarger scales than the central few parsecs.Variability is one way to test the location of the absorbers.The constraints from several variable FeLoBALs (e.g., Hall et al.2011; McGraw et al. 2015; Vivek et al. 2012) place the absorbingmaterial on the order of a few to tens of parsecs from the centralsource. This assumes a cloud-crossing model where the changesarise from an absorber moving across the line of sight. In contrast,other studies suggest the absorption is on kpc scales (Moe et al.2009; Bautista et al. 2010; Dunn et al. 2010). Moe et al. (2009) de-rived a distance to one outflow of ∼ Mudd et al. absorbed and the stellar component less so if there is a low coveringfraction of the galaxy-wide absorbers.If we assume the quasar and starburst triggered simultane-ously, we can use the starburst age to evaluate which modelFeLoBAL scenario is more probable. Star formation was truncatedor quenched in DES QSO J0330-28 around 50 Myr ago in most ofour models. This time is comparable to estimates for quasar life-times of around − years (e.g., Yu & Tremaine 2002; Martini2004) and implies that this FeLoBAL did not turn on recently,which is in conflict with the young quasar scenario. The FeLoBALfeatures cannot be due to the same feedback processes that abruptlyended the star formation ∼
50 Myr ago, as they would havedispersed due to Kelvin-Helmholtz or Rayleigh-Taylor instabili-ties. These features are consistent with the Faucher-Gigu`ere et al.(2012) model in which the absorption is produced by clouds of ma-terial that have been compressed by a radiative blast wave. Thekey aspect of the blast wave model for DES QSO J0330-28 is thatthe blast wave is not tied to a particular evolutionary phase of thequasar.We plan to obtain future, higher signal-to-noise ratio spectraover a broader wavelength range to derive better stellar populationand reddening parameters. We will also obtain new spectral epochsas the OzDES program progresses, and we will use these data tosearch for BAL variability to attempt to measure the distance of theabsorber from the central source.
DM would like to gratefully acknowledge the helpful comments bySmita Mathur on a draft of this manuscript.Funding for the DES Projects has been provided by theU.S. Department of Energy, the U.S. National Science Founda-tion, the Ministry of Science and Education of Spain, the Sci-ence and Technology Facilities Council of the United Kingdom, theHigher Education Funding Council for England, the National Cen-ter for Supercomputing Applications at the University of Illinois atUrbana-Champaign, the Kavli Institute of Cosmological Physics atthe University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institutefor Fundamental Physics and Astronomy at Texas A&M Univer-sity, Financiadora de Estudos e Projetos, Fundac¸ ˜ao Carlos ChagasFilho de Amparo `a Pesquisa do Estado do Rio de Janeiro, Con-selho Nacional de Desenvolvimento Cient´ıfico e Tecnol´ogico andthe Minist´erio da Ciˆencia, Tecnologia e Inovac¸ ˜ao, the DeutscheForschungsgemeinschaft and the Collaborating Institutions in theDark Energy Survey.The Collaborating Institutions are Argonne National Labora-tory, the University of California at Santa Cruz, the University ofCambridge, Centro de Investigaciones Energ´eticas, Medioambien-tales y Tecnol´ogicas-Madrid, the University of Chicago, Univer-sity College London, the DES-Brazil Consortium, the Universityof Edinburgh, the Eidgen¨ossische Technische Hochschule (ETH)Z¨urich, Fermi National Accelerator Laboratory, the University ofIllinois at Urbana-Champaign, the Institut de Ci`encies de l’Espai(IEEC/CSIC), the Institut de F´ısica d’Altes Energies, LawrenceBerkeley National Laboratory, the Ludwig-Maximilians Univer-sit¨at M¨unchen and the associated Excellence Cluster Universe, theUniversity of Michigan, the National Optical Astronomy Observa-tory, the University of Nottingham, The Ohio State University, theUniversity of Pennsylvania, the University of Portsmouth, SLACNational Accelerator Laboratory, Stanford University, the Univer- sity of Sussex, Texas A&M University, and the OzDES Member-ship Consortium.The DES data management system is supported by the Na-tional Science Foundation under Grant Number AST-1138766.The DES participants from Spanish institutions are partially sup-ported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986, and Centro de Excelencia Severo OchoaSEV-2012-0234. Research leading to these results has receivedfunding from the European Research Council under the EuropeanUnion’s Seventh Framework Programme (FP7/2007-2013) includ-ing ERC grant agreements 240672, 291329, and 306478.The data in this paper were based on observations obtained atthe Australian Astronomical Observatory.Part of this research was conducted by the Australian ResearchCouncil Centre of Excellence for All-sky Astrophysics (CAAS-TRO), through project number CE110001020.
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