The BIMA Survey of Nearby Galaxies. I. The Radial Distribution of CO Emission in Spiral Galaxies

By M. Regan, M. Thornley, T. Helfer, K. Sheth, T. Wong, S. Vogel, L. Blitz, D. Bock. 2001

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We present the first results of the Berkeley-Illinois-Maryland Association Survey of Nearby Galaxies (BIMA SONG), an imaging survey of the CO J = 1-0 emission in 44 nearby spiral galaxies at a typical resolution of 6''. BIMA SONG differs from previous high-resolution CO surveys in that (1) CO brightness was not an explicit selection criterion, (2) a larger area (200'' diameter for most galaxies) of each galaxy was imaged, and (3) fully sampled single-dish CO data (55'' resolution) were obtained for over half of the sample galaxies, so all of the CO flux is imaged in these galaxies. Here we present CO maps for a subsample of 15 BIMA SONG galaxies for which we have also obtained near-infrared or optical broadband data. The CO maps display a remarkable variety of molecular gas morphologies, and, as expected, the CO surface brightness distributions show considerably more substructure than the stellar light distributions, even when averaged over kiloparsec scales. The radial distribution of stellar light in galactic disks is generally characterized as an exponential. It is, therefore, of interest to investigate whether the molecular gas, which is the star-forming medium, has a similar distribution. Though our low-resolution single-dish radial profiles of CO emission can be described by simple exponentials, this is not true for the emission at our full 6'' resolution. The scale lengths of the CO disks are correlated with the scale lengths of the stellar disks, with a mean ratio of the scale lengths of about 1. There is, however, considerable intrinsic scatter in the correlation. We also find that (1) there is also a weak correlation between the ratio of K-band to CO luminosity and Hubble type; (2) in half of the galaxies presented here, CO emission does not peak at the location of the stellar nucleus; (3) averaged over the inner kiloparsec, the CO emission in one-half of the galaxies exhibits an excess over that expected from an exponential disk, which is similar to the excess in stellar light caused by the bulge stars; and (4) this excess CO emission may be due to an increase in the total molecular gas content in the bulge region, or alternatively, to an increase in the CO emissivity caused by the increased pressure of the bulge region.

Subfields: Astronomy and Astrophysics, Spectroscopy

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. M. Cappellari
4. Mark R. Krumholz
5. R. Somerville
6. T. Naab
7. A. Dekel
8. F. Walter

In Spectroscopy

1. Mark R. Krumholz
2. L. Blitz
3. A. Leroy
4. F. Walter
5. A. Bolatto
6. M. Heyer
7. T. Naab
8. R. Genzel

Citations in the corpus

• Cosmic evolution of the atomic and molecular gas contents of galaxies (2011, methodology): “On the other hand, the median of the relation between the exponential scale length of the H2 and HI disks predicted by the model is RH2 ≈ 0.4RHI, while the relation inferred by combining the observational results of Regan et al. (2001) and Verheijen & Sancisi (2001) isRH2 = (0.44 ± 0.12)RHI.”
• The star formation rate in disc galaxies: thresholds and dependence on gas amount (2003, methodology): “In their recent study concerning the star formation rate in galactic disks, Wong & Blitz (2002) used high resolution profiles obtained with the BIMA interferometer (Regan et al. 2001) for 7 disk galaxies.”
• SIMULATION OF THE COSMIC EVOLUTION OF ATOMIC AND MOLECULAR HYDROGEN IN GALAXIES (2009, background): “Indeed, several observational studies revealed that the stellar scale length is nearly identical to that of molecular gas (e.g. Young et al. 1995; Regan et al. 2001; Leroy et al. 2008), and hence smaller than the scale length of HI or the scale length rdisk of the total cold gas component.”
• Cloud-scale Molecular Gas Properties in 15 Nearby Galaxies (2018, background): “…known that molecular gas in the central region of disk galaxies has different properties compared to the gas in the disk (e.g., Oka et al. 2001; Regan et al. 2001; Jogee et al. 2005; Shetty et al. 2012; Kruijssen & Longmore 2013; Colombo et al. 2014a; Leroy et al. 2015; Freeman et al. 2017,…”
• The BIMA Survey of Nearby Galaxies (BIMA SONG). II. The CO Data (2002, result): “BIMA SONG was introduced in the recent study by Regan et al. (2001), hereafter Paper I, where we presented initial results for a subsample of 15 spiral galaxies.”
• THE ATOMIC-TO-MOLECULAR TRANSITION IN GALAXIES. II: H i AND H2 COLUMN DENSITIES (2008, methodology): “The H2 surface densities are inferred from CO observations taken as part of the BIMA SONG survey (Regan et al. 2001; Helfer et al. 2003), while the Hi observations are from the VLA.”
• PHIBSS: MOLECULAR GAS CONTENT AND SCALING RELATIONS IN z ∼ 1–3 MASSIVE, MAIN-SEQUENCE STAR-FORMING GALAXIES (2012, result): “Molecular gas and optical light distributions have comparable overall radial scales, in agreement with the same finding in z~0 disk galaxies (e.g. Young et al. 1995, Regan et al. 2001, Leroy et al. 2008).”
• Radial Variation of Attenuation and Star Formation in the Largest Late-Type Disks Observed with GALEX (2006, unknown): “…Pisano et al. (1998) ; 32 Puche et al. (1990) ; 33 Puche, Carignan & Wainscoat (1991) ; 34 Puche, Carignan & van Gorkom (1991) ; 35 Rand (1994) ; 36 Regan et al. (2001) ; 37 Sakamoto et al. (1997) ; 38 Sancisi & Allen (1979) ; 39 Shostak & van der Kruit (1984) ; 40 Sofue (1997) ; 43 Sorai et al.…”
• THE STAR FORMATION EFFICIENCY IN NEARBY GALAXIES: MEASURING WHERE GAS FORMS STARS EFFECTIVELY (2008, unknown): “Our CO scale lengths are taken from Leroy et al. (2008); these are ∼ 30% shorter than those of Regan et al. (2001) on average.”
• The Relationship between Gas Content and Star Formation in Molecule-rich Spiral Galaxies (2001, methodology): “In this procedure, implemented in a MIRIAD task called UVDECOR written by M. Regan, the visibility amplitudes for all datasets are scaled up by a baseline-dependent correction factor, typically∼1–1.2, based on the expected amplitude loss due to phase decorrelation (see Regan et al. 2001).”
• Molecular gas in NUclei of GAlaxies (NUGA) - IV. Gravitational torques and AGN feeding (2005, unknown): “However, observational evidence indicates that the dominant variation of XCO in the central regions of galaxies is radial (Solomon & Barrett 1991; Regan et al. 2001).”
• The ATLAS3D Project – XXVIII. Dynamically driven star formation suppression in early-type galaxies (2014, background): “As part of the BIMA-SONG survey, Regan et al. (2001) showed that molecular gas embedded in the bulges of spiral galaxies seems to emit more strongly (in the CO(1-0) line) than gasin the disc regions.”
• THE STRUCTURE OF CLASSICAL BULGES AND PSEUDOBULGES: THE LINK BETWEEN PSEUDOBULGES AND SÉRSIC INDEX (2008, background): “These similarities have been shown in the flatness of stellar population gradients (Peletier & Balcells 1996), and the similarity of CO profiles to optical light (Regan et al. 2001).”
• The Molecular Gas Distribution and Schmidt Law in M33 (2003, background): “High-resolution images of CO emission in more distant galaxies typically reveal a strong concentration of molecular gas in spiral arms (Regan et al. 2001).”
• THE CO-TO-H2 CONVERSION FACTOR AND DUST-TO-GAS RATIO ON KILOPARSEC SCALES IN NEARBY GALAXIES (2012, background): “Comparison with CO Exponential Disk Profiles Regan et al. (2001) found that approximately half of their sample of galaxies observed in the BIMA SONG survey show excess CO emission in their centers compared to the extrapolation of their best fit exponential disk profile.”
• Giant Molecular Clouds in M33. II. High-Resolution Observations (2003, methodology): “Our data reduction followed the algorithm developed for the BIMA Survey of Nearby Galaxies (Regan et al. 2001).”