ALMA and Herschel reveal that X-ray-selected AGN and main-sequence galaxies have different star formation rate distributions

Journal
Date Issued
2015
Author(s)
Mullaney, J. R.
•
Alexander, D. M.
•
Aird, J.
•
Bernhard, E.
•
Daddi, E.
•
Del Moro, A.
•
Dickinson, M.
•
Elbaz, D.
•
Harrison, C. M.
•
Juneau, S.
•
Liu, D.
•
•
Rosario, D.
•
•
Sargent, M.
•
Schreiber, C.
•
Simpson, J.
•
Stanley, F.
DOI
Description
We thank the anonymous referee. DMA, ADM, CMH acknowledge STFC grant ST/I001573/1. This Letter makes use of ALMA data: ADS/JAO.ALMA#2012.1.00869.S.
Abstract
Using deep Herschel and ALMA observations, we investigate the star formation rate (SFR) distributions of X-ray-selected active galactic nucleus (AGN) host galaxies at 0.5 < z < 1.5 and 1.5 < z < 4, comparing them to that of normal, star-forming (i.e. `main-sequence', or MS) galaxies. We find that 34-55 per cent of AGNs in our sample have SFRs at least a factor of 2 below that of the average MS galaxy, compared to ≈15 per cent of all MS galaxies, suggesting significantly different SFR distributions. Indeed, when both are modelled as lognormal distributions, the mass and redshift-normalized SFR distributions of X-ray AGNs are roughly twice as broad, and peak ≈0.4 dex lower, than that of MS galaxies. However, like MS galaxies, the normalized SFR distribution of AGNs in our sample appears not to evolve with redshift. Despite X-ray AGNs and MS galaxies having different SFR distributions, the linear-mean SFR of AGNs derived from our distributions is remarkably consistent with that of MS galaxies, and thus with previous results derived from stacked Herschel data. This apparent contradiction is due to the linear-mean SFR being biased by bright outliers, and thus does not necessarily represent a true characterization of the typical SFR of X-ray AGNs.
Volume
453
Issue
1
Start page
L83
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.453L..83M
Rights
open.access
File(s)
Loading...
Thumbnail Image
Name

mullaney15_open.pdf

Description
postprint
Size

329.06 KB

Format

Adobe PDF

Checksum (MD5)

886f8c63ee660146e1e346782252647b

Loading...
Thumbnail Image
Name

mullaney15.pdf

Description
Pdf editoriale
Size

844.28 KB

Format

Adobe PDF

Checksum (MD5)

0b6e62806bca55180659113f93debd1d