2022A&A...663A..46G


Query : 2022A&A...663A..46G

2022A&A...663A..46G - Astronomy and Astrophysics, volume 663A, 46-46 (2022/7-1)

A technique to select the most obscured galaxy nuclei.

GARCIA-BERNETE I., RIGOPOULOU D., AALTO S., SPOON H.W.W., HERNAN-CABALLERO A., EFSTATHIOU A., ROCHE P.F. and KONIG S.

Abstract (from CDS):

Compact obscured nuclei (CONs) are mainly found in local luminous and ultraluminous infrared galaxies (U/LIRGs). In the local Universe, these sources are generally selected through the detection of the HCN-vib (3-2) emission line at submillimetre wavelengths. In this work, we present a diagnostic method to select deeply buried nuclei based on mid-infrared (mid-IR) polycyclic aromatic hydrocarbons (PAHs) and mid-IR continuum ratios. Using Spitzer InfraRed Spectrograph (IRS) spectra of a representative sample of local ULIRGs (z < 0.27), we examine their PAH and underlying continuum emission ratios. For deeply embedded sources, we find that the 9.7 µm silicate absorption band has a particularly pronounced effect on the 11.3 µm PAH feature. The low flux level in the nuclear silicate absorption band enhances the 11.3 µm PAH feature contrast (high PAH equivalent width) compared to that of the other PAH features. The technique has been extended to include the use of the underlying 11.3/12.7 and 11.3/6.2 µm continuum ratios. However, the latter are affected by the extinction coming from both the host galaxy and the nuclear region, whereas the foreground (host-galaxy) extinction is cancelled out when using the PAH equivalent width ratios. We apply our method to local U/LIRGs from the HERUS and GOALS samples and classify 14 ULIRGs and 10 LIRGs as CON candidates, which corresponds to 30% of the ULIRGs and 7% of the LIRGs from these samples. We find that the observed continuum ratios of CON-dominated sources can be explained by assuming torus models with a tapered disc geometry and a smooth dust distribution. This suggests that the nuclear dusty structure of deeply obscured galaxy nuclei has an extremely high dust coverage. Finally, we demonstrate that the use of mid-IR colour-colour diagrams is an effective way to select CON-dominated sources at different redshifts. In particular, the combination of filters of the James Webb Space Telescope/Mid-Infrared Instrument will enable the selection of CONs out to z ∼ 1.5. This will allow the selection of CONs to be extended to high redshifts where U/LIRGs are more numerous.

Abstract Copyright: © ESO 2022

Journal keyword(s): galaxies: nuclei - galaxies: ISM - infrared: galaxies - techniques: spectroscopic

Simbad objects: 12

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Number of rows : 12
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NAME IRAS F08572+3915 NW LIN 09 00 25.364 +39 03 54.23     16.66     ~ 419 1
2 ESO 320-30 EmG 11 53 11.722 -39 07 48.72   13.30   11.86   ~ 186 1
3 NGC 4355 Sy2 12 26 54.6206739120 -00 52 39.421212996   14.21 13.37     ~ 489 2
4 3C 273 BLL 12 29 06.6998257176 +02 03 08.597629980   13.05 14.830 14.11   ~ 5797 1
5 Mrk 463 Sy2 13 56 02.9 +18 22 18   14.8 14.22     ~ 389 2
6 LEDA 52270 Sy1 14 37 38.2867288488 -15 00 24.087592692   16.58 16.40     ~ 276 1
7 Z 49-57 GiC 15 13 13.0927 +07 13 31.850   15.5       ~ 238 1
8 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2957 4
9 LEDA 60189 LIN 17 23 21.943 -00 17 00.96   15.1       ~ 424 0
10 2MFGC 14160 GiG 18 00 31.919 -04 00 53.36   17.62       ~ 64 0
11 NAME South America H2G 22 51 49.307 -17 52 23.96   16.97       ~ 327 3
12 NAME Local Group GrG ~ ~           ~ 8378 0

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