Extremely red quasars in BOSS

F. Hamann, N.~L. Zakamska, N. Ross, I. Paris, R.~M. Alexandroff, C. Villforth, G.~T. Richards, H. Herbst, W.~N. Brandt, B. Cook, K.~D. Denney, J.~E. Greene, D.~P. Schneider, M.~A. Strauss

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Abstract

Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual ‘wingless’ line profiles, large N v/Lyα, N v/C iv, Si iv/C iv and other flux ratios, and very broad and blueshifted [O iii] λ5007. Here we present a new catalogue of C iv and N v emission-line data for 216 188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR colour, secondarily on REW(C iv), and not at all on luminosity or the Baldwin Effect. We identify a ‘core’ sample of 97 ERQs with nearly uniform peculiar properties selected via i–W3 ≥ 4.6 (AB) and REW(C iv) ≥ 100 Å at redshifts 2.0–3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity 〈log L(ergs s−1)〉 ∼ 47.1, sky density 0.010 deg−2, surprisingly flat/blue UV spectra given their red UV-to-mid-IR colours, and common outflow signatures including BALs or BAL-like features and large C iv emission-line blueshifts. Their SEDs and line properties are inconsistent with normal quasars behind a dust reddening screen. We argue that the core ERQs are a unique obscured quasar population with extreme physical conditions related to powerful outflows across the line-forming regions. Patchy obscuration by small dusty clouds could produce the observed UV extinctions without substantial UV reddening.
Original languageEnglish
Pages (from-to)3431-3463
Number of pages33
JournalMonthly Notices of the Royal Astronomical Society
Volume464
Issue number3
DOIs
Publication statusPublished - 26 Sep 2016

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quasars
baryons
oscillation
oscillations
outflow
erg
extinction
dust
luminosity
color
occultation
catalogs
sky
signatures
galaxies
profiles
effect
physical conditions
young

Keywords

  • galaxies: active, quasars: absorption lines, quasars: emission lines, quasars: general

Cite this

Hamann, F., Zakamska, N. L., Ross, N., Paris, I., Alexandroff, R. M., Villforth, C., ... Strauss, M. A. (2016). Extremely red quasars in BOSS. Monthly Notices of the Royal Astronomical Society, 464(3), 3431-3463. https://doi.org/10.1093/mnras/stw2387

Extremely red quasars in BOSS. / Hamann, F.; Zakamska, N.~L.; Ross, N.; Paris, I.; Alexandroff, R.~M.; Villforth, C.; Richards, G.~T.; Herbst, H.; Brandt, W.~N.; Cook, B.; Denney, K.~D.; Greene, J.~E.; Schneider, D.~P.; Strauss, M.~A.

In: Monthly Notices of the Royal Astronomical Society, Vol. 464, No. 3, 26.09.2016, p. 3431-3463.

Research output: Contribution to journalArticle

Hamann, F, Zakamska, NL, Ross, N, Paris, I, Alexandroff, RM, Villforth, C, Richards, GT, Herbst, H, Brandt, WN, Cook, B, Denney, KD, Greene, JE, Schneider, DP & Strauss, MA 2016, 'Extremely red quasars in BOSS', Monthly Notices of the Royal Astronomical Society, vol. 464, no. 3, pp. 3431-3463. https://doi.org/10.1093/mnras/stw2387
Hamann F, Zakamska NL, Ross N, Paris I, Alexandroff RM, Villforth C et al. Extremely red quasars in BOSS. Monthly Notices of the Royal Astronomical Society. 2016 Sep 26;464(3):3431-3463. https://doi.org/10.1093/mnras/stw2387
Hamann, F. ; Zakamska, N.~L. ; Ross, N. ; Paris, I. ; Alexandroff, R.~M. ; Villforth, C. ; Richards, G.~T. ; Herbst, H. ; Brandt, W.~N. ; Cook, B. ; Denney, K.~D. ; Greene, J.~E. ; Schneider, D.~P. ; Strauss, M.~A. / Extremely red quasars in BOSS. In: Monthly Notices of the Royal Astronomical Society. 2016 ; Vol. 464, No. 3. pp. 3431-3463.
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AU - Hamann, F.

AU - Zakamska, N.~L.

AU - Ross, N.

AU - Paris, I.

AU - Alexandroff, R.~M.

AU - Villforth, C.

AU - Richards, G.~T.

AU - Herbst, H.

AU - Brandt, W.~N.

AU - Cook, B.

AU - Denney, K.~D.

AU - Greene, J.~E.

AU - Schneider, D.~P.

AU - Strauss, M.~A.

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N2 - Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual ‘wingless’ line profiles, large N v/Lyα, N v/C iv, Si iv/C iv and other flux ratios, and very broad and blueshifted [O iii] λ5007. Here we present a new catalogue of C iv and N v emission-line data for 216 188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR colour, secondarily on REW(C iv), and not at all on luminosity or the Baldwin Effect. We identify a ‘core’ sample of 97 ERQs with nearly uniform peculiar properties selected via i–W3 ≥ 4.6 (AB) and REW(C iv) ≥ 100 Å at redshifts 2.0–3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity 〈log L(ergs s−1)〉 ∼ 47.1, sky density 0.010 deg−2, surprisingly flat/blue UV spectra given their red UV-to-mid-IR colours, and common outflow signatures including BALs or BAL-like features and large C iv emission-line blueshifts. Their SEDs and line properties are inconsistent with normal quasars behind a dust reddening screen. We argue that the core ERQs are a unique obscured quasar population with extreme physical conditions related to powerful outflows across the line-forming regions. Patchy obscuration by small dusty clouds could produce the observed UV extinctions without substantial UV reddening.

AB - Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual ‘wingless’ line profiles, large N v/Lyα, N v/C iv, Si iv/C iv and other flux ratios, and very broad and blueshifted [O iii] λ5007. Here we present a new catalogue of C iv and N v emission-line data for 216 188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR colour, secondarily on REW(C iv), and not at all on luminosity or the Baldwin Effect. We identify a ‘core’ sample of 97 ERQs with nearly uniform peculiar properties selected via i–W3 ≥ 4.6 (AB) and REW(C iv) ≥ 100 Å at redshifts 2.0–3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity 〈log L(ergs s−1)〉 ∼ 47.1, sky density 0.010 deg−2, surprisingly flat/blue UV spectra given their red UV-to-mid-IR colours, and common outflow signatures including BALs or BAL-like features and large C iv emission-line blueshifts. Their SEDs and line properties are inconsistent with normal quasars behind a dust reddening screen. We argue that the core ERQs are a unique obscured quasar population with extreme physical conditions related to powerful outflows across the line-forming regions. Patchy obscuration by small dusty clouds could produce the observed UV extinctions without substantial UV reddening.

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EP - 3463

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

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