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    Molecular gas in type 2 quasars at z ~ 0.2-0.3

    Access Status
    Open access via publisher
    Authors
    Villar-Martín, M.
    Rodríguez, M.
    Drouart, Guillaume
    Emonts, B.
    Colina, L.
    Humphrey, A.
    García Burillo, S.
    Graciá Carpio, J.
    Planesas, P.
    Pérez Torres, M.
    Arribas, S.
    Date
    2013
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Villar-Martín, M. and Rodríguez, M. and Drouart, G. and Emonts, B. and Colina, L. and Humphrey, A. and García Burillo, S. et al. 2013. Molecular gas in type 2 quasars at z ~ 0.2-0.3. Monthly Notices of the Royal Astronomical Society. 434 (2): pp. 978-991.
    Source Title
    Monthly Notices of the Royal Astronomical Society
    DOI
    10.1093/mnras/stt1014
    ISSN
    0035-8711
    School
    Curtin Institute of Radio Astronomy (Physics)
    URI
    http://hdl.handle.net/20.500.11937/14972
    Collection
    • Curtin Research Publications
    Abstract

    We present results of CO(1-0) spectroscopic observations of 10 Sloan Digital Sky Survey type 2 quasars (QSO2) at z ~ 0.2-0.3 observed with the 30-m IRAM radio telescope and the Australia Telescope Compact Array. We report five new confirmed CO(1-0) detections and one tentative detection. They have L'CO ~ several × 109 K km s-1 pc2, while upper limits for the non-detections are L'CO < 3s = several × 109 K km s-1 pc2. This study increases the total number of QSO2 with CO measurements at z 1 to 20, with a 50 per cent detection rate. The vast majority are at z ~ 0.1-0.4. Assuming a conversion factor a = 0.8 M?(K km s-1pc2)-1, the implied molecular gas masses are in the range MH2 4 × 108 to ~5 × 109 M?. We compare with samples of type 1 quasars (QSO1), luminous and ultraluminous infrared galaxies. We find no difference in the molecular gas content of QSO1 and QSO2 of a given infrared luminosity, although the QSO2 sample is affected by small number statistics. This result, if confirmed, is consistent with the unification model for quasars. QSO2 fall on the L'COversus z, L'COversus LFIR and ? = LFIR LCO versus LFIR correlations defined by quasars at different z. The location of the QSO2 in these diagrams is discussed in comparison with samples of QSO1, luminous and ultraluminous infrared galaxies, and high-z submm sources. CO(1-0) has full width at half-maximum (FWHM) ~ 180-370 km s-1 when detected, with a variety of kinematic profiles (single or double horned). In general, the CO line is narrower than [O III]5007, as observed in low-z QSO1, with FWHM[O III]/FWHMCO ~ 1-2). This probably reveals different spatial sizes and/or geometry of the ionized and molecular phases and a higher sensitivity of the [O III] emission to non-gravitational motions, such as outflows. Considering the z ~ 0.1-0.4 range, where CO measurements for both QSO1 and QSO2 exist, we find no difference in FWHMCO between them, although this result is tentative. In the unification scenario between QSO1 and QSO2, this suggests that the distribution of CO gas is not related to the obscuring torus. ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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