Constraining the duration of ram pressure stripping from the direction of optical jellyfish galaxy tails



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Universidad de Valparaíso



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Instituto de Fisica y Astronomia




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Within the field of galaxy evolution, we know the life of a galaxy can be driven by a combination of internal and external mechanisms. Amongst the latter, perhaps the most efficient mechanism affecting the gas content and star formation histories of galaxies in dense environments is ram pressure stripping, produced when a galaxy moves through the intergalactic medium within groups and clusters of galaxies. Ex- treme examples of on-going ram pressure stripping are known as jellyfish galaxies, a type of galaxy characterized by a tail of stripped material that can be directly ob- served in multiple wavelengths. Using the largest broad-band optical jellyfish can- didate sample in local clusters known to date, we measure the angle between the direction of the tails visible in the galaxies, and the direction towards the host cluster center. We find that 32.7% of the galaxy tails point away from the cluster center, 18.5% point toward the cluster center, and 48.8% point elsewhere. Moreover, we find strong signatures of ram pressure stripping happening on galaxies pointing away and to- wards the cluster center, and larger velocity dispersion profiles for galaxies with tails pointing away. These results are consistent with a scenario where ram pressure strip- ping has a stronger effect for galaxies following radial orbits on first infall. The results also suggest that in many cases, radially infalling galaxies are able to retain their tails after pericenter and continue to experience significant on-going ram pressure strip- ping. With the observational measures obtained in this work, we then constrain the lifetime of the optical tails from the moment they first appear to the moment they dis- appear, by comparing them with N-body simulations in combination with an MCMC model. We obtain that galaxy tails appear for the first time at ∼ 1.16 R200 and disap- pear ∼ 650 Myr after pericenter. Finally, this work constitutes an important base for future studies with increasingly larger samples of ram pressure stripped galaxies.


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