J/ApJ/799/159 Globular cluster populations in S4G galaxies (Zaritsky+, 2015) ================================================================================ Globular cluster populations: first results from S^4^G early-type galaxies. Zaritsky D., Aravena M., Athanassoula E., Bosma A., Comeron S., Elmegreen B.G., Erroz-Ferrer S., Gadotti D.A., Hinz J.L., Ho L.C., Holwerda B., Knapen J.H., Laine J., Laurikainen E., Munoz-Mateos J.C., Salo H., Sheth K. =2015ApJ...799..159Z ================================================================================ ADC_Keywords: Galaxies, IR ; Clusters, globular Keywords: galaxies: evolution; galaxies: formation; galaxies: star clusters: general; galaxies: stellar content Abstract: Using 3.6{mu}m images of 97 early-type galaxies, we develop and verify methodology to measure globular cluster populations from the S^4^G survey images. We find that (1) the ratio, T_N_, of the number of clusters, N_CL_, to parent galaxy stellar mass, M_*_, rises weakly with M_*_ for early-type galaxies with M_*_>10^10^M_{sun}_ when we calculate galaxy masses using a universal stellar initial mass function (IMF) but that the dependence of T_N_ on M_*_ is removed entirely once we correct for the recently uncovered systematic variation of IMF with M_*_; and (2) for M_*_<10^10^M_{sun}_, there is no trend between N_CL_ and M_*_, the scatter in T_N_is significantly larger (approaching two orders of magnitude), and there is evidence to support a previous, independent suggestion of two families of galaxies. The behavior of N_CL_ in the lower-mass systems is more difficult to measure because these systems are inherently cluster-poor, but our results may add to previous evidence that large variations in cluster formation and destruction efficiencies are to be found among low-mass galaxies. The average fraction of stellar mass in clusters is ~0.0014 for M_*_>10^10^M_{sun}_ and can be as large as ~0.02 for less massive galaxies. These are the first results from the S^4^G sample of galaxies and will be enhanced by the sample of early-type galaxies now being added to S^4^G and complemented by the study of later-type galaxies within S^4^G. Description: The parent sample for this study is the S4G sample, which currently consists of 2352 galaxies selected as described by Sheth et al. (2010, J/PASP/122/1397). We observed these galaxies using the Spitzer Space Telescope and its Infrared Array Camera. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 82 97 Globular cluster population properties -------------------------------------------------------------------------------- See also: J/ApJS/217/32 : S4G galaxy morphologies in the CVRHS system (Buta+, 2015) J/MNRAS/444/3015 : Morphologies of S4G galaxies (Laine+, 2014) J/MNRAS/441/1992 : Galaxies with disc breaks in S4G and NIRS0S (Laine+, 2014) J/A+A/569/A91 : Optical imaging for S4G (Knapen+, 2014) J/AJ/147/134 : Tully-Fisher relation for S^4^G galaxies (Zaritsky+, 2014) J/ApJ/772/135 : 3.6um surface brightness from S4G (Zaritsky+, 2013) J/ApJ/772/82 : A catalog of globular cluster systems (Harris+, 2013) J/MNRAS/428/389 : SLUGGS globular clusters in early-type gal. (Pota+, 2013) J/AJ/143/87 : Massive M31 globular clusters with IRAC (Barmby+, 2012) J/ApJS/197/33 : The M87 globular cluster system (Strader+, 2011) J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010) J/AJ/139/1871 : Kinematics of globulars in NGC 5128 (Woodley+, 2010) J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009) J/MNRAS/389/1150 : Spitzer photom. of globulars in 2 galaxies (Spitler+, 2008) J/ApJ/681/197 : ACS Virgo Cluster Survey. XV (Peng+, 2008) J/MNRAS/385/361 : BVRcIc phot. of NGC 821 globular clusters (Spitler+, 2008) J/AJ/132/2268 : SAGE calibration stars (Meixner+, 2006) J/A+A/433/43 : C-T1 phot. of NGC 4636 globular clusters (Dirsch+, 2005) J/AJ/105/1762 : Globular clusters around NGC 1399 (Ostrov+ 1993) http://irsa.ipac.caltech.edu/data/SPITZER/S4G/ : S4G home page on NASA/IRSA Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Galaxy name 12- 16 F5.2 mag DM [30.2/32.4] Galaxy distance modulus 18- 19 I2 --- TT [-5/1] Galaxy T-Type of Buta et al. 2015 (J/ApJS/217/32) 21- 26 F6.1 mag [3.6] [7.9/15.2]?=-999 Spitzer/IRAC 3.6 micron AB magnitude (1) 28- 33 F6.1 mag [4.5] [8.4/15.7]?=-999 Spitzer/IRAC 4.5 microns AB magnitude (1) 35- 38 I4 --- N50 [2/2698] Number of clusters within 50kpc (2) 40- 46 F7.2 GMsun-1 TN [0.05/142]?=-999.99 Specific frequency T_N_ of globular clusters per 10^9^M_{sun}_ (3) 48- 54 F7.2 GMsun-1 e_TN ?=-999.99 Lower uncertainty on TN (3) 56- 62 F7.2 GMsun-1 E_TN ?=-999.99 Upper uncertainty on TN (3) 64- 68 F5.2 [pc-2] Back Logarithm of background level (4) 70- 74 F5.2 --- a Cluster radial profile fitting parameter (5) 76- 80 F5.2 --- b Cluster radial profile fitting parameter (5) 82- 82 I1 --- Q [0/1] Quality flag; 1=good, 0=poor -------------------------------------------------------------------------------- Note (1): Of the galaxies as measured by Munoz-Mateos et al. (2015arXiv150503534M). -999.0 if unavailable from S4G. Note (2): Derived from model fit of fixed power-law slope within 50 kpc of the galaxy. Intended to represent total number of clusters. Note (3): Specific frequency relative to the galaxy's stellar mass (T_N_), corresponding to N50 in units of number per 10^9^M_{sun} (as introduced by Zepf & Ashman 1993MNRAS.264..611Z). See section 2.2. Note (4): Clusters per projected area. Note (5): projected density = a*r^b^. -------------------------------------------------------------------------------- History: From electronic version of the journal References: Zaritsky et al. Paper II. 2016ApJ...818...99Z Cat. J/ApJ/818/99 ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 17-Jun-2015