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High-J CO Versus Far-Infrared Relations in Normal and Starburst Galaxies

Liu, Daizhong and Gao, Yu and Isaak, Kate and Daddi, Emanuele and Yang, Chentao and Lu, Nanyao and van der Werf, Paul (2015) High-J CO Versus Far-Infrared Relations in Normal and Starburst Galaxies. Astrophysical Journal, 810 (2). Art. No. L14. ISSN 0004-637X.

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We present correlations between 9 CO transitions (J=4-3 to 12-11) and beam-matched far-infrared (far-IR) luminosities (L_(FIR,b) among 167 local galaxies, using Herschel Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE; FTS) spectroscopic data and Photoconductor Array Camera and Spectrometer (PACS) photometry data. We adopt entire-galaxy FIR luminosities (L_(FIR,e) from the IRAS Revised Bright Galaxy Sample and correct to L_(FIR,b) using PACS images to match the varying FTS beam sizes. All 9 correlations between L'_(CO) and L_(FIR,b) are essentially linear and tight (σ = 0.2-0.3dex dispersion), even for the highest transition, J = 12–11. This supports the notion that the star formation rate (SFR) is linearly correlated with the dense molecular gas n_H_2 ≳ 10^(4-6) cm^(-3). We divide the entire sample into three subsamples and find that smaller sample sizes can induce large differences in the correlation slopes. We also derive an average CO spectral line energy distribution for the entire sample and discuss the implied average molecular gas properties for these local galaxies. We further extend our sample to high-z galaxies with CO(J = 5-4) data from the literature as an example, including submillimeter galaxies (SMGs) and "normal" star-forming BzKs. BzKs have similar FIR/CO(5–4) ratios as those of local galaxies, and agreeably follow the locally-determined correlation, whereas SMG ratios fall around or slightly above the local correlation with large uncertainties. Finally, by including Galactic CO(J = 10-9) data as well as very limited high-z CO(J = 10–9) data, we verify that the CO(J = 10-9)–FIR correlation successfully extends to Galactic young stellar objects, suggesting that linear correlations are valid over 15 orders of magnitude.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Daddi, Emanuele0000-0002-3331-9590
Lu, Nanyao0000-0002-8948-1044
van der Werf, Paul0000-0001-5434-5942
Additional Information:© 2015. The American Astronomical Society. Received 2015 May 20; accepted 2015 August 2; published 2015 September 1. This work is supported by NSFC #11173059, #11390373, #11420101002, and CAS #XDB09000000. D.L. gratefully thanks T. Greve, Z. Zhang, P. Papadopoulos, S. Madden, and R. Wu for constructive discussions, and K. Okumura and B. Altieri for helpful instructions on PACS.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Natural Science Foundation of China11173059
National Natural Science Foundation of China11390373
National Natural Science Foundation of China11420101002
Chinese Academy of SciencesXDB09000000
Subject Keywords:galaxies: ISM; galaxies: starburst; infrared: ISM; ISM: molecules
Issue or Number:2
Record Number:CaltechAUTHORS:20151204-153236972
Persistent URL:
Official Citation:Daizhong Liu et al 2015 ApJ 810 L14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62628
Deposited By: Ruth Sustaita
Deposited On:08 Dec 2015 22:13
Last Modified:03 Oct 2019 09:20

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