Astrophys. J., 846, 32-32 (2017/September-1)
A Herschel/PACS far-infrared line emission survey of local luminous infrared galaxies.
DIAZ-SANTOS T., ARMUS L., CHARMANDARIS V., LU N., STIERWALT S., STACEY G., MALHOTRA S., VAN DER WERF P.P., HOWELL J.H., PRIVON G.C., MAZZARELLA J.M., GOLDSMITH P.F., MURPHY E.J., BARCOS-MUNOZ L., LINDEN S.T., INAMI H., LARSON K.L., EVANS A.S., APPLETON P., IWASAWA K., LORD S., SANDERS D.B. and SURACE J.A.
Abstract (from CDS):
We present an analysis of [OI]63, [O III]88, [N II]122, and [CII]158 far-infrared (FIR) fine-structure line observations obtained with Herschel/PACS, for ∼240 local luminous infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey. We find pronounced declines ("deficits") of line-to-FIR continuum emission for [N II]122, [OI]63, and [CII]158 as a function of FIR color and infrared luminosity surface density, ΣIR. The median electron density of the ionized gas in LIRGs, based on the [N II]122/[N II]205 ratio, is ne = 41 cm–3. We find that the dispersion in the [CII]158 deficit of LIRGs is attributed to a varying fractional contribution of photodissociation regions (PDRs) to the observed [CII]158 emission, f([C II]158PDR) = [C II]158PDR/[CII]158, which increases from ∼60% to ∼95% in the warmest LIRGs. The [OI]63/[C II]158PDR ratio is tightly correlated with the PDR gas kinetic temperature in sources where [OI]63 is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, nH, and intensity of the interstellar radiation field, G, in units of G0 and find G/nH ratios of ∼0.1-50 G0 cm3, with ULIRGs populating the upper end of the distribution. There is a relation between G/nH and ΣIR, showing a critical break at ΣIR* ≃ 5 x 1010 L☉ kpc–2. Below ΣIR* , G/nH remains constant, ≃0.32 G0 cm3, and variations in ΣIR are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. Above ΣIR* , G/nH increases rapidly with ΣIR, signaling a departure from the typical PDR conditions found in normal star-forming galaxies toward more intense/harder radiation fields and compact geometries typical of starbursting sources.
© 2017. The American Astronomical Society. All rights reserved.
galaxies: evolution - galaxies: ISM - galaxies: nuclei - galaxies: starburst - infrared: galaxies - infrared: galaxies
VizieR on-line data:
<Available at CDS (J/ApJ/846/32): galaxies.dat table1.dat table2.dat>
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