Browsing by Author "Stefanon, Mauro"

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    Extending the evolution of the stellar mass-size relation at z ≤ 2 to low stellar mass galaxies from HFF and CANDELS
    (2021) Nedkova, Kalina, V; Haussler, Boris; Marchesini, Danilo; Dimauro, Paola; Brammer, Gabriel; Eigenthaler, Paul; Feinstein, Adina D.; Ferguson, Henry C.; Huertas-Company, Marc; Johnston, Evelyn J.; Kado-Fong, Erin; Kartaltepe, Jeyhan S.; Labbe, Ivo; Lange-Vagle, Daniel; Martis, Nicholas S.; McGrath, Elizabeth J.; Muzzin, Adam; Oesch, Pascal; Ordenes-Briceno, Yasna; Puzia, Thomas; Shipley, Heath, V; Simmons, Brooke D.; Skelton, Rosalind E.; Stefanon, Mauro; van der Wel, Arjen; Whitaker, Katherine E.
    We reliably extend the stellar mass-size relation over 0.2 <= z <= 2 to low stellar mass galaxies by combining the depth of Hubble Frontier Fields with the large volume covered by CANDELS. Galaxies are simultaneously modelled in multiple bands using the tools developed by the MegaMorph project, allowing robust size (i.e. half-light radius) estimates even for small, faint, and high redshift galaxies. We show that above 10(7) M-circle dot, star-forming galaxies are well represented by a single power law on the mass-size plane over our entire redshift range. Conversely, the stellar mass-size relation is steep for quiescent galaxies with stellar masses >= 10(10.3)M(circle dot) and flattens at lower masses, regardless of whether quiescence is selected based on star-formation activity, rest-frame colours, or structural characteristics. This flattening occurs at sizes of similar to 1 kpc at z <= 1. As a result, a double power law is preferred for the stellar mass-size relation of quiescent galaxies, at least above 10(7)M(circle dot). We find no strong redshift dependence in the slope of the relation of star-forming galaxies as well as of high mass quiescent galaxies. We also show that star-forming galaxies with stellar masses >= 10(9.5)M(circle dot) and quiescent galaxies with stellar masses >= 10(10.3)M(circle dot) have undergone significant size growth since z similar to 2, as expected; however, low mass galaxies have not. Finally, we supplement our data with predominantly quiescent dwarf galaxies from the core of the Fornax cluster, showing that the stellar mass-size relation is continuous below 10(7)M(circle dot), but a more complicated functional form is necessary to describe the relation.
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    Measuring the Average Molecular Gas Content of Star-forming Galaxies at z=3-4
    (2021) Boogaard, Leindert A.; Bouwens, Rychard J.; Riechers, Dominik; van der Werf, Paul; Bacon, Roland; Matthee, Jorryt; Stefanon, Mauro; Feltre, Anna; Maseda, Michael; Inami, Hanae; Aravena, Manuel; Brinchmann, Jarle; Carilli, Chris; Contini, Thierry; Decarli, Roberto; Gonzalez-Lopez, Jorge; Nanayakkara, Themiya; Walter, Fabian
    We study the molecular gas content of 24 star-forming galaxies at z = 3-4, with a median stellar mass of 10(9.1) M-circle dot, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Ly alpha lambda 1216 emission and H (F160W)-band magnitude, the galaxies show an average < EWLy alpha 0 > approximate to 20 angstrom, below the typical selection threshold for Ly alpha emitters (EWLy alpha 0 > 25 angstrom), and a rest-frame UV spectrum similar to Lyman-break galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Ly alpha by = 346 km s(-1), with a 100 to 600 km s(-1) range. Stacking (CO)-C-12 J = 4 -> 3 and [C I]P-3(1) -> P-3(0) (and higher-J CO lines) from the ALMA Spectroscopic Survey of the HUDF, we determine 3 sigma upper limits on the line luminosities of 4.0 x 10(8) K km s(-1)pc(2) and 5.6 x 10(8) K km s(-1)pc(2), respectively (for a 300 km s(-1) line width). Stacking the 1.2 mm and 3 mm dust-continuum flux densities, we find a 3 sigma upper limits of 9 mu Jy and 1.2 mu Jy, respectively. The inferred gas fractions, under the assumption of a "Galactic" CO-to-H-2 conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher alpha(CO) >= 10 and delta(GDR) >= 1200, consistent with the subsolar metallicity estimated for these galaxies (12 + log(O/H) approximate to 7.8 +/- 0.2). The low metallicity of z >= 3 star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [C II].