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Title: O v] λλ1213.8,1218.3 emission from extended nebulae around quasars: contamination of Ly α and a new diagnostic for AGN activity in Ly α emitters

Abstract

ABSTRACT We investigate the potential for the emission lines O v] λλ1213.8,1218.3 and He ii λ1215.1 to contaminate flux measurements of Ly α λ1215.7 in the extended nebulae of quasars. We have computed a grid of photoionization models with a substantial range in the slope of the ionizing power law (−1.5 < α < −0.5), gas metallicity (0.01 < Z/Z⊙ < 3.0), gas density (1 < nH < 104 cm−3), and ionization parameter (10−5 < U < 1.0). We find the contribution from He ii λ1215.1 to be negligible, i.e. <0.1 of Ly α flux, across our entire model grid. The contribution from O v] λλ1213.8,1218.3 is generally negligible when U is low (≲10−3) and/or when the gas metallicity is low (Z/Z⊙ ≲ 0.1). However, at higher values of U and Z we find that O v] can significantly contaminate Ly α, in some circumstances accounting for more than half the total flux of the Ly α + He ii + O v] blend. We also provide means to estimate the fluxes of O v] λλ1213.8,1218.3 and He ii λ1215.1 by extrapolating from other lines. We estimate the fluxes of O v] and He ii for a sample of 107 Type 2 active galaxies at z > 2, and find evidence for significant (≥10 per cent) contamination of Ly α fluxes in the majoritymore » of cases (84 per cent). We also discuss prospects for using O v] λλ1213.8,1218.3 as a diagnostic for the presence of AGN activity in high-z Ly α emitters, and caution that the presence of significant O v] emission could impact the apparent kinematics of Ly α, potentially mimicking the presence of high-velocity gas outflows.« less

Authors:
 [1]
  1. Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT P-4150-762 Porto, Portugal
Publication Date:
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
OSTI Identifier:
1507809
Grant/Contract Number:  
SFRH/BPD/107919/2015; PTDC/FIS-AST/3214/2012; UID/FIS/04434/2013
Resource Type:
Journal Article: Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 486 Journal Issue: 2; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Humphrey, A. O v] λλ1213.8,1218.3 emission from extended nebulae around quasars: contamination of Ly α and a new diagnostic for AGN activity in Ly α emitters. United Kingdom: N. p., 2019. Web. doi:10.1093/mnras/stz687.
Humphrey, A. O v] λλ1213.8,1218.3 emission from extended nebulae around quasars: contamination of Ly α and a new diagnostic for AGN activity in Ly α emitters. United Kingdom. doi:10.1093/mnras/stz687.
Humphrey, A. Wed . "O v] λλ1213.8,1218.3 emission from extended nebulae around quasars: contamination of Ly α and a new diagnostic for AGN activity in Ly α emitters". United Kingdom. doi:10.1093/mnras/stz687.
@article{osti_1507809,
title = {O v] λλ1213.8,1218.3 emission from extended nebulae around quasars: contamination of Ly α and a new diagnostic for AGN activity in Ly α emitters},
author = {Humphrey, A.},
abstractNote = {ABSTRACT We investigate the potential for the emission lines O v] λλ1213.8,1218.3 and He ii λ1215.1 to contaminate flux measurements of Ly α λ1215.7 in the extended nebulae of quasars. We have computed a grid of photoionization models with a substantial range in the slope of the ionizing power law (−1.5 < α < −0.5), gas metallicity (0.01 < Z/Z⊙ < 3.0), gas density (1 < nH < 104 cm−3), and ionization parameter (10−5 < U < 1.0). We find the contribution from He ii λ1215.1 to be negligible, i.e. <0.1 of Ly α flux, across our entire model grid. The contribution from O v] λλ1213.8,1218.3 is generally negligible when U is low (≲10−3) and/or when the gas metallicity is low (Z/Z⊙ ≲ 0.1). However, at higher values of U and Z we find that O v] can significantly contaminate Ly α, in some circumstances accounting for more than half the total flux of the Ly α + He ii + O v] blend. We also provide means to estimate the fluxes of O v] λλ1213.8,1218.3 and He ii λ1215.1 by extrapolating from other lines. We estimate the fluxes of O v] and He ii for a sample of 107 Type 2 active galaxies at z > 2, and find evidence for significant (≥10 per cent) contamination of Ly α fluxes in the majority of cases (84 per cent). We also discuss prospects for using O v] λλ1213.8,1218.3 as a diagnostic for the presence of AGN activity in high-z Ly α emitters, and caution that the presence of significant O v] emission could impact the apparent kinematics of Ly α, potentially mimicking the presence of high-velocity gas outflows.},
doi = {10.1093/mnras/stz687},
journal = {Monthly Notices of the Royal Astronomical Society},
issn = {0035-8711},
number = 2,
volume = 486,
place = {United Kingdom},
year = {2019},
month = {4}
}

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