TheSpitzerSurvey of Stellar Structure in Galaxies ( S 4 G )

• Published in: Publications of the Astronomical Society of the Pacific 2010-12, Vol.122 (898), p.1397-1414
• Main Authors: Sheth, Kartik, Regan, Michael, Hinz, Joannah L., de Paz, Armando Gil, Menéndez-Delmestre, Karín, Muñoz-Mateos, Juan-Carlos, Seibert, Mark, Kim, Taehyun, Laurikainen, Eija, Salo, Heikki, Gadotti, Dimitri A., Laine, Jarkko, Mizusawa, Trisha, Armus, Lee, Athanassoula, E., Bosma, Albert, Buta, Ronald J., Capak, Peter, Jarrett, Thomas H., Elmegreen, Debra M., Elmegreen, Bruce G., Knapen, Johan H., Koda, Jin, Helou, George, Ho, Luis C., Madore, Barry F., Masters, Karen L., Mobasher, Bahram, Ogle, Patrick, Peng, Chien Y., Schinnerer, Eva, Surace, Jason A., Zaritsky, Dennis, Comerón, Sébastien, de Swardt, Bonita, Meidt, Sharon E., Kasliwal, Mansi, Aravena, Manuel
• Format: Article
• Language: eng ; jpn
• ISSN: 0004-6280; 1538-3873
• DOI: 10.1086/657638

TheSpitzerSurvey of Stellar Structure in Galaxies ( S 4 G ) is an Exploration Science Legacy Program approved for theSpitzerpost–cryogenic mission. It is a volume-, magnitude-, and size-limited ( d  30° | b | > 30 ° , m Bcorr  1′ D 25 > 1 ′ ) survey of 2331 galaxies using the Infrared Array Camera (IRAC) at 3.6 and 4.5 μm. Each galaxy is observed for 240 s and mapped to≥1.5 × D 25 ≥ 1.5 × D 25 . The final mosaicked images have a typical 1σ rms noise level of 0.0072 and0.0093 MJy sr-1 0.0093     MJy   sr - 1 at 3.6 and 4.5 μm, respectively. Our azimuthally averaged surface brightness profile typically traces isophotes atμ3.6μm(AB)(1σ) ∼ 27 mag arcsec-2 μ 3.6 μ m ( AB ) ( 1 σ ) ∼ 27     mag   arcsec - 2 , equivalent to a stellar mass surface density of∼1 M ⊙pc-2 ∼ 1     M ⊙ pc - 2 . S 4 G thus provides an unprecedented data set for the study of the distribution of mass and stellar structures in the local universe. This large, unbiased, and extremely deep sample of all Hubble types from dwarfs to spirals to ellipticals will allow for detailed structural studies, not only as a function of stellar mass, but also as a function of the local environment. The data from this survey will serve as a vital testbed for cosmological simulations predicting the stellar mass properties of present-day galaxies. This article introduces the survey and describes the sample selection, the significance of the 3.6 and 4.5 μm bands for this study, and the data collection and survey strategies. We describe the S 4 G data analysis pipeline and present measurements for a first set of galaxies, observed in both the cryogenic and warm mission phases ofSpitzer. For every galaxy we tabulate the galaxy diameter, position angle, axial ratio, inclination atμ3.6μm(AB) = 25.5 μ 3.6 μ m ( AB ) = 25.5 , and26.5 mag arcsec-2 26.5     mag   arcsec - 2 (equivalent to≈μB(AB) = 27.2 ≈ μ B ( AB ) = 27.2 and28.2 mag arcsec-2 28.2     mag   arcsec - 2 , respectively). These measurements will form the initial S 4 G catalog of galaxy properties. We also measure the total magnitude and the azimuthally averaged radial profiles of ellipticity, position angle, surface brightness, and color. Finally, using the galaxy-fitting code GALFIT, we deconstruct each galaxy into its main constituent stellar components: the bulge/spheroid, disk, bar, and nuclear point source, where necessary. Together, these data products will provide a comprehensive and de