Astrophys. J., 779, 65 (2013/December-2)
Narrowband Lyman-continuum imaging of galaxies at z ∼ 2.85.
MOSTARDI R.E., SHAPLEY A.E., NESTOR D.B., STEIDEL C.C., REDDY N.A. and TRAINOR R.F.
Abstract (from CDS):
We present results from a survey for z ∼ 2.85 Lyman-continuum (LyC) emission in the HS1549+1933 field and place constraints on the amount of ionizing radiation escaping from star-forming galaxies. Using a custom narrowband filter (NB3420) tuned to wavelengths just below the Lyman limit at z ≥ 2.82, we probe the LyC spectral region of 49 Lyman break galaxies (LBGs) and 91 Lyα emitters (LAEs) spectroscopically confirmed at z ≥ 2.82. Four LBGs and seven LAEs are detected in NB3420. Using V-band data probing the rest-frame nonionizing UV, we observe that many NB3420-detected galaxies exhibit spatial offsets between their LyC and nonionizing UV emission and are characterized by extremely blue NB3420-V colors, corresponding to low ratios of nonionizing to ionizing radiation (FUV/FLyC) that are in tension with current stellar population synthesis models. We measure average values of (FUV/FLyC) for our LBG and LAE samples, correcting for foreground galaxy contamination and H I absorption in the intergalactic medium. We find (FUV/FLyC)corr_LBG = 82±45 and (FUV/FLyC)corr_LAE = 7.4 ±3.6 . These flux density ratios correspond, respectively, to relative LyC escape fractions of f_esc, rel_LBG = 5% -8%, and f_esc, rel_LAE = 18% - 49% absolute LyC escape fractions of f_esc, rel_LBG = 1%-2% and f_esc, rel_LAE = 5% - 15%, and a comoving LyC emissivity from star-forming galaxies of 8.8-15.0 x1024 erg/s/Hz M/pc3. In order to study the differential properties of galaxies with and without LyC detections, we analyze narrowband Lyα imaging and rest-frame near-infrared imaging, finding that while LAEs with LyC detections have lower Lyα equivalent widths on average, there is no substantial difference in the rest-frame near-infrared colors of LBGs or LAEs with and without LyC detections. These preliminary results are consistent with an orientation-dependent model where LyC emission escapes through cleared paths in a patchy interstellar medium.
cosmology: observations - diffuse radiation - galaxies: high-redshift - intergalactic medium
VizieR on-line data:
<Available at CDS (J/ApJ/779/65): table3.dat table4.dat table8.dat table9.dat>
Table 3: [MSN2013] BXNN (No BX84), [MSN2013] MDNN N=5 among (Nos MD5-MD34), [MSN2013] CNN N=20 among (Nos C1-C27), [MSN2013] DNN N=16 among (Nos D3-D27), [MSN2013] MNN N=7 among (Nos M2-M23). Table 4: [MSN2013] laeNNNN N=91 among (Nos lae32-lae8993). Table 8: [MSN2013] GNBNNNN N=3 among (Nos 2861-5270), [MSN2013] laeNNNN N=5 among (Nos lae1670-lae7890). Table 9: [MSN2013] laeNNNN N=33 among (Nos lae759-lae7642).
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