The CARMA Survey Toward Infrared-bright Nearby Galaxies (STING)

The CARMA STING is an extragalactic CO survey that targets 27 galaxy disks from a sample designed to span a significant range of star-formation activities, stellar masses, specific star-formation rates (SSFR), and galaxy morphologies. The sample consists of FIR-bright galaxies with a wealth of existing ancillary data (Table 1), selected to fully span the SDSS blue sequence of active star-forming galaxies. The STING will take advantage of the strengths of CARMA --- its unique combination of collecting area, field of view, and image fidelity --- to deliver excellent images of galactic disks. Unlike previous interferometric surveys, the STING is designed to image these disks out to one-quarter to one-half of their optical radii (R25), thus probing a new and critically important domain by beginning to sample the transition from molecule-dominated to the atomic-dominated galactic regions. This project will take 3 to 4 semesters to complete. The picture on the right shows a collage of the publicly available Spitzer data (3.6, 8, and 24 um in blue, green, and red respectively) for 26 of the 27 STING galaxies.

The missing datum to put together a complete picture of galaxy evolution is the behavior of the gas reservoir. Characterizing the mechanisms by which atomic gas turns into molecular gas and ultimately into stars on galactic scales is a crucial step to understand the shaping of galaxies. The CARMA STING brings together a team from eight institutions with the goal of efficiently and systematically imaging CO in galaxies, and does so in a manner designed to maximize the impact and legacy value of the observations.

 

 

Links

Original proposal
First semester proposal
Second semester proposal
Third semester proposal
Fourth semester proposal
Fifth semester proposal
Preliminary maps as sources are observed
MIRIAD data reduction pipeline (due to Tony Wong)
Data reduction in progress (private repository)

Management. The following tasks will be pursued by the team of co-Is: Bolatto, with help from Wong, will coordinate the observations and write the scripts. Wong, with help from Bolatto, Vogel, Leroy, and Rosolowsky will lead the effort of producing mm-wave cubes from the CARMA observations. Wong and Vogel will also devote a substantial effort to further analysis of the SONG data and improvement of its data products. Bolatto and Wong will set up a website for the distribution of the STING data. Calzetti will lead the effort of producing Spitzer/Herschel images and spectra. Calzetti will also head the single-dish LMT observations. Rosolowsky will pursue JCMT observations and combine them with CARMA, both for heterodyne and SCUBA2. Walter, Bigiel, and Leroy will lead the effort of pursuing IRAM 30m/APEX observations. Ott, with help from Bigiel, Blitz, Walter, and Wong will be in charge of producing the necessary VLA radio continuum and HI cubes from archival data. West will lead the SDSS and GALEX photometry effort. Ancillary optical observations, when necessary, will be pursued by Walter, Vogel, Blitz, and Bolatto using their institutional access to Calar Alto, KPNO, and Keck/Lick. Blitz will pursue ancillary HI observations of the extended galaxy envelopes with the ATA.

All co-Is and their postdocs and students are invited to participate in all projects, but authorship in publications will be determined on the basis of their individual contributions to the paper by the lead author and the PI. It is expected that these observations will be used in several Ph.D. theses, with the student as the lead author. The following people agree to take the lead on the different science studies that will take place using the STING and ancillary data sets, with the coordination and arbitration of the PI. Wong and Walter will lead the investigations of the FIR-RC correlation and its relation to the CO distribution and SFR. Blitz will head the study of the transport of gas from the outer into the inner disk, and its relation to GMC formation. Leroy, Rosolowsky, and Bigiel will lead the studies of the different SFR prescriptions. Bolatto and Calzetti will lead the investigations of the relation between the molecular gas and the midIR/FIR emission, the cooling of the gas, and the dust-to-gas ratio and dust properties. Bolatto and Wong will lead the investigation of the molecular, baryonic, and dark mass profiles of these galaxies, with the participation of Wong's thesis student Kijeong Yim. Ott will lead the investigations of the large scale triggering of molecular cloud formation and the impact from stars on the structure and energetics of GMCs. West will lead the joint analysis of the stellar populations from 2D UV-optical-NIR photometry with the gas distribution.


DSS images for 25 of the 27 targets of the STING (NGC~1569 and NGC 6951 excepted, to allow the display in a reasonable size grid). Each panel shows a 5' by 5' patch of the sky. The red solid line indicates the mosaic coverage in each case. The dashed blue line indicates the approximate location of the 25th magnitude isophote.

The CARMA STING observations are designed to go out to at least 0.25R25, and to 0.5R25 when possible, in order to image the transition from the molecular to the atomic-dominated regime. Reaching that far out in the disk is crucial to test the different SFR prescriptions, a key goal of this survey.


Sampling of the blue sequence of galaxies using the RBGS. The gray scale shows SDSS results for SSFR vs. Galaxy Mass (from Salim et al. 2007). The dashed line shows the locus of SFR = 1 Msun/yr. The horizontal branch corresponds to the sequence of ``blue and active'' star-forming galaxies. The vertical branch corresponds to the sequence of ``red and dead'' galaxies. The right panel shows the IRAS RBGS within 45 Mpc, and the targets of the SONG and STING surveys.

The CARMA STING uniformly covers the blue sequence and samples considerably higher SSFRs than SONG.


sample histograms

Histograms contrasting the distribution of several parameters for the STING and SONG samples. The panels indicate the distributions of: a) morphological types from LEDA. b) Spatial resolution on source. c) Log of the fraction of the source area (measured by D25) covered. d) Stellar mass, M*, as measured by K-band light. e) Log of SFR. f) Log of specific SFR, or the inverse time to form M* at current SFR.

The CARMA STING is designed to uniformly sample the stellar mass range of 109 to 3 × 1011 Msun, probing a wider range of SFRs, SSFRs, FIR luminosities, and morphologies than SONG. The STING is also designed to cover a larger fraction of galaxy disks than SONG (median of 30% versus 6%), with no loss of spatial resolution and a factor of three better sensitivity (~18 vs. ~60 mJy/beam).


CO mosaic

Status of observations as of July 2009. These galaxies are complete or have a good degree of completion. Additionally NGC 1156 has been observed (undetected). We show the CO integrated intensity contours overlaid on the DSS optical images. The white dotted ellipse denotes the 0.25 R25 region in each galaxy. The 19 pointing mosaics of the interferometer illuminate the inner 2'. The tickmarks are spaced 10" appart (not all panels are the same size). The synthesized beam is indicated in the lower left corner of each panel (typical size is ~3.5").