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Suppression of star formation in early-type galaxies by feedback from supermassive black holes
Schawinski, Kevin,Khochfar, Sadegh,Kaviraj, Sugata,Yi, Sukyoung K.,Boselli, Alessandro,Barlow, Tom,Conrow, Tim,Forster, Karl,Friedman, Peter G.,Martin, D. Chris,Morrissey, Patrick,Neff, Susan,Schimino Nature Publishing Group 2006 Nature Vol.442 No.7105
Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of ‘feedback’ in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.
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>