GASP I: Gas stripping phenomena in galaxies with MUSE (1704.05086v2)

Abstract: GASP (GAs Stripping Phenomena in galaxies with MUSE) is a new integral-field spectroscopic survey with MUSE at the VLT aiming at studying gas removal processes in galaxies. We present an overview of the survey and show a first example of a galaxy undergoing strong gas stripping. GASP is obtaining deep MUSE data for 114 galaxies at z=0.04-0.07 with stellar masses in the range 10^9.2-10^11.5 M_sun in different environments (galaxy clusters and groups, over more than four orders of magnitude in halo mass). GASP targets galaxies with optical signatures of unilateral debris or tails reminiscent of gas stripping processes ("jellyfish galaxies"), as well as a control sample of disk galaxies with no morphological anomalies. GASP is the only existing Integral Field Unit (IFU) survey covering both the main galaxy body and the outskirts and surroundings, where the IFU data can reveal the presence and the origin of the outer gas. To demonstrate GASP's ability to probe the physics of gas and stars, we show the complete analysis of a textbook case of a "jellyfish" galaxy, JO206. This is a massive galaxy (9 x 10^10 M_sun in a low-mass cluster (sigma ~500 km/s), at a small projected clustercentric radius and a high relative velocity, with >=90kpc-long tentacles of ionized gas stripped away by ram pressure. We present the spatially resolved kinematics and physical properties of gas and stars, and depict the evolutionary history of this galaxy.

Overview of the GASP I: Gas Stripping Phenomena in Galaxies with MUSE

The paper "GASP I: Gas Stripping Phenomena in Galaxies with MUSE" introduces an integral-field spectroscopic survey conducted with the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). The objective of the GASP survey is to observe and analyze the gas removal processes in galaxies across various environments, unraveling the physical mechanisms involved and their consequences on galactic evolution.

Survey Design and Objectives

The GASP survey targets 114 galaxies within a redshift range of z=0.04-0.07, covering a wide stellar mass range from $10^{9.2}$ to $10^{11.5} M_{\odot}$. The survey includes galaxies situated in diverse environments such as galaxy clusters and groups. GASP aims to capture both galaxies exhibiting optical signatures of unilateral gas debris (known as "jellyfish galaxies") and a control set of disk galaxies without morphological anomalies. A key feature of this survey is its unique ability to map the main body of galaxies as well as their outskirts, providing insights into the outer gas distribution and its origins.

Analysis of JO206: A Case Study

The paper provides an in-depth analysis of a representative jellyfish galaxy, JO206, elucidating the survey's capacity to probe gas dynamics and interactions with its stellar environment. JO206, a massive galaxy located in a low-mass cluster, displays significant gas stripping phenomena, with ionized gas tentacles extending over 90 kpc due to ram pressure stripping. The paper highlights the galaxy's gas kinematics, characterized by coherent rotation extending far into the stripped tails, in contrast to the regular stellar kinematics indicative of ram pressure influencing only the gaseous component. The AGN activity present at JO206’s core contributes to the central ionization, while star formation largely governs the gas ionization beyond the disk.

Key Findings and Implications

JO206 exemplifies strong ram pressure stripping in a low-mass cluster context, a phenomenon traditionally associated with more massive clusters. The paper highlights:

• The existence of significant star formation in situ within the stripped gas, bolstering the hypothesis that new stars form in the interpolated regions.
• The spatially resolved metallicity variations in JO206, from metal-rich regions in the disk to metal-poor zones in the tails, reflecting the sequential stripping of outer, less-massive gas layers.
• The substantial role of environment in determining gas stripping efficiency, emphasizing the impact of cluster-centric position and velocity.

Future Directions

The GASP survey’s findings suggest numerous pathways for future research. Expanding the observational dataset to integrate multiwavelength studies, including molecular and neutral gas observations, can significantly enrich the understanding of the interplay between different gas phases during galaxy evolution. Moreover, the potential linkages between gas stripping and AGN activity warrant further exploration to construe the role environmental factors play in galactic nuclear activity.

The GASP I paper delivers a comprehensive framework for studying gas stripping in various environmental contexts, underscoring the need for integrated spectroscopic investigations to decode the complex processes shaping galaxy evolution.