Deep Submillimeter and Radio Observations in the SSA22 Field. I. Powering Sources and the Lyα Escape Fraction of Lyα Blobs

Abstract

We study the heating mechanisms and Lyα escape fractions of 35 Lyα blobs (LABs) at z ≈ 3.1 in the SSA22 field. Dust continuum sources have been identified in 11 of the 35 LABs, all with star formation rates (SFRs) above 100M /yr. Likely radio counterparts are detected in 9 out of 29 investigated LABs. The detection of submm dust emission is more linked to the physical size of the Lyα emission than to the Lyα luminosities of the LABs. A radio excess in the submm/radio detected LABs is common, hinting at the presence of active galactic nuclei. Most radio sources without X-ray counterparts are located at the centers of the LABs. However, all X-ray counterparts avoid the central regions. This may be explained by absorption due to exceptionally large column densities along the line-of-sight or by LAB morphologies, which are highly orientation dependent. The median Lyα escape fraction is about 3% among the submm-detected LABs, which is lower than a lower limit of 11% for the submm-undetected LABs. We suspect that the large difference is due to the high dust attenuation supported by the large SFRs, the dense large-scale environment as well as large uncertainties in the extinction corrections required to apply when interpreting optical data.

A high dust emissivity index β for a CO-faint galaxy in a filamentary Lyα nebula at z = 3.1

“…We measured the total flux density of both dust continuum emission using IMFIT task of CASA with primary beam correction (Table 1). We derived an infrared (IR) luminosity L IR [8−1000¯m] , a dust temperature T d and a dust emissivity index β by fitting a single temperature, optically thin modified black body model to the SPIRE 250 µm (Kato et al 2016), ALMA Band 7 850 µm (Ao et al 2017;Matsuda et al in prep), ALMA Band 3 2.7 mm, and 3 mm dust continuum emission (Figure 2). The SPIRE 250 µm flux density is measured at the position of LAB18.b and applied a source confusion noise for photometry error (Kato et al 2016).…”

“…Lyα blobs (LABs) are extended Lyα emitting nebulae, primarily found in galaxy over-dense regions at z ∼ 1 − 3 (e.g., Steidel et al 2000;Matsuda et al 2004;Matsuda et al 2009;Matsuda et al 2011;Dey et al 2005;Prescott et al 2008;Barger, Cowie, & Wold 2012;Valentino et al 2016;Caminha et al 2016;Cai et al 2017). It has been found that some 100 kpc-scale LABs are bright in submillimeter/millimeter wavelengths, suggesting a possible connection between LABs and dusty star-forming galaxies (DSFGs, e.g., Chapman et al 2001;Chapman et al 2004;Geach et al 2005;Geach et al 2014;Tamura et al 2013;Yang et al 2014;Hine et al 2016;Alexander et al 2016;Ao et al 2017;Umehata et al 2017a;Umehata et al 2017b;Umehata et al 2018). However, we don't know if the DSFGs in LABs differ from typical DSFGs population.…”

“…The best-fit single and double Gaussian profiles are overlaid as dashed and solid curves, respectively. Telescope (JCMT) (Chapman et al 2001;Chapman et al 2004;Geach et al 2005;Hine et al 2016;Ao et al 2017) and…”

Discovery of a giant and luminous Lyα+C IV+He II nebula at z = 3.326 with extreme emission line ratios

“…Even considering a possible lensing magnification (µ ∼ 1.5) from the group of z = 0.64 galaxies at ∼ 15 SW, HLock01-LAB is one of the most luminous nebulae know at high redshift. In Figure 8 we compare the maximum projected size of Lyα emission and the total luminosity of HLock01-LAB with a compilation of other giant Lyα nebulae associated with QSOs (Cantalupo et al 2014;Hennawi et al 2015;Borisova et al 2016;Cai et al 2018;Arrigoni Battaia et al 2018), HzRGs (van Ojik et al 1997Reuland et al 2003;Villar-Martín et al 2003, 2007bVenemans et al 2007), and type-II AGNs (Overzier et al 2013;Ao et al 2017;Cai et al 2017). Lyα halos around powerful radio-galaxies show statistically larger Lyα luminosity and broader kinematics with respect to other radio-quiet systems (e.g., Heckman et al 1991a;Miley et al 2006).…”

“…Up: Lyα luminosity and maximum projected extension of HLock01-LAB compared to other Lyα nebula associated with type-II AGNs, QSOs, and HzRGs (see references in the text). Middle: relation between the total radio power and Lyα luminosity of nebulae associated with HzRGs (van Ojik et al 1997) and type-II AGNs (Ao et al 2017). The horizontal dashed line marks the approximate FIRST radio luminosity limit at z ∼ 3 (S 1.4GHz ∼ 0.9 mJy).…”