Abstract
We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z > 0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 μm sources are selected from a Spitzer MIPS survey of the NOAO Deep Wide-Field Survey Boötes field and have corresponding 8 μm data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 to 8 μm flux ratio. The X-ray-detected sources fall within the peak corresponding to a flat spectrum in vf v, implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 to 8 μm flux ratio is likely due to LIRGs whose IR emission is powered by starbursts. The 24 μm emission is increasingly dominated by AGN at higher 24 μm flux densities (f 24): the AGN fraction of the z > 0.6 sources increases from 9% at f24 ≈ 0.35 mJy to 74% ±20% at f24 ≈ 3 mJy, in good agreement with model predictions. Deep 24 μm, small-area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ∼3%-7% of the total 24 μm background.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 143-147 |
| Number of pages | 5 |
| Journal | Astrophysical Journal |
| Volume | 644 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jun 10 2006 |
| Externally published | Yes |
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Keywords
- Galaxies: active
- Galaxies: starburst
- Infrared: galaxies
- X-rays
ASJC Scopus subject areas
- Space and Planetary Science
Cite this
The active galactic nuclei contribution to the mid-infrared emission of luminous infrared galaxies. / Brand, K.; Dey, A.; Weedman, D.; Desai, V.; Floc'H, E. L E; Jannuzi, Buell Tomasson; Soifer, B. T.; Brown, M. J I; Eisenhardt, P.; Gorjian, V.; Papovich, C.; Smith, H. A.; Willner, S. P.; Cool, R. J.
In: Astrophysical Journal, Vol. 644, No. 1, 10.06.2006, p. 143-147.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The active galactic nuclei contribution to the mid-infrared emission of luminous infrared galaxies
AU - Brand, K.
AU - Dey, A.
AU - Weedman, D.
AU - Desai, V.
AU - Floc'H, E. L E
AU - Jannuzi, Buell Tomasson
AU - Soifer, B. T.
AU - Brown, M. J I
AU - Eisenhardt, P.
AU - Gorjian, V.
AU - Papovich, C.
AU - Smith, H. A.
AU - Willner, S. P.
AU - Cool, R. J.
PY - 2006/6/10
Y1 - 2006/6/10
N2 - We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z > 0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 μm sources are selected from a Spitzer MIPS survey of the NOAO Deep Wide-Field Survey Boötes field and have corresponding 8 μm data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 to 8 μm flux ratio. The X-ray-detected sources fall within the peak corresponding to a flat spectrum in vf v, implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 to 8 μm flux ratio is likely due to LIRGs whose IR emission is powered by starbursts. The 24 μm emission is increasingly dominated by AGN at higher 24 μm flux densities (f 24): the AGN fraction of the z > 0.6 sources increases from 9% at f24 ≈ 0.35 mJy to 74% ±20% at f24 ≈ 3 mJy, in good agreement with model predictions. Deep 24 μm, small-area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ∼3%-7% of the total 24 μm background.
AB - We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z > 0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 μm sources are selected from a Spitzer MIPS survey of the NOAO Deep Wide-Field Survey Boötes field and have corresponding 8 μm data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 to 8 μm flux ratio. The X-ray-detected sources fall within the peak corresponding to a flat spectrum in vf v, implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 to 8 μm flux ratio is likely due to LIRGs whose IR emission is powered by starbursts. The 24 μm emission is increasingly dominated by AGN at higher 24 μm flux densities (f 24): the AGN fraction of the z > 0.6 sources increases from 9% at f24 ≈ 0.35 mJy to 74% ±20% at f24 ≈ 3 mJy, in good agreement with model predictions. Deep 24 μm, small-area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ∼3%-7% of the total 24 μm background.
KW - Galaxies: active
KW - Galaxies: starburst
KW - Infrared: galaxies
KW - X-rays
UR - http://www.scopus.com/inward/record.url?scp=33747070759&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33747070759&partnerID=8YFLogxK
U2 - 10.1086/503416
DO - 10.1086/503416
M3 - Article
AN - SCOPUS:33747070759
VL - 644
SP - 143
EP - 147
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
ER -