MMTF-Halpha and HST-FUV Imaging of the Filamentary Complex in Abell 1795

TL;DR

This study uses high-resolution imaging to analyze filamentary structures in Abell 1795, revealing their composition, star formation activity, and ionization mechanisms, suggesting cosmic rays play a significant role.

Contribution

First detailed high-resolution imaging of filaments in Abell 1795 at multiple wavelengths, revealing their structure, star formation, and ionization processes.

Findings

Filaments are thin, intertwined, extending ~50 kpc, with widths <1 kpc.

Star formation occurs within filaments at a rate much lower than predicted by X-ray data.

Ionization is likely dominated by cosmic ray heating rather than stellar photoionization.

Abstract

We have obtained deep, high spatial resolution images of the central region of Abell 1795 at Halpha and [NII] (6583A) with the Maryland Magellan Tunable Filter (MMTF), and in the far-ultraviolet (FUV) with the Advanced Camera for Surveys Solar Blind Channel on the Hubble Space Telescope (HST). The superb image quality of the MMTF data has made it possible to resolve the known SE filament into a pair of thin, intertwined filaments extending for ~50 kpc, with a width < 1 kpc. The presence of these thin, tangled strands is suggestive of a cooling wake where runaway cooling is taking place, perhaps aided by an enhanced magnetic field in this region. The HST data further resolve these strands into chains of FUV-bright stellar clusters, indicating that these filaments are indeed sites of on-going star formation, but at a rate ~2 orders of magnitude smaller than the mass-deposition rates predicted from the X-ray data. The elevated [NII]/Halpha ratio and large spatial variations of the FUV/Halpha flux ratio across the filaments indicate that O-star photoionization is not solely responsible for the ionization. The data favor collisional heating by cosmic rays either produced in-situ by magnetohydrodynamical processes or conducted in from the surrounding intracluster medium.