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STUDYING LARGE- AND SMALL-SCALE ENVIRONMENTS OF ULTRAVIOLET LUMINOUS GALAXIES
Basu-Zych, Antara R.,Schiminovich, David,Heinis, Sebastien,Overzier, Roderik,Heckman, Tim,Zamojski, Michel,Ilbert, Olivier,Koekemoer, Anton M.,Barlow, Tom A.,Bianchi, Luciana,Conrow, Tim,Donas, Jose,F IOP Publishing 2009 The Astrophysical journal Vol.699 No.2
Thilker, David A.,Bianchi, Luciana,Schiminovich, David,Gil de Paz, Armando,Seibert, Mark,Madore, Barry F.,Wyder, Ted,Rich, R. Michael,Yi, Sukyoung,Barlow, Tom,Conrow, Tim,Forster, Karl,Friedman, Peter IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.714 No.1
<P>We have discovered recent star formation in the outermost portion ((1-4) x R(25)) of the nearby lenticular (S0) galaxy NGC 404 using Galaxy Evolution Explorer UV imaging. FUV-bright sources are strongly concentrated within the galaxy's Hi ring (formed by a merger event according to del Rio et al.), even though the average gas density is dynamically subcritical. Archival Hubble Space Telescope imaging reveals resolved upper main-sequence stars and conclusively demonstrates that the UV light originates from recent star formation activity. We present FUV, NUV radial surface brightness profiles, and integrated magnitudes for NGC 404. Within the ring, the average star formation rate (SFR) surface density (Sigma(SFR)) is similar to 2.2 x 10(-5) M(circle dot) yr(-1) kpc(-2). Of the total FUV flux, 70% comes from the H I ring which is forming stars at a rate of 2.5 x 10(-3) M(circle dot) yr(-1). The gas consumption timescale, assuming a constant SFR and no gas recycling, is several times the age of the universe. In the context of the UV-optical galaxy color-magnitude diagram, the presence of the star-forming Hi ring places NGC 404 in the green valley separating the red and blue sequences. The rejuvenated lenticular galaxy has experienced a merger-induced, disk-building excursion away from the red sequence toward bluer colors, where it may evolve quiescently or (if appropriately triggered) experience a burst capable of placing it on the blue/star-forming sequence for up to similar to 1 Gyr. The green valley galaxy population is heterogeneous, with most systems transitioning from blue to red but others evolving in the opposite sense due to acquisition of fresh gas through various channels.</P>
UV Star Formation Rates in the Local Universe
Salim, Samir,Rich, R. Michael,Charlot, Stephane,Brinchmann, Jarle,Johnson, Benjamin D.,Schiminovich, David,Seibert, Mark,Mallery, Ryan,Heckman, Timothy M.,Forster, Karl,Friedman, Peter G.,Martin, D. C IOP Publishing 2007 The Astrophysical journal, Supplement series Vol.173 No.2
CAUGHT IN THE ACT: STRONG, ACTIVE RAM PRESSURE STRIPPING IN VIRGO CLUSTER SPIRAL NGC 4330
Abramson, Anne,Kenney, Jeffrey D. P.,Crowl, Hugh H.,Chung, Aeree,van Gorkom, J. H.,Vollmer, Bernd,Schiminovich, David American Institute of Physics 2011 The Astronomical journal Vol.141 No.5
<P>We present a multi-wavelength study of NGC 4330, a highly inclined spiral galaxy in the Virgo Cluster which is a clear example of strong, ongoing intracluster medium-interstellar medium (ICM-ISM) ram pressure stripping. The H <SPAN CLASS='sml'>I</SPAN> has been removed from well within the undisturbed old stellar disk, to 50%-65% of R<SUB>25</SUB>. Multi-wavelength data (WIYN BVR-Hα, Very Large Array 21 cm H <SPAN CLASS='sml'>I</SPAN> and radio continuum, and Galaxy Evolution Explorer NUV and FUV) reveal several one-sided extraplanar features likely caused by ram pressure at an intermediate disk-wind angle. At the leading edge of the interaction, the Hα and dust extinction curve sharply out of the disk in a remarkable and distinctive 'upturn' feature that may be generally useful as a diagnostic indicator of active ram pressure. On the trailing side, the ISM is stretched out in a long tail which contains 10% of the galaxy's total H <SPAN CLASS='sml'>I</SPAN> emission, 6%-9% of its NUV-FUV emission, but only 2% of the Hα. The centroid of the H <SPAN CLASS='sml'>I</SPAN> tail is downwind of the UV/Hα tail, suggesting that the ICM wind has shifted most of the ISM downwind over the course of the past 10-300 Myr. Along the major axis, the disk is highly asymmetric in the UV, but more symmetric in Hα and H <SPAN CLASS='sml'>I</SPAN>, also implying recent changes in the distributions of gas and star formation. The UV-optical colors indicate very different star formation histories for the leading and trailing sides of the galaxy. On the leading side, a strong gradient in the UV-optical colors of the gas-stripped disk suggests that it has taken 200-400 Myr to strip the gas from a radius of >8 to 5 kpc, but on the trailing side there is no age gradient. All our data suggest a scenario in which NGC 4330 is falling into the cluster center for the first time and has experienced a significant increase in ram pressure over the last 200-400 Myr. Many of the UV-bright stars that form outside the thin disk due to ram pressure will ultimately produce stellar thick disk and halo components with characteristic morphologies and age distributions distinct from those produced by gravitational interactions.</P>
THE STAR FORMATION LAW AT LOW SURFACE DENSITY
Wyder, Ted K.,Martin, D. Christopher,Barlow, Tom A.,Foster, Karl,Friedman, Peter G.,Morrissey, Patrick,Neff, Susan G.,Neill, James D.,Schiminovich, David,Seibert, Mark,Bianchi, Luciana,Donas, Jos&eacu IOP Publishing 2009 The Astrophysical journal Vol.696 No.2