2001A&A...367L...9H


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.09CET22:58:38

2001A&A...367L...9H - Astronomy and Astrophysics, volume 367, L9-13 (2001/3-1)

The PAH 7.7µm/850µm ratio as new diagnostics for high extinction in ULIRGs - increasing evidence for a hidden quasar in Arp 220.

HAAS M., KLAAS U., MUELLER S.A.H., CHINI R. and COULSON I.

Abstract (from CDS):

A new method is presented to reveal high mid-infrared (MIR) extinction in ultraluminous infrared galaxies (ULIRGs): the ratio between the PAH 7.7µm feature and the sub-mm continuum at 850µm. While the sub-mm radiation is optically thin and serves for normalization, any high MIR extinction reduces the observed PAH 7.7µm strength. Since the emitters (PAH carriers) and the absorbers (large dust grains reemitting at 850µm) are typically mixed along the line of sight, the new method probes the absorption along the entire dust column, and not only the properties of a shallow surface. 13 out of a sample of 15 ULIRGs as well as 20 normal galaxies of a comparison sample populate the same well confined range of the PAH 7.7µm/850µm flux ratio (4±2). Their MIR extinction may be moderate. In contrast, two ULIRGs show an exceptionally low PAH 7.7µm/850 µm ratio indicative of high extinction: UGC 5101 has AV(mixed)≃50 consistent with former spectroscopic estimates. Arp 220 has a huge extinction of at least AV(mixed)≃110, exceeding former estimates of AV(screen) > 45 based on the [SIII] 18.7µm/33.5µm ratio. As an application of the new diagnostics, after dereddening of the central MIR continuum and with the assumption of a disk-like dust distribution seen under a tilted angle, we find increasing evidence for a hidden quasar in Arp 220.

Abstract Copyright:

Journal keyword(s): ISM: dust extinction - galaxies: individual: Arp 220 - ISM - quasars - starburst - infrared: galaxies

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10608 1
2 UGC 5101 Sy1 09 35 51.694 +61 21 10.52   15.20 15.50     ~ 500 4
3 Mrk 231 Sy1 12 56 14.2340989340 +56 52 25.238555193   14.68 13.84     ~ 1742 3
4 Mrk 273 Sy2 13 44 42.070 +55 53 13.17   15.68 14.91     ~ 814 3
5 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2629 4
6 NGC 6240 Sy2 16 52 58.861 +02 24 03.55   14.31 13.37     ~ 1450 2
7 Mrk 518 G 21 58 35.984 +12 02 20.22   14.3       ~ 36 0

    Equat.    Gal    SGal    Ecl

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2019.12.09-22:58:38

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