TY - JOUR
T1 - Disentangling AGN and star formation activity at high redshift using hubble space telescope grism spectroscopy
AU - Bridge, Joanna S.
AU - Zeimann, Gregory R.
AU - Trump, Jonathan R.
AU - Gronwall, Caryl
AU - Ciardullo, Robin
AU - Fox, Derek
AU - Schneider, Donald P.
N1 - Funding Information:
We thank the anonymous referee for very insightful comments. This work was partially supported by NSF through grant AST 09-26641. J.R.T. acknowledges support from NASA through Hubble Fellowship grant #51330 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. The Institute for Gravitation and the Cosmos is supported by the Eberly College of Science and the Office of the Senior Vice President for Research at The Pennsylvania State University. IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This research has made use of NASA's Astrophysics Data System Bibliographic Services.
Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved..
PY - 2016/8/1
Y1 - 2016/8/1
N2 - Differentiating between active galactic nucleus (AGN) activity and star formation in z ∼ 2 galaxies is difficult because traditional methods, such as line-ratio diagnostics, change with redshift, while multi-wavelength methods (X-ray, radio, IR) are sensitive to only the brightest AGNs. We have developed a new method for spatially resolving emission lines using the Hubble Space Telescope/Wide Field Camera 3 G141 grism spectra and quantifying AGN activity through the spatial gradient of the [O iii]/Hβ line ratio. Through detailed simulations, we show that our novel line-ratio gradient approach identifies ∼40% more low-mass and obscured AGNs than obtained by classical methods. Based on our simulations, we developed a relationship that maps the stellar mass, star formation rate, and measured [O iii]/Hβ gradient to the AGN Eddington ratio. We apply our technique to previously studied stacked samples of galaxies at z ∼ 2 and find that our results are consistent with these studies. This gradient method will also be able to inform other areas of galaxy evolution science, such as inside-out quenching and metallicity gradients, and will be widely applicable to future spatially resolved James Webb Space Telescope data.
AB - Differentiating between active galactic nucleus (AGN) activity and star formation in z ∼ 2 galaxies is difficult because traditional methods, such as line-ratio diagnostics, change with redshift, while multi-wavelength methods (X-ray, radio, IR) are sensitive to only the brightest AGNs. We have developed a new method for spatially resolving emission lines using the Hubble Space Telescope/Wide Field Camera 3 G141 grism spectra and quantifying AGN activity through the spatial gradient of the [O iii]/Hβ line ratio. Through detailed simulations, we show that our novel line-ratio gradient approach identifies ∼40% more low-mass and obscured AGNs than obtained by classical methods. Based on our simulations, we developed a relationship that maps the stellar mass, star formation rate, and measured [O iii]/Hβ gradient to the AGN Eddington ratio. We apply our technique to previously studied stacked samples of galaxies at z ∼ 2 and find that our results are consistent with these studies. This gradient method will also be able to inform other areas of galaxy evolution science, such as inside-out quenching and metallicity gradients, and will be widely applicable to future spatially resolved James Webb Space Telescope data.
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U2 - 10.3847/0004-637X/826/2/172
DO - 10.3847/0004-637X/826/2/172
M3 - Article
AN - SCOPUS:84982245161
SN - 0004-637X
VL - 826
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 172
ER -