Browsing by Author "Walter, Fabian"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    ALMA OBSERVATION OF 158 mu m [C II] LINE AND DUST CONTINUUM OF A Z=7 NORMALLY STAR-FORMING GALAXY IN THE EPOCH OF REIONIZATION
    (2014) Ota, Kazuaki; Walter, Fabian; Ohta, Kouji; Hatsukade, Bunyo; Carilli, Chris L.; Da Cunha, Elisabete; González López, Jorge; Decarli, Roberto; Hodge, Jacqueline A.; Nagai, Hiroshi
  • Thumbnail Image
    Item
    ALMA spectroscopic Survey in the Hubble Ultra Deep Field : The Infrared Excess of UV-selected z=2-10 galaxies as a function of UV-continuum Slope and Stellar Mass
    (2016) Bouwens, Rychard J.; Aravena, Manuel; Decarli, Roberto; Walter, Fabian; Cunha, Elisabete da; Labbé, Ivo; Bauer, Franz Erik; Bertoldi, Frank; Carilli, Chris; Chapman, Scott; Daddi, Emanuele; Hodge, Jacqueline; Ivison, Rob J.; Karim, Alex; Le Fevre, Olivier; Magnelli, Benjamin; Ota, Kazuaki; Riechers, Dominik; Smail, Ian R.; Werf, Paul van der; Weiss, Axel; Cox, Pierre; Elbaz, David; Gonzalez-Lopez, Jorge; Infante Lira, Leopoldo; Oesch, Pascal; Wagg, Jeff; Wilkins, Steve
  • Thumbnail Image
    Item
    ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxies
    (2016) Decarli, Roberto; Walter, Fabian; Aravena, Manuela; Carilli, Chris; Bouwens, Rychard; Da Cunha, Elisabete; Daddi, Emanuele; Bauer, Franz Erik; González López, Jorge
  • No Thumbnail Available
    Item
    Kiloparsec-scale Imaging of the CO(1-0)-traced Cold Molecular Gas Reservoir in a z ∼ 3.4 Submillimeter Galaxy
    (2022) Castillo, Marta Frias; Rybak, Matus; Hodge, Jacqueline; van der Werf, Paul; Riechers, Dominik A.; Vieira, Daniel; Rivera, Gabriela Calistro; Martinez-Ramirez, Laura N.; Walter, Fabian; de Blok, Erwin; Narayanan, Desika; Wagg, Jeff
    We present a high-resolution study of the cold molecular gas as traced by CO(1-0) in the unlensed z similar to 3.4 submillimeter galaxy SMM J13120+4242, using multiconfiguration observations with the Karl G. Jansky Very Large Array (JVLA). The gas reservoir, imaged on 0 ''.39 (similar to 3 kpc) scales, is resolved into two components separated by similar to 11 kpc with a total extent of 16 +/- 3 kpc. Despite the large spatial extent of the reservoir, the observations show a CO(1-0) FWHM linewidth of only 267 +/- 64 km s(-1). We derive a revised line luminosity of LCO(1-0)' = (10 +/- 3) x 10(10) K km s(-1) pc(2) and a molecular gas mass of M-gas = (13 +/- 3)x 10(10) (alpha(CO)/1) M-circle dot. Despite the presence of a velocity gradient (consistent with previous resolved CO(6-5) imaging), the CO(1-0) imaging shows evidence for significant turbulent motions that are preventing the gas from fully settling into a disk. The system likely represents a merger in an advanced stage. Although the dynamical mass is highly uncertain, we use it to place an upper limit on the CO-to-H-2 mass conversion factor a alpha(CO) of 1.4. We revisit the SED fitting, finding that this galaxy lies on the very massive end of the main sequence at z = 3.4. Based on the low gas fraction, short gas depletion time, and evidence for a central AGN, we propose that SMM J13120 is in a rapid transitional phase between a merger-driven starburst and an unobscured quasar. The case of SMM J13120 highlights how mergers may drive important physical changes in galaxies without pushing them off the main sequence.
  • No Thumbnail Available
    Item
    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].
  • Thumbnail Image
    Item
    SEARCH FOR [CII] EMISSION IN z=6.5-11 STAR-FORMING GALAXIES
    (2014) González López, Jorge; Riechers, Dominik A.; Decarli, Roberto; Walter, Fabian; Vallini, Livia; Neri, Roberto; Bertoldi, Frank; Bolatto, Alberto D.; Carilli, Christopher L.; Cox, Pierre; Cunha, Elisabete da; Ferrara, Andrea; Gallerani, Simona; Infante Lira, Leopoldo
  • No Thumbnail Available
    Item
    The Atacama Cosmology Telescope: CO(J=3-2) Mapping and Lens Modeling of an ACT-selected Dusty Star-forming Galaxy
    (2019) Rivera, Jesus; Baker, Andrew J.; Gallardo, Patricio A.; Gralla, Megan B.; Harris, Andrew, I; Huffenberger, Kevin M.; Hughes, John P.; Keeton, Charles R.; Lopez-Caraballo, Carlos H.; Marriage, Tobias A.; Partridge, Bruce; Sievers, Jonathan L.; Tagore, Amitpal S.; Walter, Fabian; Weiss, Axel; Wollack, Edward J.
    We report Northern Extended Millimeter Array CO(J = 3 - 2) observations of the dusty star-forming galaxy ACT-S J020941+001557 at z = 2.5528, which was detected as an unresolved source in the Atacama Cosmology Telescope (ACT) equatorial survey. Our spatially resolved spectral line data support the derivation of a gravitational lens model from 37 independent velocity channel maps using a pixel-based algorithm, from which we infer a velocity-dependent magnification factor mu approximate to 7-22 with a luminosity-weighted mean approximate to 13. The resulting source-plane reconstruction is consistent with a rotating disk, although other scenarios cannot be ruled out by our data. After correction for lensing, we derive a line luminosity LCO(3-2)' = (5.53 +/- 0.69) x 10(10) K km s(-1) pc(2), a cold gas mass M-gas = (3.86 +/- 0.33) x 10(10) M-circle dot, a dynamical mass M-dyn sin(2) i = 3.9(-1.5)(+1.8) x 10(10) M-circle dot, and a gas mass fraction f(gas) csc(2) i = 1.0(-0.4)(+0.8). The line brightness temperature ratio of r(3,1) approximate to 1.6 relative to a Green Bank Telescope CO(J = 1 - 0) detection may be elevated by a combination of external heating of molecular clouds, differential lensing, and/or pointing errors.