2012A&A...539A...8G


C.D.S. - SIMBAD4 rel 1.7 - 2020.12.03CET19:00:11

2012A&A...539A...8G - Astronomy and Astrophysics, volume 539A, 8-8 (2012/3-1)

Star-formation laws in luminous infrared galaxies. New observational constraints on models.

GARCIA-BURILLO S., USERO A., ALONSO-HERRERO A., GRACIA-CARPIO J., PEREIRA-SANTAELLA M., COLINA L., PLANESAS P. and ARRIBAS S.

Abstract (from CDS):

The observational study of star-formation relations in galaxies is central for unraveling the related physical processes that are at work on local and global scales. It is still debated whether star formation can be described by a universal law that remains valid in different populations of galaxies. We aim to expand the sample of extreme starbursts, represented by local luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs), with high-quality observations in the 1-0 line of HCN, which is taken as a proxy for the dense molecular gas content. The new data presented in this work allow us to enlarge in particular the number of LIRGs studied in HCN by a factor 3 compared to previous works. The chosen LIRG sample has a range of HCN luminosities that partly overlaps with that of the normal galaxy population. We study if a universal law can account for the star-formation relations observed for the dense molecular gas in normal star-forming galaxies and extreme starbursts and explore the validity of different theoretical prescriptions of the star-formation law. We have used the IRAM 30m telescope to observe a sample of 19 LIRGs in the 1-0 lines of CO, HCN and HCO+. The galaxies were extracted from a sample of local LIRGs with available high-quality and high-resolution images obtained at optical, near and mid IR wavelengths, which probe the star-formation activity. We therefore derived the star-formation rates using different tracers and determined the sizes of the star-forming regions of all targets. The analysis of the new data proves that the efficiency of star formation in the dense molecular gas (SFEdense) of extreme starbursts is a factor 3-4 higher compared to normal galaxies. Kennicutt-Schmidt (KS) power laws were also derived. We find a duality in KS laws that is further reinforced if we account for the likely different conversion factor for HCN (αHCN) in extreme starbursts and for the unobscured star-formation rate in normal galaxies. This result extends the more extreme bimodal behavior of star-formation laws that was derived from CO molecular lines by two recent surveys to the higher molecular densities probed by HCN lines. We compared our observations with the predictions of theoretical models in which the efficiency of star formation is determined by the ratio of a constant star-formation rate per free-fall time (SFRff) to the local free-fall time (tff). We find that it is possible to fit the observed differences in the SFEdense between normal galaxies and LIRGs/ULIRGs using a common constant SFRff and a set of physically acceptable HCN densities, but only if SFRff∼0.005-0.01 and/or if αHCN is a factor of ∼a few lower than our favored values. Star-formation recipes that explicitly depend on the galaxy global dynamical time scales do not significantly improve the fit to the new HCN data presented in this work.

Abstract Copyright:

Journal keyword(s): galaxies: ISM - radio lines: ISM - galaxies: starburst - galaxies: star formation - radio lines: galaxies

Simbad objects: 21

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Number of rows : 21

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 23 G 00 09 53.411 +25 55 25.46   12.5       ~ 286 3
2 MCG+12-02-001 G 00 54 03.943 +73 05 05.23   16       ~ 89 1
3 ZW III 35 Sy2 01 44 30.516 +17 06 09.18   15.24 14.81     ~ 225 0
4 UGC 1845 GiG 02 24 07.9832706371 +47 58 10.743777802   15.7       ~ 73 1
5 NGC 1614 AGN 04 34 00.027 -08 34 44.57   14.66 13.99     ~ 606 0
6 UGC 3351 Sy2 05 45 47.836 +58 42 03.83   16.0       ~ 90 2
7 NGC 2388 GiG 07 28 53.4530354679 +33 49 08.550019911   14.7       ~ 119 2
8 MCG+02-20-003 GiG 07 35 43.416 +11 42 35.29   15.0       ~ 59 0
9 QSO J0831+5245 QSO 08 31 41.7095363198 +52 45 17.620340544   19.2   14.5 13.9 ~ 493 1
10 NGC 2623 LIN 08 38 24.016 +25 45 16.29 14.10 13.99 13.36     ~ 437 1
11 NGC 3110 H2G 10 04 02.124 -06 28 29.12   13.4   13.3 12.5 ~ 143 3
12 NVSS J102000+081335 rG 10 20 00.204 +08 13 33.78   17.5       ~ 143 1
13 IC 860 LIN 13 15 03.51 +24 37 07.8   14.8       ~ 181 0
14 NGC 5653 H2G 14 30 10.411 +31 12 55.86   12.7       ~ 158 0
15 NGC 5936 H2G 15 30 00.846 +12 59 21.55   13.0       ~ 150 1
16 IC 4553 SyG 15 34 57.22396 +23 30 11.6084   14.76 13.88     ~ 2709 4
17 LEDA 59990 H2G 17 16 35.7 -10 20 38   15.53       ~ 109 0
18 2MASX J18113842+0131397 G 18 11 38.423 +01 31 39.75           ~ 44 0
19 NGC 6701 G 18 43 12.429 +60 39 12.13   12.9       ~ 117 1
20 2MASX J20572362+1707445 PaG 20 57 23.628 +17 07 44.60   15.2       ~ 145 0
21 NGC 7591 SyG 23 18 16.2683208567 +06 35 09.111064142   13.8       ~ 228 0

    Equat.    Gal    SGal    Ecl

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2020.12.03-19:00:11

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