CONSTRAINING DUST AND MOLECULAR GAS PROPERTIES IN Lyα BLOBS AT<i>z</i>∼ 3

Abstract

In order to constrain the bolometric luminosities, dust properties and\nmolecular gas content of giant Lyman alpha nebulae, the so-called Lyman alpha\nblobs, we have carried out a study of dust continuum and CO line emission in\ntwo well-studied representatives of this population at z ~ 3: a Lya blob\ndiscovered by its strong Spitzer MIPS 24um detection (LABd05; Dey et al. 2005)\nand the Steidel blob 1 (SSA22-LAB01; Steidel et al. 2000). We find that the\nspectral energy distribution of LABd05 is well described by an AGN-starburst\ncomposite template with L(FIR) = (4.0 +/- 0.5) x 10^12 Lsun, comparable to\nhigh-z sub-millimeter galaxies and ultraluminous infrared galaxies. New\nAPEX/LABOCA 870um measurements rule out the reported SCUBA detection of the\nSSA22-LAB01 (S[850um] = 16.8 mJy) at the &gt; 4sigma level. Consistent with this,\nultra-deep Plateau de Bure Interferometer (PdBI) observations with ~2arcsec\nspatial resolution also fail to detect any 1.2mm continuum source down to\n~0.45mJy per beam (3sigma). Combined with the existing (sub)mm observations in\nthe literature, we conclude that the FIR luminosity of SSA22-LAB01 remains\nuncertain. No CO line is detected in either case down to integrated flux limits\nof (Snu dV) &lt; 0.25--1.0 Jy km/s, indicating a modest molecular gas reservoir,\nM(H_2) &lt; 1--3 x 10^10 Msun. The non-detections exclude, with high significance\n(12 sigma), the previous tentative detection of a CO(4-3) line in the\nSSA22-LAB01. The increased sensitivity afforded by ALMA will be critical in\nstudying molecular gas and dust in these interesting systems.\n