Continuum Emission by Cooling Clouds

TL;DR

This paper investigates the UV and Lyman Alpha emission from cooling baryonic clouds in dark matter halos, showing their observable properties and spectral features that distinguish them from star-forming galaxies.

Contribution

It presents a model predicting the luminosity, equivalent width, and spectral characteristics of cooling clouds, highlighting their detectability and unique spectral signatures.

Findings

Lya luminosities can reach 10^42-10^43 erg/s in halos of 10^11-10^12 solar masses.

Cooling clouds exhibit a high Lya equivalent width of about 400 Angstroms.

Two-photon transitions dominate the UV spectrum, differentiating cooling clouds from star-forming galaxies.

Abstract

The collapse of baryons into the center of a host dark matter halo is accompanied by radiation that may be detectable as compact (< 10 kpc) UV-continuum and Lyman Alpha (hereafter Lya) emission with Lya luminosities as high as ~1e42-1e43 erg/s in halos of mass M=1e11-10e12 solar masses. We show that the observed equivalent width (EW) of the Lya line emitted by these cooling clouds is EW 400 Angstrom (restframe). These luminosities and EWs are comparable to those detected in narrowband surveys for redshifted Lya emission. The rest-frame ultraviolet of Lya emitting cooling clouds radiation may be dominated by two-photon transitions from 2s->1s. The resulting spectrum can distinguish cooling clouds from a broad class of young star forming galaxies.