1202.0997 (I. Oteo et al.)

PACS-Herschel FIR detections of Lyman-alpha emitters at 2.0    [PDF]

I. Oteo, A. Bongiovanni, A. M. Pérez García, J. Cepa, A. Ederoclite, M. Sánchez-Portal, I. Pintos-Castro, R. Pérez-Martínez, B. Altieri, P. Andreani, H. Aussel, S. Berta, A. Cimatti, E. Daddi, D. Elbaz, N. Förster Schreiber, R. Genzel, D. Lutz, B. Magnelli, R. Maiolino, A. Poglitsch, P. Popesso, F. Pozzi, E. Sturm, L. Tacconi, I. Valtchanov

In this work we analyze the physical properties of a sample of 56 spectroscopically selected star-forming (SF) Ly$\alpha$ emitting galaxies at 2.0$\lesssim$z$\lesssim$3.5 using both a spectral energy distribution (SED) fitting procedure from rest-frame UV to mid-IR and direct 160$\mu$m observations taken with the Photodetector Array Camera & Spectrometer (PACS) instrument onboard \emph{Herschel Space Observatory}. We define LAEs as those Ly$\alpha$ emitting galaxies whose rest-frame Ly$\alpha$ equivalent widths (Ly$\alpha$ EW$_{rest-frame}$) are above 20\AA, the typical threshold in narrow-band searches. Ly$\alpha$ emitting galaxies with Ly$\alpha$ EW$_{rest-frame}$ are called non-LAEs. As a result of an individual SED fitting for each object, we find that the studied sample of LAEs contains galaxies with ages mostly below 100Myr and a wide variety of dust attenuations, SFRs, and stellar masses. The heterogeneity in the physical properties is also seen in the morphology, ranging from bulge-like galaxies to highly clumpy systems. In this way, we find that LAEs at 2.0$\lesssim$z$\lesssim$3.5 are very diverse, and do not have a bimodal nature, as suggested in previous works. Furthermore, the main difference between LAEs and non-LAEs is their dust attenuation, because LAEs are not as dusty as non-LAEs. On the FIR side, four galaxies of the sample (two LAEs and two non-LAEs) have PACS-FIR counterparts. Their total IR luminosity place all of them in the ULIRG regime and are all dusty objects, with A$_{1200}$$\gtrsim$4mag. This is an indication from direct FIR measurements that dust and Ly$\alpha$ emission are not mutually exclusive. This population of red and dusty LAEs is not seen at z$\sim$0.3, suggesting an evolution with redshift of the IR nature of galaxies selected via their Ly$\alpha$ emission.

View original: http://arxiv.org/abs/1202.0997