Herschel-PACS far-infrared detections of Lyman-α emitters at 2.0 ≲ z ≲ 3.5
In this work we analyse the physical properties of a sample of 56
spectroscopically selected star-forming (SF) Lyα emitting galaxies
at 2.0 ≲ z ≲ 3.5 using both a spectral energy distribution
(SED) fitting procedure from rest-frame UV to mid-IR and direct 160
μm FIR observations taken with the Photodetector Array Camera and
Spectrometer (PACS) instrument onboard the Herschel Space Observatory.
We define LAEs as those Lyα-emitting galaxies whose rest-frame
Lyα equivalent widths (Lyα EW<SUB>rest – frame</SUB>) are
above 20 Å, the typical threshold in narrow-band searches.
Lyα-emitting galaxies with Lyα EW<SUB>rest – frame</SUB>
< 20 Å are called non-LAEs. As a result of an individual SED
fit for each object, we find that the studied sample of LAEs contains
galaxies with ages mostly below 100 Myr and a wide variety of dust
attenuations, SFRs, and stellar masses. The heterogeneity of 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 ≲ z ≲ 3.5 are very diverse, and do not have a
bimodal nature, as suggested in previous studies. 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 detections. Their total IR
luminosities place all of them in the ULIRG regime, and all are dusty
objects, with A<SUB>1200</SUB> ≳ 4 mag. This is an indication from
direct FIR measurements that dust and Lyα emission are not
mutually exclusive. This population of red and dusty LAEs is not seen at
z ~ 0.3, which suggests an evolution with redshift of the IR nature of
galaxies selected via their Lyα emission.
Herschel is an ESA space observatory with science instruments provided
by European-led Principal Investigator consortia and with important
participation from NASA.Appendix A is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>