Measurements of CO redshifts with Z-Spec for lensed submillimeter galaxies discovered in the H-ATLAS survey

Autor: Lupu, R. E., Scott, K. S., Aguirre, J. E., Aretxaga, I., Auld, R., Barton, E., Beelen, A., Bertoldi, F., Bock, J. J., Bonfield, D., Bradford, C. M., Buttiglione, S., Cava, A., Clements, D. L., Cooke, J., Cooray, A., Dannerbauer, H., Dariush, A., De Zotti, G., Dunne, L., Dye, S., Eales, S., Frayer, D., Fritz, J., Glenn, J., Hughes, D. H., Ibar, E., Ivison, R. J., Jarvis, M. J., Kamenetzky, J., Kim, S., Lagache, G., Leeuw, L., Maddox, S., Maloney, P. R., Matsuhara, H., Murphy, E. J., Naylor, B. J., Negrello, M., Nguien, H., Omont, A., Pascale, E., Pohlen, M., Rigby, E., Rodighiero, G., Serjeant, S., Smith, D., Temi, P., Thompson, M., Valtchanov, I., Verma, A., Vieira, J. D., Zmuidzinas, J.
Rok vydání: 2010
Předmět:
Druh dokumentu: Working Paper
DOI: 10.1088/0004-637X/757/2/135
Popis: We present new observations from Z-Spec, a broadband 185-305 GHz spectrometer, of five sub-millimeter bright lensed sources selected from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) science demonstration phase (SDP) catalog. We construct a redshift finding algorithm using combinations of the signal-to-noise of all the lines falling in the Z-Spec bandpass to determine redshifts with high confidence, even in cases where the signal-to-noise in individual lines is low. We measure the dust continuum in all sources and secure CO redshifts for four out of five (z~1.5-3). In one source, SDP.17, we tentatively identify two independent redshifts and a water line, confirmed at z=2.308. Our sources have properties characteristic of dusty starburst galaxies, with magnification-corrected star formation rates of 10^(2-3) M_sun/yr. Lower limits for the dust masses (~a few 10^8 M_sun) and spatial extents (~1 kpc equivalent radius) are derived from the continuum spectral energy distributions, corresponding to dust temperatures between 54 and 69K. In the LTE approximation, we derive relatively low CO excitation temperatures (< 100 K) and optical depths (tau<1). Performing a non-LTE excitation analysis using RADEX, we find that the CO lines measured by Z-Spec (from J=4->3 to 10->9, depending on the galaxy) localize the best solutions to either a high-temperature / low-density region, or a low-temperature / high-density region near the LTE solution, with the optical depth varying accordingly. Observations of additional CO lines, CO(1-0) in particular, are needed to constrain the non-LTE models.
Comment: 28 pages, 15 figures, accepted for publication in ApJ, October 1, 2012, Issue 757 - 2
Databáze: arXiv
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