A Search for Dust Emission in the Leo Intergalactic Cloud

TL;DR

This study searches for infrared dust emission in the Leo intergalactic cloud using Spitzer data, finding tentative evidence of dust that suggests the cloud is formed through galaxy interactions rather than primordial origins.

Contribution

First infrared search for dust in the Leo cloud, providing constraints on dust content and implications for its origin.

Findings

Possible detection of dust at 8 microns

Upper limits on dust emission at 70 and 160 microns

Dust-to-gas ratio could be up to a few times solar

Abstract

We present a search for infrared dust emission associated with the Leo cloud, a large intergalactic cloud in the M96 group. Mid-infrared and far-infrared images were obtained with IRAC and MIPS on the Spitzer Space Telescope. Our analysis of these maps is done at each wavelength relative to the HI spatial distribution. We observe a probable detection at 8 microns and a marginal detection at 24 microns associated with the highest HI column densities in the cloud. At 70 and 160 microns, upper limits on the dust emission are deduced. The level of the detection is low so that the possibility of a fortuitous cirrus clump or of an overdensity of extragalactic sources along the line of sight can not be excluded. If this detection is confirmed, the quantities of dust inferred imply a dust to gas ratio in the intergalactic cloud up to a few times solar but no less than 1/20 solar. A confirmed detection would therefore exclude the possibility that the intergalactic cloud has a primordial origin. Instead, this large intergalactic cloud could therefore have been formed through interactions between galaxies in the group.