Tracing Ram-Pressure Stripping with Warm Molecular Hydrogen Emission

Abstract

We use the Spitzer Infrared Spectrograph (IRS) to study four infalling cluster galaxies with signatures of on-going ram-pressure stripping. H${}_2$ emission is detected in all four; two show extraplanar H${}_2$ emission. The emission usually has a warm (T $\sim$ $115-160$K) and a hot (T $\sim$ 400 $-$ 600K) component that is approximately two orders of magnitude less massive than the warm one. The warm component column densities are typically $10^{19}-10^{20}$ cm${}^{-2}$ with masses of $10^6-10^8{M}_{\odot }$. The warm H${}_2$ is anomalously bright compared with normal star-forming galaxies and therefore may be excited by ram-pressure. In the case of CGCG 97-073, the H${}_2$ is offset from the majority of star formation along the direction of the galaxy's motion in the cluster, suggesting it is forming in the ram-pressure wake of the galaxy. Another galaxy, NGC 4522, exhibits a warm H${}_2$ tail approximately 4 kpc in length. These results support the hypothesis that H${}_2$ within these galaxies is shock-heated from the interaction with the intracluster medium. Stripping of dust is also a common feature of the galaxies. For NGC 4522, where the distribution of dust at 8 $\mu$m is well resolved, knots and ripples demonstrate the turbulent nature of the stripping process. The H$\alpha$ and 24 $\mu$m luminosities show that most of the galaxies have star formation rates comparable to similar mass counterparts in the field. Finally, we suggest a possible evolutionary sequence primarily related to the strength of ram-pressure a galaxy experiences to explain the varied results observed in our sample.

26 pages, 22 figures, accepted for publication in ApJ

References in corpus (16)

• UV Star Formation Rates in the Local Universe
• The MAPPINGS III Library of Fast Radiative Shock Models
• Spectral Mapping Reconstruction of Extended Sources
• The strong transformation of spiral galaxies infalling into massive clusters at z~0.2
• Powerful High Velocity-Dispersion Molecular Hydrogen Associated with an Intergalactic Shock Wave in Stephan's Quintet
• Collisional heating as the origin of filament emission in galaxy clusters
• Mid-Infrared Spectral Diagnostics of Nuclear and Extra-Nuclear Regions in Nearby Galaxies
• Ram-pressure stripped molecular gas in the Virgo spiral galaxy NGC 4522
• IR observations of MS 1054-03: Star Formation and its Evolution in Rich Galaxy Clusters
• Discovery of atomic and molecular mid infra-red emission lines in off-nuclear regions of NGC 1275 and NGC 4696 with the Spitzer Space Telescope
• Ram pressure stripping of disc galaxies orbiting in clusters. II. Galactic wakes
• The origin of molecular hydrogen emission in cooling-flow filaments
• A Large Mass of H2 in the Brightest Cluster Galaxy in Zwicky 3146
• Elemental Abundances of Blue Compact Dwarfs from mid-IR Spectroscopy with Spitzer
• The old globular cluster system of the dIrr galaxy NGC1427A in the Fornax cluster
• Nearby Galaxies in the 2micron All Sky Survey I. K-band Luminosity Functions

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• The MeerKAT Fornax Survey -- I. Survey description and first evidence of ram pressure in the Fornax galaxy cluster