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Herschel Spectroscopic Observations of LITTLE THINGS Dwarf Galaxies

Cigan, Phil and Young, Lisa and Cormier, Diane and Lebouteiller, Vianney and Madden, Suzanne and Hunter, Deidre and Brinks, Elias and Elmegreen, Bruce and Schruba, Andreas and Heesen, Volker (2016) Herschel Spectroscopic Observations of LITTLE THINGS Dwarf Galaxies. Astronomical Journal, 151 (1). Art. No. 14. ISSN 1538-3881. doi:10.3847/0004-6256/151/1/14.

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We present far-infrared (FIR) spectral line observations of five galaxies from the Little Things sample: DDO 69, DDO 70, DDO 75, DDO 155, and WLM. While most studies of dwarfs focus on bright systems or starbursts due to observational constraints, our data extend the observed parameter space into the regime of low surface brightness dwarf galaxies with low metallicities and moderate star formation rates. Our targets were observed with Herschel at the [C ii] 158 μm, [O i] 63 μm, [O iii] 88 μm, and [N ii] 122 μm emission lines using the PACS Spectrometer. These high-resolution maps allow us for the first time to study the FIR properties of these systems on the scales of larger star-forming complexes. The spatial resolution in our maps, in combination with star formation tracers, allows us to identify separate photodissociation regions (PDRs) in some of the regions we observed. Our systems have widespread [C ii] emission that is bright relative to continuum, averaging near 0.5% of the total infrared (TIR) budget—higher than in solar-metallicity galaxies of other types. [N ii] is weak, suggesting that the [C ii] emission in our galaxies comes mostly from PDRs instead of the diffuse ionized interstellar medium (ISM). These systems exhibit efficient cooling at low dust temperatures, as shown by ([O i]+[C ii])/TIR in relation to 60 μm/100 μm, and low [O i]/[C ii] ratios which indicate that [C ii] is the dominant coolant of the ISM. We observe [O iii]/[C ii] ratios in our galaxies that are lower than those published for other dwarfs, but similar to levels noted in spirals.

Item Type:Article
Related URLs:
URLURL TypeDescription
Hunter, Deidre0000-0002-3322-9798
Brinks, Elias0000-0002-7758-9699
Elmegreen, Bruce0000-0002-1723-6330
Additional Information:© 2016. The American Astronomical Society. Received 2014 December 31; accepted 2015 September 25; published 2016 January 4. Funding for this project was provided by NASA JPL RSA grant 1433776. S.C.M. acknowledges support from the Agence Nationale de la Recherche (ANR) through the programme SYMPATICO (Program Blanc Projet ANR-11-BS56-0023). V.H. acknowledges support from the Science and Technology Facilities Council (STFC) under grant ST/J001600/1. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. E.B. acknowledges support from the UK's Science and Technology Facilities Council [grant numbers ST/J001333/1, ST/M001008/1]. Facilities: Herschel (PACS), VLA
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agence Nationale pour la Recherche (ANR)ANR-11-BS56-0023
Science and Technology Facilities Council (STFC)ST/J001600/1
Science and Technology Facilities Council (STFC)ST/J001333/1
Science and Technology Facilities Council (STFC)ST/M001008/1
Subject Keywords:galaxies: dwarf; galaxies: individual (DDO 69, DDO 70, DDO 75, DDO 155, WLM) ; galaxies: ISM
Issue or Number:1
Record Number:CaltechAUTHORS:20160205-101345124
Persistent URL:
Official Citation:Phil Cigan et al 2016 The Astronomical Journal 151 14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64267
Deposited By: George Porter
Deposited On:08 Feb 2016 19:23
Last Modified:10 Nov 2021 23:28

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