View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Caltech Authors The Astrophysical Journal Supplement Series, 178:280Y301, 2008 October A # 2008. The American Astronomical Society. All rights reserved. Printed in U.S.A. A COMPENDIUM OF FAR-INFRARED LINE AND CONTINUUM EMISSION FOR 227 GALAXIES OBSERVED BY THE INFRARED SPACE OBSERVATORY James R. Brauher,1 Daniel A. Dale,2 and George Helou1 Received 2008 March 25; accepted 2008 May 19 ABSTRACT Far-infrared line and continuum fluxes are presented for a sample of 227 galaxies observed with the Long Wave- length Spectrometer on the Infrared Space Observatory. The galaxy sample includes normal star-forming systems, starbursts, and active galactic nuclei covering a wide range of colors and morphologies. The data set spans some 1300 line fluxes, 600 line upper limits, and 800 continuum fluxes. Several fine-structure emission lines are detected that arise in either photodissociation or H ii regions: [O iii]52m, [N iii]57m, [O i]63m, [O iii]88m, [N ii]122m, [O i] 145 m, and [C ii]158m. Molecular lines such as OH at 53, 79, 84, 119, and 163 m, and H 2O at 58, 66, 75, 101, and 108 m are also detected in some galaxies. In addition to those lines emitted by the target galaxies, serendipitous detec- tions of Milky Way [C ii]158m and an unidentified line near 74 m in NGC 1068 are also reported. Finally, con- tinuum fluxes at 52, 57, 63, 88, 122, 145, 158, and 170 m are derived for a subset of galaxies in which the far-infrared emission is contained within the 7500 ISO LWS beam. The statistics of this large database of continuum and line fluxes, including trends in line ratios with the far-infrared color and infrared-to-optical ratio, are explored. Subject headinggs: infrared: galaxies — infrared: ISM Online material: color figures, machine-readable tables <![%ONLINE; [toctitlegrptitleOnline Material/title/titlegrpentrytitlegrptitlefigref rid="fg13" place="NO"Figure 13/figref/title/titlegrp/entryentrytitlegrptitlefigref rid="fg14" place="NO"Figure 14/figref/title/titlegrp/entryentrytitlegrptitlefigref rid="fg15" place="NO"Figure 15/figref/title/ 1.titlegrp/entryentrytitlegrptitlefigref INTRODUCTION rid="fgHollenbach16" place="NO"Figure 1985; Rubin 1985; 16/figref/title/titlegrp/ Wolfire et al. 1990; Hollenbach entryentrytitlegrptitlefigref rid="fg17"et al.place="NO"Figure 1991; Spinoglio & Malkan 17/figref/title/titlegrp/ 1992; Rubin et al. 1994; Kaufman Far-infrared wavelengths provide the opportunity to observe entryentrytitlegrptitlefigref rid="fg18"etplace="NO"Figure al. 1999; Abel et al. 2005; 18/figref/title/titlegrp/ Le Petit et al. 2006; Meijerink et al. dust-enshrouded galaxies without large extinction effects and offer entryentrytitlegrptitlefigref rid="fg19"2007;place="NO"Figure Groves et al. 2008), these 19/figref/title/titlegrp/ fine-structure transitions can be many diagnostics of the physical conditions in the interstellar me- entryentrytitlegrptitlefigref rid="fg20"usedplace="NO"Figure to derive gas temperatures, 20/figref/title/titlegrp/ densities, and the intensity of the dium of these galaxies. The Kuiper Airborne Observatory pro- entryentrytitlegrptitlefigref rid="fg21"radiationplace="NO"Figure fields in galaxies. 21/figref/title/titlegrp/The LWS was also used to observe a vided early data on the far-infrared fine-structure lines that arise entryentrytitlegrptitlefigref rid="fg22" place="NO"Figure 22/figref/title/titlegrp/ in photodissociation regions (PDRs) and H ii regions in galaxies. suite of molecular lines in galaxies (Fischer et al. 1999) including entryentrytitlegrptitlefigref rid="fg23" place="NhydroxylO"Figure (OH 23/figref/title/titlegrp/entrylabelMachine- 53, 65, 79, 84, 119, 163 m), water (H O59,67, With the launch of the Infrared Space Observatory (ISO; Kessler 2 readable Tables/labelentrytitlegrptitletableref75, rid="tb2" 101, 108 placem),="NO"Table and the LWS range 2/tableref/title/titlegrp/ contains a plethora of high- et al. 1996, 2003) the far-infrared properties of galaxies were ob- entryentrytitlegrptitletableref rid="tb4" place="levelNO"Table rotational 4/tableref/title/titlegrp/entry/toc]]> lines of carbon monoxide (Varberg & Evenson served with greater sensitivity than ever before. The Long Wave- 1992). From the detections of multiple transitions of these mole- length Spectrometer (LWS; Clegg et al. 1996; Gry et al. 2003) on cules, the column densities and abundances for OH, H O, and CO ISO allowed the large-scale study of far-infrared atomic and mo- 2 can be determined (e.g., Skinner et al. 1997; Gonza´lez-Alfonso lecular lines that supply new insight into the understanding of the et al. 2004, 2008; Spinoglio et al. 2005). interstellar medium of these sources. Our next opportunities This contribution reports on LWS observations of seven far- for far-infrared spectroscopic studies of galaxies will come infrared fine-structure atomic and ionic lines, far-infrared lines with the Stratospheric Observatory for Infrared Astronomy and from three molecular species, and the far-infrared continuum of the Herschel Space Observatory. 227 galaxies, in addition to serendipitous detections of Milky Way The LWS data presented in this paper were taken from the ISO 3 [C ii] 158 m emission. The collection of far-infrared line fluxes archive. A variety of extragalactic observing programs used the LWS to obtain spectra of the primary diagnostic lines of the in- in this paper composes the largest sample ever assembled and re- duced in a uniform manner. These line fluxes are used to compare terstellar medium in the far-infrared. These lines include [O iii] the relationship of the far-infrared fine-structure lines, normal- 52 m, [N iii]57m, [O i]63m, [O iii]88m, [N ii]122m, ized to either another far-infrared line or the far-infrared contin- [O i] 145 m, and [C ii] 158 m. Among these atomic and ionic uum level, to two indicators of star formation activity: the 60 m/ fine-structure lines, [C ii]158m and [O i]63m are the dom- 100 m ratio and far-infraredYtoYB ratio. The properties of these inant cooling lines for neutral interstellar gas. Observations of emission lines are compared to findings from previous LWS [C ii] 158 m in NGC 6946 (Madden et al. 1993; Contursi et al. emission-line studies (Malhotra et al. 1997, 2001; Leech et al. 2002) suggest that a significant fraction of the [C ii]158m emis- 1999; Fischer et al. 1999; Luhman et al. 1998, 2003; Negishi et al. sion might also originate in diffuse ionized gas in some galaxies, 2001). The LWS continuum fluxes derived in this work are com- while the far-infrared emission lines from ionized species ([O iii] 52 m, [N iii]57m, [O iii]88m, and [N ii]122m) predomi- pared to IRAS 60 m and 100 m fluxes, ISOPHOT 170 m fluxes (Stickel et al. 2000), and infrared spectral energy distribution mod- nantly originate in H ii regions (see also Sauvage et al. 2005). els for normal star-forming galaxies (Dale & Helou 2002). Combined with models of PDRs and H ii regions (e.g., Tielens & These data can form an important framework for studies of global extragalactic interstellar media including the derivation of 1 California Institute of Technology, MC 314-6, Pasadena, CA 91101. 2 Department of Physics and Astronomy, University of Wyoming, Laramie, average gas temperatures, densities, abundances, and radiation WY 82071; [email protected]. fields integrated over entire galaxy systems. The line and contin- 3 Available online at http://www.iso.vilspa.esa.es/ida/index.html. uum fluxes presented here can also supply the data for studies of 280 COMPENDIUM OF ISO LWS EXTRAGALACTIC DATA 281 the individual components (H ii regions, spiral arms, disk regions) IRAS fluxes in Table 1 are taken from SCANPI co-additions of of large galaxies resolved by the LWS. Contursi et al. (2002), for the IRAS survey scans. example, examine the physical conditions of these different gal- The galaxies in this sample are distributed across the entire sky. axy components in NGC 1313 and NGC 6946 using PDR models Figure 1 displays the galaxy distribution in Galactic coordinates. (Kaufman et al. 1999), and L. C. Johnson et al. (in preparation) ex- The clump of galaxies at (l; b) (280; 74) is the Virgo Cluster. plore the relationships between the far- and mid-infrared cooling Approximately 40 galaxies lie within the zone of avoidance, where lines observed, respectively, by ISO and the Spitzer Space Tele- jbj < 20. Although there may be some serendipitous Galactic scope. LWS studies of individual galaxies have also been carried line and continuum emission in all directions of the sky, this ser- out for NGC 4038/4039, M 82, NGC 253, Cen A, NGC 1068, endipitous contamination is more likely toward galaxies within Arp 220, and Mrk 231 (Fischer et al. 1996; Colbert et al. 1999; the zone of avoidance in either the galaxy spectra or the spectra Unger et al. 2000; Bradford et al. 1999; Gonza´lez-Alfonso et al. of an off-source position taken during these observations. This 2004, 2008; Spinoglio et al. 2005). contamination of the observed line measurements by Milky Way Section 2 describes the sample of galaxies, while x 3 describes emission is a concern, and a discussion of detected Galactic emis- the observations and data analysis. In x 4 the far-infrared continuum sion lines is found in x 5. data are presented and assessed from comparisons to IRAS 60 and The Palomar Observatory Sky Survey plates and other ob- 100 m data, ISOPHOT 170 m data, and galaxy infrared spectral servations found within NED were used to reexamine the optical energy distribution models. The far-infrared line data and proper- morphology for each galaxy (H. Corwin 2002, private commu- ties are presented in x 5. In x 6 the statistical trends seen in the line nication).