HERACLES: THE HERA CO LINE EXTRAGALACTIC SURVEY

By A. Leroy, F. Walter, F. Bigiel, A. Usero, A. Weiss, E. Brinks, W. D. de Blok, Robert C. Kennicutt Jr., K. Schuster, C. Kramer and 2 more. 2009

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We present the Heterodyne Receiver Array CO Line Extragalactic Survey, an atlas of CO emission from 18 nearby galaxies that are also part of The H i Nearby Galaxy Survey and the Spitzer Infrared Nearby Galaxies Survey. We used the HERA multipixel receiver on the IRAM 30-m telescope to map the CO J = 2 → 1 line over the full optical disk (defined by the isophotal radius r25) of each target, at 13″ angular resolution and 2.6 km s−1 velocity resolution. Here we describe the observations and reduction of the data and show channel maps, azimuthally averaged profiles, integrated intensity maps, and peak intensity maps. The implied H2 masses range from 7 × 106 to 6 × 109M☉, with four low metallicity dwarf irregular galaxies yielding only upper limits. In the cases where CO is detected, the integrated H2-to-H i ratios range from 0.02 to 1.13 and H2-to-stellar mass ratios from 0.01 to 0.25. Exponential scale lengths of the CO emission for our targets are in the range 0.8–3.2 kpc, or 0.2 ± 0.05r25. The intensity-weighted mean velocity of CO matches that of H i very well, with a 1σ scatter of only 6 km s−1. The CO J = 2 → 1/J = 1 → 0 line ratio varies over a range similar to that found in the Milky Way and other nearby galaxies, ∼0.6–1.0, with higher values found in the centers of galaxies. The typical line ratio, ∼0.8, could be produced by optically thick gas with an excitation temperature of ∼10 K.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

• REGULARITY UNDERLYING COMPLEXITY: A REDSHIFT-INDEPENDENT DESCRIPTION OF THE CONTINUOUS VARIATION OF GALAXY-SCALE MOLECULAR GAS PROPERTIES IN THE MASS-STAR FORMATION RATE PLANE (2013, unknown): “Normal Galaxies: Low-redshift CO-detections The HERACLES survey (Leroy et al. 2008, 2009, 2013) targeted the CO(J=2→1) transition in nearby (D. 15Mpc) THINGS galaxies (Walter et al. 2008) with the IRAM 30m single-dish telescope.”
• Star formation in semi-analytic galaxy formation models with multiphase gas (2015, background): “…and multi-phase (Hi and H2) gas in reasonably large samples of nearby galaxies, e.g. from the THINGS (The HI nearby galaxy survey; Walter et al. 2008) combined with BIMA SONG (BIMA survey of Nearby Galaxies; Helfer et al. 2003) and HERACLES (HERA COLine Extragalactic Survey; Leroy et al. 2009).”
• PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions (2017, background): “In the local Universe optical continuum and CO sizes of main sequence galaxies correlate well empirically (e.g. Young & Scoville 1991, Leroy et al 2009, 2013), and the first spatially resolved CO sizes in large z~1-2 disks seem to support this assumption as well (Tacconi et al. 2013; M. Lippa et…”
• A UNIVERSAL, LOCAL STAR FORMATION LAW IN GALACTIC CLOUDS, NEARBY GALAXIES, HIGH-REDSHIFT DISKS, AND STARBURSTS (2011, unknown): “…Group Galaxies Our data set for resolved observations of Local Group galaxies is taken from The H i Nearby Galaxy Survey (THINGS; Walter et al. 2008; Bigiel et al. 2008; Leroy et al. 2008), supplemented with CO measurements from the HERA CO Line Extrgalactic Survey (HERACLES; Leroy et al. 2009).”
• CO excitation of normal star forming galaxies out to $z=1.5$ as regulated by the properties of their interstellar medium (2014, methodology): “We also use measurements from HERACLES (Leroy et al 2009) of CO[2-1].”
• THE ARECIBO LEGACY FAST ALFA SURVEY: THE GALAXY POPULATION DETECTED BY ALFALFA (2012, background): “For example, the HI Nearby Galaxy Survey (THINGS; Walter et al. 2008) and the HERA CO Line Extragalactic Survey (HERACLES; Leroy et al. 2009) provide measurements of the surface densities of total gas, atomic and molecular gas, and SFR in ∼kpc-sized regions within a number of nearby galaxies.”
• A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION (2012, methodology): “The cyan diamonds rep- resent 14 galaxies from the HERACLES survey (Leroy et al. 2009) with H2 masses measured from interferometric CO line observations (using a fixed αCO conversion factor).”
• EVIDENCE FOR A CLUMPY, ROTATING GAS DISK IN A SUBMILLIMETER GALAXY AT z = 4 (2012, methodology): “Moment Maps Given the high–quality of the data, we created moment maps by following the typical approach used for HI and CO observations of nearby galaxies (e.g. Walter et al. 2008; Leroy et al. 2009).”
• Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range (2013, background): “First, detection of CO in low-metallicity galaxies is challenging: sensitivity has limited CO detections to galaxies with 12 + log(O/H) & 8.0 (e.g., Leroy et al. 2009; Schruba et al. 2012).”
• The lifecycle of molecular clouds in nearby star-forming disc galaxies (2019, background): “The CO (J=1-0) transition [denoted as CO(1-0) in the following] and the CO (J=2-1) transition [denoted as CO(2-1) in the following] are commonly used to trace molecular gas (e.g. Schuster et al. 2007; Leroy et al. 2009; Bolatto et al. 2013; Sandstrom et al. 2013).”
• Star Formation in the Milky Way and Nearby Galaxies (2012, background): “These surveys in turn have led to large spinoff surveys in H I (e.g., THINGS, Walter et al. 2008; FIGGS, Begum et al. 2008; Local Volume H I Survey; Koribalski 2010; LITTLE THINGS, Hunter et al. 2007) and in CO (e.g., BIMA-SONG, Helfer et al. 2003; IRAM HERACLES, Leroy et al. 2009; JCMT NGLS, Wilson”
• Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks (2009, background): “We also point out that some galaxies reveal a noticeable HI depletion in their central regions where the gas is mostly molecular (Leroy et al. 2008, 2009).”
• A MOLECULAR STAR FORMATION LAW IN THE ATOMIC-GAS-DOMINATED REGIME IN NEARBY GALAXIES (2011, methodology): “APPENDIX Here we present the radial profiles of CO, H i, FUV, Hα, and IR at 24 µm and 70 µm used to generate the plots in this paper.”
• The ATLAS3D project - XIV. The extent and kinematics of the molecular gas in early-type galaxies (2012, methodology): “Various authors (e.g. Young & Scoville 1982; Regan et al. 2001; Leroy et al. 2009) have studied the correspondence between the radial profile of the molecular gas and that of the stars in spiral galaxies.”
• Dusty Star Forming Galaxies at High Redshift (2014, methodology): “Utilizing data from the THINGS, HERACLES, and BIMA SONG surveys (Walter et al., 2005; Leroy et al., 2009; Helfer et al., 2003), Bigiel et al. (2008) investigated the resolved star formation law in nearby galaxies.”
• THE CO-TO-H2 CONVERSION FACTOR AND DUST-TO-GAS RATIO ON KILOPARSEC SCALES IN NEARBY GALAXIES (2012, methodology): “For this study, we make use of CO J=(2− 1) observations from the large program HERACLES on the IRAM 30m (Leroy et al. 2009a).”