J/MNRAS/495/4707 Carbon-loud SDSS BOSS type II quasars at z>2 (Silva+, 2020)
Carbon-loud SDSS BOSS type II quasars at z > 2: high-density gas or secondary
production of carbon?
Silva M., Humphrey A., Lagos P., Morais S.G.
<Mon. Not. R. Astron. Soc., 495, 4707-4746 (2020)>
=2020MNRAS.495.4707S 2020MNRAS.495.4707S (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Active gal. nuclei ; Redshifts ; Spectroscopy ;
Ultraviolet ; Optical
Keywords: galaxies: active - galaxies: evolution - galaxies: high-redshift -
galaxies: ISM
Abstract:
We study the ultraviolet (UV) emission-line ratios of a sample of 145
type II quasars (QSO2s) from Sloan Digital Sky Survey III Baryon
Oscillation Spectroscopic Survey, and compare against a grid of active
galactic nucleus (AGN) photoionization models with a range in gas
density, gas chemical abundances, and ionization parameter. Most of
the quasars are 'carbon-loud', with CIV/HeII ratios that are unusually
high for the narrow-line region, implying higher than expected gas
density (>106cm-3) and/or significantly supersolar-relative carbon
abundance. We also find that solar or supersolar nitrogen abundance
and metallicity are required in the majority of our sample, with
potentially significant variation between objects. Compared to radio
galaxies at similar redshifts (HzRGs; z>2), the QSO2s are offset to
higher NV/HeII, CIV/HeII, and CIII/HeII, suggesting systematically
higher gas density and/or systematically higher C and N abundances. We
find no evidence for a systematic difference in the N/C abundance
ratio between the two types of objects. Scatter in the NIV/CIV ratio
implies a significant scatter in the N/C abundance ratio among the
QSO2s and HzRGs, consistent with differences in the chemical
enrichment histories between objects. Interestingly, we find that
adopting secondary behaviour for both N and C alleviates the
long-standing 'NIV problem'. A subset of the QSO2s and HzRGs also
appear to be 'silicon-loud', with SiIII relative fluxes suggesting
Si/C and Si/O are an order of magnitude above their solar values.
Finally, we propose new UV-line criteria to select genuine QSO2s with
low-density narrow-line regions.
Description:
The objects studied in this paper are a subsample of quasars from the
spectroscopic quasar sample of the BOSS of the SDSS Data Release 9
(see Gunn et al. 2006AJ....131.2332G 2006AJ....131.2332G; Alexandroff et al.
2013MNRAS.435.3306A 2013MNRAS.435.3306A, Cat. J/MNRAS/435/3306 and references therein).
Alexandroff et al. (2013MNRAS.435.3306A 2013MNRAS.435.3306A, Cat. J/MNRAS/435/3306)
selected 452 candidate QSO2s in the redshift range 2.0<z<4.3, using
selection criteria that included 5σ detections in both Lyα
and CIV, with both lines also requiring to have full width at
half-maximum (FWHM)<2000km/s. In this study, we consider only the 145
type II Class A quasar candidates of Alexandroff et al.
(2013MNRAS.435.3306A 2013MNRAS.435.3306A, Cat. J/MNRAS/435/3306), in order to avoid
unnecessary contamination from unobscured objects.
In addition, we make use of rest-frame optical line fluxes of QSO2
candidates published by Greene et al. (2014ApJ...788...91G 2014ApJ...788...91G), who used
Triplespec on the Apache Point Observatory 3.5-m Telescope (APO),
Folded-port Infrared Echellete (FIRE) on the 6.5-m Baade-Magellan
Telescope, and the Gemini Near-Infrared Spectrograph (GNIRS) on the
Gemini North 8.1-m Telescope. The sample of Greene et al.
(2014ApJ...788...91G 2014ApJ...788...91G) consists of 19 candidate QSO2s at 2.0<z<3.4;
here we use the line fluxes of 16 candidate QSO2s which are also
present in the Class A subsample discussed above.
As a comparison sample, we used emission-line fluxes of HzRGs at
2.27=<z=<3.56 from the literature (see Table A1). The objects were
observed using the Low Resolution Imaging Spectrometer (LRIS) in
spectropolarimetry mode at the Keck II 10-m telescope, the Infrared
Spectrometer and Array Camera (ISAAC) in long-slit mode, and Focal
Reducer and Spectrograph (FORS1) at the Very Large Telescope (VLT), OH
Airglow Suppressor (OHS) spectrograph mounted on the Subaru telescope,
and ESO Multi-Mode Instrument (EMMI) at the New Technology Telescope
(NTT).
We also include four 'core extremely red quasars' (core-ERQs; see Ross
et al. 2015MNRAS.453.3932R 2015MNRAS.453.3932R, Zakamska et al. 2016MNRAS.459.3144Z 2016MNRAS.459.3144Z,
Hamann et al. 2017MNRAS.464.3431H 2017MNRAS.464.3431H, Cat. J/MNRAS/464/3431, Villar
Martin et al. 2020A&A...634A.116V 2020A&A...634A.116V) in the redshift range 2.3<z<2.6.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 176 13 List of flux ratios measurements of the
rest-frame UV and optical of HzRGs from the
literature
tablea2.dat 166 40 List of the first 40 type II quasars followed
by the detected emission lines
tablea7.dat 88 98 List of objects separated according to the
selection criteria presented in Section 6
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See also:
J/MNRAS/435/3306 : Candidate type II QSOs in SDSS III (Alexandroff+, 2013)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Source name
11- 13 A3 --- Ref References (1)
15- 18 F4.2 --- z Redshift
20- 23 F4.2 --- OVI+CII/HeII ? (OVI+CII)/HeII flux ratio
25- 28 F4.2 --- e_OVI+CII/HeII ? Error on OVI+CII/HeII
30- 34 F5.2 --- Lya/HeII Lyα/HeII flux ratio
36- 40 F5.2 --- e_Lya/HeII Error on Lya/HeII
42 A1 --- l_NV/HeII Limit flag on NV/HeII
44- 47 F4.2 --- NV/HeII NV/HeII flux ratio
49- 52 F4.2 --- e_NV/HeII ? Error on NV/HeII
54- 57 F4.2 --- SiIV+OIV/HeII ? (SiIV+OIV)/HeII flux ratio
59- 62 F4.2 --- e_SiIV+OIV/HeII ? Error on SiIV+OIV/HeII
64 A1 --- l_NIV/HeII Limit flag on NIV/HeII
66- 69 F4.2 --- NIV/HeII ? NIV/HeII flux ratio
71- 74 F4.2 --- e_NIV/HeII ? Error on NIV/HeII
76- 79 F4.2 --- CIV/HeII CIV/HeII flux ratio
81- 84 F4.2 --- e_CIV/HeII Error on CIV/HeII
86- 89 F4.2 --- NeIV1602/HeII ? [NeIV]1602/HeII flux ratio
91- 94 F4.2 --- OIII/HeII ? OIII/HeII flux ratio
96- 99 F4.2 --- e_OIII/HeII ? Error on OIII/HeII
101- 104 F4.2 --- SiIII/HeII ? SiIII/HeII flux ratio
106- 109 F4.2 --- e_SiIII/HeII ? Error on SiIII/HeII
111- 114 F4.2 --- CIII/HeII ? CIII/HeII flux ratio
116- 119 F4.2 --- e_CIII/HeII ? Error on CIII/HeII
121- 124 F4.2 --- NeIV2422/HeII ? [NeIV]2422/HeII flux ratio
126- 129 F4.2 --- e_NeIV2422/HeII ? Error on NeIV2422/HeII
131- 134 F4.2 --- OIII/Ha ? OIII/Hα flux ratio
136- 139 F4.2 --- e_OIII/Ha ? Error on OIII/Ha
141 A1 --- l_OIII/Hb Limit flag on OIII/Hb
143- 147 F5.2 --- OIII/Hb ? OIII/Hβ flux ratio
149- 152 F4.2 --- e_OIII/Hb ? Error on OIII/Hb
154 A1 --- l_NII/Ha Limit flag on NII/Ha
156- 159 F4.2 --- NII/Ha ? NII/Hα flux ratio
161- 164 F4.2 --- e_NII/Ha ? Error on NII/Ha
166 A1 --- l_OII/OIII Limit flag on OII/OIII
168- 171 F4.2 --- OII/OIII ? [OII]3728/[OIII]5008 flux ratio
173- 176 F4.2 --- e_OII/OIII ? Error on OII/OIII
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Note (1): References as follows:
a = Vernet et al. (2001A&A...366....7V 2001A&A...366....7V)
b = Humphrey et al. (2008MNRAS.383...11H 2008MNRAS.383...11H)
c = Silva et al. (2018MNRAS.474.3649S 2018MNRAS.474.3649S)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Source name (JHHMMSS.ss+DDMMSS.s)
21- 24 F4.2 --- z Redshift
26 I1 --- Class ? QSO classification (G1)
28- 32 F5.1 10-20W/m2 FOVI+CII ? OVI+CII emission line flux
34- 37 F4.1 10-20W/m2 e_FOVI+CII ? Error on FOVI+CII
39- 44 F6.1 10-20W/m2 FLya Lyα emission line flux
46- 49 F4.1 10-20W/m2 e_FLya Error on FLya
51- 55 F5.1 10-20W/m2 FNV ? NV emission line flux
57- 59 F3.1 10-20W/m2 e_FNV ? Error on FNV
61- 64 F4.1 10-20W/m2 FOI ? OI emission line flux
66- 68 F3.1 10-20W/m2 e_FOI ? Error on FOI
70- 73 F4.1 10-20W/m2 FSiIV+OIV ? SiIV+OIV emission line flux
75- 77 F3.1 10-20W/m2 e_FSiIV+OIV ? Error on FSiIV+OIV
79- 82 F4.1 10-20W/m2 FNIV ? NIV emission line flux
84- 86 F3.1 10-20W/m2 e_FNIV ? Error on FNIV
88- 92 F5.1 10-20W/m2 FCIV CIV emission line flux
94- 96 F3.1 10-20W/m2 e_FCIV Error on FCIV
98 A1 --- l_FNeIV1602 Limit flag on FNeIV1602
100- 103 F4.1 10-20W/m2 FNeIV1602 ? [NeIV]1602 emission line flux
105- 107 F3.1 10-20W/m2 e_FNeIV1602 ? Error on FNeIV1602
109- 112 F4.1 10-20W/m2 FHeII ? HeII emission line flux
114- 116 F3.1 10-20W/m2 e_FHeII ? Error on FHeII
118- 121 F4.1 10-20W/m2 FOIII ? OIII emission line flux
123- 125 F3.1 10-20W/m2 e_FOIII ? Error on FOIII
127- 130 F4.1 10-20W/m2 FSiIII ? SiIII emission line flux
132- 134 F3.1 10-20W/m2 e_FSiIII ? Error on SiIII
136- 140 F5.1 10-20W/m2 FCIII ? CIII emission line flux
142- 144 F3.1 10-20W/m2 e_FCIII ? Error on FCIII
146 A1 --- l_FNeIV2422 Limit flag on FNeIV2422
148- 151 F4.1 10-20W/m2 FNeIV2422 ? [NeIV]2422 emission line flux
153- 155 F3.1 10-20W/m2 e_FNeIV2422 ? Error on FNeIV2422
157- 161 F5.1 10-20W/m2 FMgII ? MgII emission line flux
163- 166 F4.1 10-20W/m2 e_FMgII ? Error on MgII
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Byte-by-byte Description of file: tablea7.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Source name (JHHMMSS.ss+DDMMSS.s)
21- 24 F4.2 --- z Redshift
26 I1 --- Class ? QSO classification (G1)
28- 32 F5.2 --- NV/HeII ? NV/HeII flux ratio
34- 37 F4.2 --- e_NV/HeII ? Error on NV/HeII
39- 43 F5.2 --- CIV/HeII CIV/HeII flux ratio
45- 48 F4.2 --- e_CIV/HeII Error on CIV/HeII
50 A1 --- l_NeIV2422/HeII Limit flag on NeIV2422/HeII
52- 55 F4.2 --- NeIV2422/HeII ? NeIV2422/HeII flux ratio
57- 60 F4.2 --- e_NeIV2422/HeII ? Error on NeIV2422/HeII
62 A1 --- l_NeIV2422/CIV Limit flag NeIV2422/CIV
64- 67 F4.2 --- NeIV2422/CIV ? NeIV2422/CIV flux ratio
69- 72 F4.2 --- e_NeIV2422/CIV ? Error on NeIV2422/CIV
74 A1 --- l_NeIV1602/NeIV2422 Limit flag on NeIV1602/NeIV2422
76- 79 F4.2 --- NeIV1602/NeIV2422 ? NeIV1602/NeIV2422 flux ratio
81- 84 I4 km/s FWHMCIV FWHM for the CIV line
86- 88 I3 km/s e_FWHMCIV Error on FWHMCIV
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Global Notes:
Note (G1): Class as follows:
1 = Highly likely QSO2 candidates with CIV/HeII<4 and [NeIV]2422/HeII>0.4
and [NeIV]2422/CIV>0.1, consistent with low electron density
2 = Good QSO2 candidates with CIV/HeII<4, but have no useful information
from [NeIV]
3 = QSO2s with [NeIV]2422/HeII and [NeIV]2422/CIV ratios consistent with
low densities, but with CIV/HeII>4 consistent with high gas density
and/or high carbon abundance
4 = Ambiguous, potentially intermediate/high-density objects. QSO2s with
CIV/HeII>4 but [NeIV]2422/HeII<0.4 and [NeIV]2422/CIV<0.1 (or no
information about [NeIV]2422)
5 = Likely intermediate- or high-density objects. QSO2s with
[NeIV]1602/[NeIV]2422>0.5
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-Jun-2023