Showing papers by "Matt Bothwell published in 2017"

ISM properties of a massive dusty star-forming galaxy discovered at z ∼ 7.

Abstract: International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the University of Bonn; International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the University of Cologne; FONDECYT [1140099]; U.S. National Science Foundation [AST-1312950]; ERC Advanced Investigator programme DUSTYGAL [321334]; Simons Foundation; NSF [AST-1009452, AST-1445357]; NASA HST from the Space Telescope Science Institute [AR-13906.001]; NASA [NAS5-26555]; Cottrell College Science Award - Research Corporation for Science Advancement; Commonwealth of Australia; National Science Foundation [PLR-1248097]; Kavli Foundation; Gordon and Betty Moore Foundation [GBMF 947]; [PHY-1125897]

ALMA observations of atomic carbon in z ∼ 4 dusty star-forming galaxies

Abstract: National Science Foundation [PLR-1248097, PHY-1125897]; Kavli Foundation; Gordon and Betty Moore Foundation [GBMF 947]; STFC [ST/M001172/1, ST/K003119/1]; US National Science Foundation [AST-1312950]; FONDECYT [1140099]

ISM properties of a Massive Dusty Star-Forming Galaxy discovered at z ~ 7

Abstract: We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy (DSFG) to date, SPT-S J031132-5823.4 (hereafter SPT0311-58), at $z=6.900 +/- 0.002$. SPT0311-58 was discovered via its 1.4mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an ALMA 3mm frequency scan that detected CO(6-5), CO(7-6) and [CI](2-1), and subsequently confirmed by detections of CO(3-2) with ATCA and [CII] with APEX. We constrain the properties of the ISM in SPT0311-58 with a radiative transfer analysis of the dust continuum photometry and the CO and [CI] line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311-58 is extremely massive, with an intrinsic gas mass of $M_{\rm gas} = 3.3 \pm 1.9 \times10^{11}\,M_{\odot}$. Its large mass and intense star formation is very rare for a source well into the Epoch of Reionization.

SDSS-IV MaNGA-resolved Star Formation and Molecular Gas Properties of Green Valley Galaxies: A First Look with ALMA and MaNGA

Abstract: We study the role of cold gas in quenching star formation in the green valley by analyzing ALMA 12CO (1–0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ( fgas) for these galaxies separately in the central “bulge” regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an “inside-out” model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in fgas is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and fgas on kiloparsec scales—the local SFE or fgas in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by fgas, whereas both SFE and fgas play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of the green valley as a whole.

Resolved star formation and molecular gas properties of green valley galaxies: a first look with ALMA and MaNGA

Abstract: We study the role of cold gas in quenching star formation in the green valley by analysing ALMA $^{12}$CO (1-0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ($f_{\rm~gas}$) for these galaxies separately in the central `bulge' regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an `inside-out' model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in $f_{\rm~gas}$ is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and $f_{\rm~gas}$ on kpc scales -- the local SFE or $f_{\rm~gas}$ in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by $f_{\rm~gas}$, whereas both SFE and $f_{\rm~gas}$ play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of green valley as a whole.

The final data release of ALLSMOG: a survey of CO in typical local low-M∗ star-forming galaxies

Abstract: We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2–1) emission line observations of 88 nearby, low-mass (1085 ∗ [M ⊙ ] ) star-forming galaxies carried out with the 230 GHz APEX-1 receiver on the APEX telescope The main goal of ALLSMOG is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous CO surveys We also present IRAM 30 m observations of the CO(1–0) and CO(2–1) emission lines in nine galaxies aimed at increasing the M ∗ M ⊙ sample size In this paper we describe the observations, data reduction and analysis methods and we present the final CO spectra together with archival Hi 21 cm line observations for the entire sample of 97 galaxies At the sensitivity limit of ALLSMOG, we register a total CO detection rate of 47% Galaxies with higher M ∗ , SFR, nebular extinction (A V ), gas-phase metallicity (O/H), and Hi gas mass have systematically higher CO detection rates In particular, the parameter according to which CO detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work We investigate scaling relations between the CO(1–0) line luminosity (L'CO(1-0) ) and galaxy-averaged properties using ALLSMOG and a sub-sample of COLD GASS for a total of 185 sources that probe the local main sequence (MS) of star-forming galaxies and its ± 03 dex intrinsic scatter from M ∗ = 1085 M ⊙ to M ∗ = 1011 M ⊙ L'CO(1-0) is most strongly correlated with the SFR, but the correlation with M ∗ is closer to linear and almost comparably tight The relation between L'CO(1-0) and metallicity is the steepest one, although deeper CO observations of galaxies with A V V Our results suggest that star-forming galaxies across more than two orders of magnitude in M ∗ obey similar scaling relations between CO luminosity and the galaxy properties examined in this work Besides SFR, the CO luminosity is likely most fundamentally linked to M ∗ , although we note that stellar mass alone cannot explain all of the variation in CO emission observed as a function of O/H and M HI

The final data release of ALLSMOG: a survey of CO in typical local low-M* star-forming galaxies

Abstract: We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2-1) emission line observations of 88 nearby, low-mass (10^8.5

Resolved star formation and molecular gas properties of green valley galaxies: a first look with ALMA and MaNGA

Abstract: We study the role of cold gas in quenching star formation in the green valley by analysing ALMA $^{12}$CO (1-0) observations of three galaxies with resolved optical spectroscopy from the MaNGA survey. We present resolution-matched maps of the star formation rate and molecular gas mass. These data are used to calculate the star formation efficiency (SFE) and gas fraction ($f_{\rm~gas}$) for these galaxies separately in the central `bulge' regions and outer disks. We find that, for the two galaxies whose global specific star formation rate (sSFR) deviates most from the star formation main sequence, the gas fraction in the bulges is significantly lower than that in their disks, supporting an `inside-out' model of galaxy quenching. For the two galaxies where SFE can be reliably determined in the central regions, the bulges and disks share similar SFEs. This suggests that a decline in $f_{\rm~gas}$ is the main driver of lowered sSFR in bulges compared to disks in green valley galaxies. Within the disks, there exist common correlations between the sSFR and SFE and between sSFR and $f_{\rm~gas}$ on kpc scales -- the local SFE or $f_{\rm~gas}$ in the disks declines with local sSFR. Our results support a picture in which the sSFR in bulges is primarily controlled by $f_{\rm~gas}$, whereas both SFE and $f_{\rm~gas}$ play a role in lowering the sSFR in disks. A larger sample is required to confirm if the trend established in this work is representative of green valley as a whole.

SDSS IV MaNGA: discovery of an Hα blob associated with a dry galaxy pair - ejected gas or a 'dark' galaxy candidate?

Abstract: The work is supported by the Ministry of Science & Technology of Taiwan under the grant MOST 103-2112-M-001-031-MY3. H.F. acknowledges support from the NSF grant AST-1614326 and funds from the University of Iowa. S. Peirani acknowledges support from the Japan Society for the Promotion of Science (JSPS long-term invitation fellowship). J.G.F.-T. is currently supported by the Centre National d'Etudes Spatiales (CNES) through the PhD grant 0101973 and the Region de Franche-Comte and by the French Programme National de Cosmologie et Galaxies (PNCG). Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the participating institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah.

SDSS IV MaNGA: Discovery of an $H_{\alpha}$ blob associated with a dry galaxy pair -- ejected gas or a `dark' galaxy candidate?

Abstract: We report the discovery of a mysterious giant $H_{\alpha}$ blob that is $\sim 8$ kpc away from the main MaNGA target 1-24145, one component of a dry galaxy merger, identified in the first-year SDSS-IV MaNGA data. The size of the $H_{\alpha}$ blob is $\sim$ 3-4 kpc in radius, and the $H_{\alpha}$ distribution is centrally concentrated. However, there is no optical continuum counterpart in deep broadband images reaching $\sim$26.9 mag arcsec$^{-2}$ in surface brightness. We estimate that the masses of ionized and cold gases are $3.3 \times 10^{5}$ $\rm M_{\odot}$ and $< 1.3 \times 10^{9}$ $\rm M_{\odot}$, respectively. The emission-line ratios indicate that the $H_{\alpha}$ blob is photoionized by a combination of massive young stars and AGN. Furthermore, the ionization line ratio decreases from MaNGA 1-24145 to the $H_{\alpha}$ blob, suggesting that the primary ionizing source may come from MaNGA 1-24145, likely a low-activity AGN. Possible explanations of this $H_{\alpha}$ blob include AGN outflow, the gas remnant being tidally or ram-pressure stripped from MaNGA 1-24145, or an extremely low surface brightness (LSB) galaxy. However, the stripping scenario is less favoured according to galaxy merger simulations and the morphology of the $H_{\alpha}$ blob. With the current data, we can not distinguish whether this $H_{\alpha}$ blob is ejected gas due to a past AGN outburst, or a special category of `ultra-diffuse galaxy' (UDG) interacting with MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA 1-24145.