A BLIND GREEN BANK TELESCOPE MILLIMETER-WAVE SURVEY FOR REDSHIFTED MOLECULAR ABSORPTION

作者：Kanekar N^*; Gupta A; Carilli C L; Stocke J T; Willett K W

来源：Astrophysical Journal, 2014, 782(1): 56.

DOI：10.1088/0004-637X/782/1/56

• galaxies: high-redshift
• molecular processes
• quasars: absorption lines

We present the methodology for %26quot;blind%26quot; millimeter-wave surveys for redshifted molecular absorption in the CO/HCO+ rotational lines. The frequency range 30-50 GHz appears optimal for such surveys, providing sensitivity to absorbers at z greater than or similar to 0.85. It is critical that the survey is %26quot;blind,%26quot; i.e., based on a radio-selected sample, including sources without known redshifts. We also report results from the first large survey of this kind, using the Q-band receiver on the Green Bank Telescope (GBT) to search for molecular absorption toward 36 sources, 3 without known redshifts, over the frequency range 39.6-49.5 GHz. The GBT survey has a total redshift path of Delta z approximate to 24, mostly at 0.81 %26lt; z %26lt; 1.91, and a sensitivity sufficient to detect equivalent H-2 column densities greater than or similar to 3 x 10(21) cm(-2) in absorption at 5 sigma significance (using CO-to-H-2 and HCO+-to-H-2 conversion factors of the Milky Way). The survey yielded no confirmed detections of molecular absorption, yielding the 2 sigma upper limit n(z = 1.2) %26lt; 0.15 on the redshift number density of molecular gas at column densities N(H-2) greater than or similar to 3 x 10(21) cm(-2).

• 出版日期2014-2-10