Star Formation Histories and Stellar Dynamics in the Central Galaxies of RX J0820.9+0752, A1835, and PKS 0745-191

Abstract

We present Keck Cosmic Web Imager observations of stellar populations in three galaxies lying at the centers of cooling flow clusters. All three host rich molecular gas reservoirs and show prominent Balmer absorption from $30-100$ Myr-old stars consistent with long lasting star formation. Two systems, A1835 and PKS 0745$-$191, have spatially extended young stellar populations in their centers with recent star formation rates of 100 M${}_{\odot }$ yr${}^{-1}$ and 8 M${}_{\odot }$ yr${}^{-1}$, respectively. In A1835 we uncover a blueshifted clump of young stars moving at high speed with respect to the gas and central galaxy. We suggest these stars formed in a gaseous outflow and have since detached from their natal gas and are now falling inward. This result indicates that star formation is proceeding in a dynamically complex environment shaped by the central galaxy's motion relative to cooling clouds and the feedback from radio jets. In RX J0820.9+0752 intermediate-age stars are found in a filament outside the nucleus with no discernible star formation at the center of the galaxy. All projected galaxies consist of old stellar populations with deep D4000 breaks and lack detectable warm gas. While they may interact gravitationally with the central galaxy, they cannot have donated the upward of $10^{10}{M}_{\odot }$ of molecular gas found in these systems. These results highlight the importance of analyzing spatially resolved stellar kinematics and star formation histories in brightest cluster galaxies, an approach that remains relatively understudied.

21 pages, 14 figures, published in ApJ

References in corpus (26)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Heating Hot Atmospheres with Active Galactic Nuclei
• Non-linear Least Squares Fitting in IDL with MPFIT
• An Infrared Survey of Brightest Cluster Galaxies. II: Why are Some Brightest Cluster Galaxies Forming Stars?
• An Entropy Threshold for Strong H-alpha and Radio Emission in the Cores of Galaxy Clusters
• Star formation in a galactic outflow
• Quasar-Mode Feedback in Nearby Type 1 Quasars: Ubiquitous Kiloparsec-Scale Outflows and Correlations with Black Hole Properties
• Chemical enrichment in the cluster of galaxies Hydra A
• Formation of cold filaments in cooling flow clusters
• Simulating cosmic rays in clusters of galaxies - III. Non-thermal scaling relations and comparison to observations
• Ionized nebulae surrounding brightest cluster galaxies
• Ultraviolet Morphologies and Star-Formation Rates of CLASH Brightest Cluster Galaxies
• The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z=3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe
• Evidence for recent star formation in BCGs: a correspondence between blue cores and UV excess
• Filamentary Star Formation in NGC 1275
• Evolution of X-ray cavities
• Hot gaseous atmospheres in galaxy groups and clusters are both heated and cooled by X-ray cavities
• Cosmic ray confinement in fossil cluster bubbles
• Mass Distribution in Galaxy Cluster Cores
• A ${}^{13}$CO Detection in a Brightest Cluster Galaxy
• Feedback, scatter and structure in the core of the PKS 0745-191 galaxy cluster
• On the impact of spectral template uncertainties in synthetic stellar populations
• Radio jet-ISM interaction and positive radio-mechanical feedback in Abell 1795