| 1. |
- Hu, Zhensong, et al.
(författare)
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AMUSE-Antlia. I. Nuclear X-Ray Properties of Early-type Galaxies in a Dynamically Young Galaxy Cluster
- 2023
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 956:2
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Tidskriftsartikel (refereegranskat)abstract
- To understand the formation and growth of supermassive black holes (SMBHs) and their coevolution with host galaxies, it is essential to know the impact of environment on the activity of active galactic nuclei (AGNs). We present new Chandra X-ray observations of nuclear emission from member galaxies in the Antlia cluster, the nearest non-cool core and the nearest merging galaxy cluster, residing at D = 35.2 Mpc. Its inner region, centered on two dominant galaxies NGC 3268 and NGC 3258, has been mapped with three deep Chandra ACIS-I pointings. Nuclear X-ray sources are detected in 7/84 (8.3%) early-type galaxies (ETG) and 2/8 (25%) late-type galaxies with a median detection limit of 8 × 1038 erg s−1. All nuclear X-ray sources but one have a corresponding radio continuum source detected by MeerKAT at the L band. Nuclear X-ray sources detected in early-type galaxies are considered the genuine X-ray counterpart of low-luminosity AGN. When restricted to a detection limit of log ( L X / erg s − 1 ) ≥ 38.9 and a stellar mass of 10 ≤ log ( M ⋆ / M ⊙ ) < 11.6 , six of 11 ETGs are found to contain an X-ray AGN in Antlia, exceeding the AGN occupation fraction of 7/39 (18.0%) and 2/12 (16.7%) in the more relaxed, cool core clusters, Virgo and Fornax, respectively, and rivaling that of the AMUSE-Field ETG of 27/49 (55.1%). Furthermore, more than half of the X-ray AGN in Antlia is hosted by its younger subcluster, centered on NGC 3258. We believe that this is because SMBH activity is enhanced in a dynamically young cluster compared to relatively relaxed clusters.
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| 2. |
- Lee, Bumhyun, et al.
(författare)
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The Impact of the Group Environment on the Molecular Gas and Star Formation Activity
- 2021
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 17, s. 136-139
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- At least half of the local galaxies reside in galaxy groups, which indicates that the group is the common environment where galaxies evolve. Therefore, it is important to probe how significantly galaxies are affected by group environmental processes, in order to obtain a better understanding of galaxy evolution. We carried out a new CO imaging survey for 31 galaxies in the IC 1459 and NGC 4636 groups, using the Atacama Compact Array, to study the effect of the group environment on the molecular gas properties and the star formation activity. With our resolved CO data, combined with high-resolution H i images, we find asymmetric CO and H i distributions in the group galaxies. Compared to isolated galaxies, group members have relatively low molecular gas fraction and low star formation rate. These results suggest that the group environment can change the properties of cold gas components and star formation in group galaxies.
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