Browsing by Author "Walter, Fabian"

Now showing 1 - 8 of 8
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    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
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    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
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    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
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    Discovery and characterization of 25 new quasars at 4.6 < z < 6.9 from wide-field multiband surveys
    (2025) Belladitta, Silvia; Bañados, Eduardo; Xie, Zhang-Liang; Decarli, Roberto; Onorato, Silvia; Yang, Jinyi; Bischetti, Manuela; Onoue, Masafusa; Loiacono, Federica; Martínez Ramirez, Laura Natalia; Mazzucchelli, Chiara; Davies, Frederick B.; Wolf, Julien; Schindler, Jan-Torge; Fan, Xiaohui; Wang, Feige; Walter, Fabian; Mkrtchyan, Tatevik; Stern, Daniel; Farina, Emanuele P.; Venemans, Bram P.
    Luminous quasars at provide key insights into the early Universe. Their rarity necessitates wide-field multi-band surveys to efficiently separate them from the main astrophysical contaminants (i.e., ultracool dwarfs). To expand the sample of high- quasars, we conducted targeted selections using optical, infrared, and radio surveys, complemented by literature-based quasar candidate catalogs. In this paper, we report the discovery of \nqsos\ new quasars at (six at ), with between 25.4 and 27.0. We also present new spectra of six quasars we selected, but whose independent discovery has already been published in the literature. Three of the newly discovered quasars are strong radio emitters (L10erg s Hz). Among them, one source at exhibits typical blazar-like properties, including a flat radio spectrum, radio-loudness 1000, and multi-frequency variability. It is also detected by SRG/eROSITA X-ray telescope (ferg s cm). In addition, for seven quasars we present near-infrared spectroscopy and estimate the central black hole mass from their C and Mg broad emission this http URL masses (log[M]) and Eddington ratios () are consistent with other quasars reported in the literature. A quasar exhibits a velocity difference of approximately km s between the C and Mg emission lines, making it one of the most extreme C outflows currently known. Additionally, the sample includes three high-ionization broad absorption line quasars. One of these quasars shows potential evidence of an extremely fast outflow feature, reaching km s.
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    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.
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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].
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    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
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    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.