The Gas Properties of Galaxies on and off of a Star-Forming Sequence David Schiminovich + GALEX Science Team Columbia University

Simple questions… What determines: - the star formation rate (SFR) of galaxies? - the rate of change of the SFR? Must be something about the gas…

Measuring Gas in Galaxies: Direct: HI, CO, etc. Indirect: Star Formation Schmidt-Kennicutt Law, “Photometric gas fractions” (e.g. Bell et al. 2003, Knappanan 2004, Reddy et al. 2006) Indirect: Dust Attenuation (e.g. Wang & Heckman 1996, Bell 2003, GALEX: Johnson et al. 2007, Martin et al. 2007)

Galaxy Distribution in SFR and Stellar Mass: UV-Optical Color Magnitude Distribution Wyder et al (2007) Bivariate Luminosity Function (z~0.1) GALEX Medium Imaging Survey + SDSS(sp) Wyder, Salim, Martin, Schiminovich

Interpreting the Color-Magnitude Distribution Faber et al. (2007) DEEP2 Bell et al. (2007) Combo17

UV-Optical Color Magnitude Distribution: Converting to Physical Properties Schiminovich et al. (2007) submitted Observed Distribution - 1/V max - k-corrected Intrinsic “Dust-corrected” Distribution UV,cor->SFR M r,cor -> M *

SFR/M * vs. M * Distribution ‘Red locus’: Upper limit to SFR/M * Star-forming sequence Schiminovich et al. (2007) submitted

SFR/M * vs. M * distribution derived from model star formation histories Salim et al. (2007) Identical GALEX+ SDSS(sp) Data set

SFR/M * vs. M * Distribution: Star-Forming Sequence Salim et al. (2007) Noeske et al. (2007) see also Brinchmann et al. (2004), Feulner et al. (2006)

Noeske et al (2007) AEGIS team to z~1 SFR zero-point increases vs. z SFR/M * vs. M * Distribution: Star-Forming Sequence Evolution

Properties of galaxies along blue/red sequence: Stellar Mass Surface Density

Properties of galaxies along SF sequence: Half-light radius: r 50,i

Properties of galaxies along SF sequence: SFR Surface Density:  SFR see also Hoopes et al. (2007)

Star-forming galaxies distributed around locus of constant  SFR vs. M * Evolves slowly to z~1 (e.g. Somerville et al. 2007) Same at z~1 (e.g. Noeske et al. 2007) Same at z~1 with increased intensity See also Hoopes et al. (2007) May suggest  gas ~ const vs. M * SB ‘intensity limit’ at least x100 higher

SFR/M * vs. M * Distribution: “Disk-dominated” vs. “Bulge-dominated” galaxies “Bulge-dominated” (n > 2.4) “Disk-dominated” (n < 2.4) Extends to SF sequence Schiminovich et al. (2007) submitted

SFR/M * Distribution in M * bins: Disk-dominated vs. Bulge Dominated Will high SFR bulge- dominated galaxies soon transition to the red sequence?

SFR/M * vs. M * Distribution: Flow Evolution off of the SF sequence “Green Valley” evolution Gas may provide information about `potential’ for accretion/quenching (direction) Schiminovich et al. (2007) submitted Martin et al. (2007)

E4 NUV-K=4.8 S0 NUV-K=4.2 Sa NUV-K=3.9 Sb NUV-K=2.8 Sc NUV-K=0.9 Sd NUV-K=0.4 Im NUV-K=-1 GALEX Nearby Galaxy Atlas Gil de Paz et al. (2007) 1037 galaxies (900 both FUV+NUV) m AB ~ 27.5 mag / arcsec sq. SFR/Area ~ M sun /kpc 2 Combined with M(HI) from literature (+LEDA) - Heterogeneous selection!

SFR/M * and Gas Fraction vs M * SF Sequence and Residual SF Galaxies SF Sequence: Scatter to low gas fraction NGC 7252 Quenching?

SFR/M * and Gas Fraction vs M * SF Sequence and Residual SF Galaxies Residual SF: Scatter to high gas fraction Accretion?

SFR/M * and Gas Fraction vs M * NGC 5701: Residual SF, elev. gas fraction Accretion?

SFR/M * and Gas Fraction vs M * NGC 1023: Residual SF, elev. gas fraction Accretion?

SFR/M * and Gas Fraction vs M * NGC 1291: Residual SF, elev. gas fraction Accretion? See e.g. Kauffmann et al. (2007)

Massive Galaxy Sample (log M * >10) from SDSS (z<0.05) + GALEX Green: Morganti et al. (2006)- Sauron Red: Oosterloo et al. (2007) - HIPASS ALFALFA - mostly lower M * SF sequence galaxies from SDSS

Summary and Conclusions UV-optical CMD displays widely separated blue and red sequences and “green valley”. New aspects are: Improved measurements of physical quantities Identification of ‘locus’ of SF sequence galaxies and associated scaling relations New understanding of the volume-weighted distribution and implications for evolutionary scenarios In Nearby Galaxy sample HI gas fractions correlate with SFR/M *, but with interesting scatter Gas properties of galaxies near ‘transition mass’ (log M * ~ 10.5) to moderate gas fractions (1-10%) worth investigating