Browsing by Subject "submillimeter galaxies"
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Item Keck-I Mosfire Spectroscopy Of Compact Star-Forming Galaxies At Z Greater Than Or Similar To 2: High Velocity Dispersions In Progenitors Of Compact Quiescent Galaxies(2014-11) Barro, Guillermo; Trump, Jonathan R.; Koo, David C.; Dekel, Avishai; Kassin, Susan A.; Kocevski, Dale D.; Faber, Sandra M.; van der Wel, Arjen; Guo, Yicheng; Perez-Gonzalez, Pablo G.; Toloba, Elisa; Fang, Jerome J.; Pacifici, Camilla; Simons, Raymond; Campbell, Randy D.; Ceverino, Daniel; Finkelstein, Steven L.; Goodrich, Bob; Kassis, Marc; Koekemoer, Anton M.; Konidaris, Nicholas P.; Livermore, Rachael C.; Lyke, James E.; Mobasher, Bahram; Nayyeri, Hooshang; Peth, Michael; Primack, Joel R.; Rizzi, Luca; Somerville, Rachel S.; Wirth, Gregory D.; Zolotov, Adi; Finkelstein, Steven L.; Livermore, Rachael C.We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift 2 <= z <= 2.5 with star formation rates of SFR similar to 100M(circle dot)yr(-1) and masses of log( M/M-circle dot) similar to 10.8. Their high integrated gas velocity dispersions of sigma(int) = 230(-30)(+40)km s(-1), as measured from emission lines of Ha and [O III], and the resultant M-star-sigma(int) relation and M-star-M-dyn all match well to those of compact quiescent galaxies at z similar to 2, as measured from stellar absorption lines. Since log( M-star/M-dyn)= -0.06 +/- 0.2 dex, these compact SFGs appear to be dynamically relaxed and evolved, i.e., depleted in gas and dark matter (<13(-13)(+17)%), and present larger sint than their non-compact SFG counterparts at the same epoch. Without infusion of external gas, depletion timescales are short, less than similar to 300 Myr. This discovery adds another link to our new dynamical chain of evidence that compact SFGs at z greater than or similar to 2 are already losing gas to become the immediate progenitors of compact quiescent galaxies by z similar to 2.Item The Metallicity Dependence Of The Co -> H-2 Conversion Factor In Z >= 1 Star-Forming Galaxies(2012-02) Genzel, R.; Tacconi, L. J.; Combes, Francoise; Bolatto, A.; Neri, R.; Sternberg, Assaf; Cooper, Michael C.; Bouche, N.; Bournaud, F.; Burkert, A.; Comerford, J.; Cox, P.; Davis, M.; Schreiber, N. M. F.; Garcia-Burillo, S.; Gracia-Carpio, J.; Lutz, D.; Naab, T.; Newman, S.; Saintonge, A.; Shapiro, K.; Shapley, A.; Weiner, B.; Comerford, J.We use the first systematic samples of CO millimeter emission in z >= 1 "main-sequence" star-forming galaxies to study the metallicity dependence of the conversion factor alpha(CO), from CO line luminosity to molecular gas mass. The molecular gas depletion rate inferred from the ratio of the star formation rate (SFR) to CO luminosity, is similar to 1 Gyr(-1) for near-solar metallicity galaxies with stellar masses above M-S similar to 10(11) M-circle dot. In this regime, the depletion rate does not vary more than a factor of two to three as a function of molecular gas surface density or redshift between z similar to 0 and 2. Below M-S the depletion rate increases rapidly with decreasing metallicity. We argue that this trend is not caused by starburst events, by changes in the physical parameters of the molecular clouds, or by the impact of the fundamental-metallicity-SFR-stellar mass relation. A more probable explanation is that the conversion factor is metallicity dependent and that star formation can occur in "CO-dark" gas. The trend is also expected theoretically from the effect of enhanced photodissociation of CO by ultraviolet radiation at low metallicity. From the available z similar to 0 and z similar to 1-3 samples we constrain the slope of the log(alpha CO)-log (metallicity) relation to range between -1 and -2, fairly insensitive to the assumed slope of the gas-SFR relation. Because of the lower metallicities near the peak of the galaxy formation activity at z similar to 1-2 compared to z similar to 0, we suggest that molecular gas masses estimated from CO luminosities have to be substantially corrected upward for galaxies below M-S.Item O III Emission And Gas Kinematics In A Lyman-Alpha Blob At Z Similar To 3.1(2013-04) McLinden, Emily M.; Malhotra, Sangeeta; Rhoads, James E.; Hibon, Pascale; Weijmans, Anne-Marie; Tilvi, Vithal; McLinden, Emily M.We present spectroscopic measurements of the [O III] emission line from two subregions of strong Ly alpha emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z similar to 3.1, and the [OIII] detections are from the two Lyman break galaxies (LBGs) embedded in the blob halo. The [OIII] measurements were made with LUCIFER on the 8.4 m Large Binocular Telescope and NIRSPEC on 10 m Keck Telescope. Comparing the redshift of the [OIII] measurements to Ly alpha redshifts from SAURON allows us to take a step toward understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [OIII] and Lya redshifts that are modestly negative or consistent with 0 km s(-1) in both subregions studied (ranging from -72+/-42-+6+/-33 km s(-1)). A negative offset means Ly alpha is blueshifted with respect to [O III] a positive offset then implies Lya is redshifted with respect to [O III]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset. In addition, we present an [O III] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [OIII] upper limit from the galaxy-unassociated region of the blob is at least 1.4-2.5 times fainter than the [OIII] flux from one of the LBG-associated regions and has an [O III] to Ly alpha ratio measured at least 1.9-3.4 times smaller than the same ratio measured from one of the LBGs.Item Spectral Energy Distribution Fitting Of HETDEX Pilot Survey Ly Alpha Emitters In Cosmos And GOODS-N(2014-05) Hagen, Alex; Ciardullo, Robin; Gronwall, Caryl; Acquaviva, Viviana; Bridge, Joanna; Zeimann, Gregory R.; Blanc, Guillermo A.; Bond, Nicholas A.; Finkelstein, Steven L.; Song, Mimi; Gawiser, Eric; Fox, Derek B.; Gebhardt, Henry; Malz, A. I.; Schneider, Donald P.; Drory, Niv; Gebhardt, Karl; Hill, Gary J.; Drory, Niv; Gebhardt, Karl; Hill, Gary J.We use broadband photometry extending from the rest-frame UV to the near-IR to fit the individual spectral energy distributions of 63 bright (L(Ly alpha) > 10(43) erg s(-1)) Ly alpha emitting galaxies (LAEs) in the redshift range 1.9 < z < 3.6. We find that these LAEs are quite heterogeneous, with stellar masses that span over three orders of magnitude, from 7.5 < log M/M-circle dot < 10.5. Moreover, although most LAEs have small amounts of extinction, some high-mass objects have stellar reddenings as large as E(B - V) similar to 0.4. Interestingly, in dusty objects the optical depths for Ly alpha and the UV continuum are always similar, indicating that Ly alpha photons are not undergoing many scatters before escaping their galaxy. In contrast, the ratio of optical depths in low-reddening systems can vary widely, illustrating the diverse nature of the systems. Finally, we show that in the star-formation-rate-log-mass diagram, our LAEs fall above the "main-sequence" defined by z similar to 3 continuum selected star-forming galaxies. In this respect, they are similar to submillimeter-selected galaxies, although most LAEs have much lower mass.