Infrared Emission from Dust in the Coma Cluster of Galaxies
Abstract
The reported visual extinction (A_v_ ~ 0.2^m^) of distant clusters seen through the Coma cluster suggests that dust may be present in the hot X-ray-emitting intracluster gas. However, IRAS failed to detect any infrared emission from the cluster at the level expected from the extinction measurements. We present here detailed calculations of the infrared emission from collisionally heated dust in the cluster. Our model includes continuous dust injection from galaxies, grain destruction by sputtering, and transient grain heating by the hot plasma. Our computed infrared fluxes are in agreement with the upper limits obtained from the IRAS. The calculations, and constraints implied by the IRAS observations, suggest that the intracluster dust in the central region of the cluster must be significantly depleted compared to interstellar abundances. The observed visual extinction can therefore not be attributed to the presence of dust in that region. Extinction due to cluster galaxies or their haloes is ruled out as well. The only alternative explanation is that the extinction is caused by dust at great distances (R >= 2 Mpc) from the cluster center. Only a fraction of the required dust could have been injected by cluster galaxies. Therefore, the observed extinction (if real) requires the presence of a hitherto undetected large mass of gas in the outer regions of the cluster. Other implications of our model, such as cluster cooling by gas-grain collisions and the effect of the dust on the distortion of the cosmic microwave background (CMB) radiation seen through the cluster, are also discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1990
- DOI:
- 10.1086/168364
- Bibcode:
- 1990ApJ...350..104D
- Keywords:
-
- Cosmic Dust;
- Galactic Clusters;
- Gas Flow;
- Infrared Astronomy;
- Infrared Radiation;
- Temperature Distribution;
- Astrophysics;
- COSMIC BACKGROUND RADIATION;
- GALAXIES: CLUSTERING;
- GALAXIES: INTERGALACTIC MEDIUM;
- INFRARED: SOURCES;
- INTERSTELLAR: GRAINS