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Providing stringent star formation rate limits of z ∼ 2 QSO host galaxies at high angular resolution

Vayner, Andrey and Wright, Shelley A. and Do, Tuan and Larkin, James E. and Armus, Lee and Gallagher, S. C. (2016) Providing stringent star formation rate limits of z ∼ 2 QSO host galaxies at high angular resolution. Astrophysical Journal, 821 (1). Art. No. 64. ISSN 0004-637X.

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We present integral field spectrograph (IFS) with laser guide star adaptive optics (LGS-AO) observations of z ~ 2 quasi-stellar objects (QSOs) designed to resolve extended nebular line emission from the host galaxy. Our data was obtained with W. M. Keck and Gemini North Observatories, using OSIRIS and NIFS coupled with the LGS-AO systems, respectively. We have conducted a pilot survey of five QSOs, three observed with NIFS+AO and two observed with OSIRIS+AO at an average redshift of z = 2.2. We demonstrate that the combination of AO and IFSs provides the necessary spatial and spectral resolutions required to separate QSO emission from its host. We present our technique for generating a point-spread function (PSF) from the broad-line region of the QSO and performing PSF subtraction of the QSO emission to detect the host galaxy emission at a separation of ~0."2 (~1.4 kpc). We detect Hα narrow-line emission for two sources, SDSS J1029+6510 (z_(Hα) = 2.182) and SDSS J0925+0655 (z_(Hα) = 2.197), that have evidence for both star formation and extended narrow-line emission. Assuming that the majority of narrow-line Hα emission is from star formation, we infer a star formation rate (SFR) for SDSS J1029+6510 of 78.4 M_⊙ yr^(−1) originating from a compact region that is kinematically offset by 290–350 km s^(−1). For SDSS J0925+0655 we infer a SFR of 29 M_⊙ yr^(−1) distributed over three clumps that are spatially offset by ~7 kpc. The null detections on three of the QSOs are used to infer surface brightness limits and we find that at 1.4 kpc from the QSO the un-reddened star formation limit is ≾ 0.3 M_⊙ yr^(−1) kpc^(−2). If we assume typical extinction values for z = 2 type-1 QSOs, the dereddened SFR for our null detections would be ≾ 0.6 M_⊙ yr^(−1) kpc^(−2). These IFS observations indicate that while the central black hole is accreting mass at 10%–40% of the Eddington rate, if star formation is present in the host (1.4–20 kpc) it would have to occur diffusely with significant extinction and not in compact, clumpy regions.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Vayner, Andrey0000-0002-0710-3729
Wright, Shelley A.0000-0003-1034-8054
Do, Tuan0000-0001-9554-6062
Larkin, James E.0000-0001-7687-3965
Armus, Lee0000-0003-3498-2973
Additional Information:© 2016 The American Astronomical Society. Received 2014 October 10; accepted 2016 February 22; published 2016 April 11. This work is based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologiae Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). The authors would like to give our thanks to Eric Steinbring, who served as our Gemini phase II liaison for planning this program (GN-2012B-Q-53). Data was also obtained at W.M. Keck Observatory, which was made possible by generous financial support from the W.M. Keck Foundation. The authors would like to acknowledge the dedicated members of the Keck Observatory staff, particularly Jim Lyke and Randy Campbell, who helped with the success of our observations. The authors wish to recognize the significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this "heiau" mountain. S.C.G. thanks the Natural Science and Engineering Research Council of Canada for support. The authors would like to thank the anonymous referee for their extremely detailed comments that greatly improved the overall quality of the article.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:galaxies: high-redshift; galaxies: star formation; methods: observational; quasars: general; quasars: supermassive black holes; techniques: high angular resolution
Issue or Number:1
Record Number:CaltechAUTHORS:20160509-134030443
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Official Citation:Andrey Vayner et al 2016 ApJ 821 64
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66778
Deposited By: Ruth Sustaita
Deposited On:09 May 2016 21:08
Last Modified:02 Nov 2019 16:42

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