J/ApJ/734/L22 ACS Nearby Galaxy Survey Treasury (Williams+, 2011) ================================================================================ The history of star formation in galaxy disks in the local volume as measured by the Advanced Camera for Surveys Nearby Galaxy Survey Treasury. Williams B.F., Dalcanton J.J., Johnson L.C., Weisz D.R., Seth A.C., Dolphin A., Gilbert K.M., Skillman E., Rosema K., Gogarten S.M., Holtzman J., de Jong R.S. =2011ApJ...734L..22W ================================================================================ ADC_Keywords: Galaxies, nearby ; Photometry, HST Keywords: cosmology: observations - galaxies: evolution - galaxies: stellar content Abstract: We present a measurement of the age distribution of stars residing in spiral disks and dwarf galaxies. We derive a complete star formation history of the ~140Mpc^3^ covered by the volume-limited sample of galaxies in the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST). The total star formation rate density history ({rho}_SFR_(t)) is dominated by the large spirals in the volume, although the sample consists mainly of dwarf galaxies. Our {rho}_SFR_(t) shows a factor of ~3 drop at z~2, in approximate agreement with results from other measurement techniques. While our results show that the overall {rho}_SFR_(t) has decreased since z~1, the measured rates during this epoch are higher than those obtained from other measurement techniques. This enhanced recent star formation rate appears to be largely due to an increase in the fraction of star formation contained in low-mass disks at recent times. Finally, our results indicate that despite the differences at recent times, the epoch of formation of ~50% of the stellar mass in dwarf galaxies was similar to that of ~50% of the stellar mass in large spiral galaxies (z>~2), despite the observed galaxy-to-galaxy diversity among the dwarfs. Description: All of the data for this study were analyzed through the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST; GO-10915) and ACS Nearby Galaxies: Reduce, Reuse, Recycle (ANGRRR; AR-10945) programs. Our full sample is detailed in Table 1 and in Dalcanton et al. (2009ApJS..183...67D). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 76 224 Data used for star formation history determination -------------------------------------------------------------------------------- See also: B/hst : HST Archived Exposures Catalog (STScI, 2007) J/AJ/127/2031 : Catalog of neighboring galaxies (Karachentsev+, 2004) J/AJ/127/2002 : Star Formation Rate of NFGS galaxies (Kewley+, 2004) http://www.nearbygalaxies.org/ : ANGST home page http://archive.stsci.edu/prepds/angst/ : ANGST archive Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 13 A13 --- Galaxy Galaxy name 15- 19 I5 --- PID [5898/11986] Proposal ID. number of data used 21- 39 A19 --- Target Target name of dataset used 41- 45 A5 --- Cam Camera of dataset used; WFPC2 or ACS 47- 51 A5 --- Filt Broadband Filter (F435W, F475W, F555W, F606W or F814W) 53- 57 I5 s tExp Total exposure time of data used 59- 64 I6 --- Nstars [325/442068] Number of stars in the photometry catalog 66- 70 F5.2 mag m50 [24.46/29.69] Apparent magnitude of the 50% completeness limit 72- 76 F5.2 mag M50 Absolute magnitude of the 50% completeness limit -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 27-Nov-2012