Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMetallicity of the Fossil Group NGC 1550 Observed with Suzaku
201
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We studied the temperature and metal abundance distributions of the intra-cluster medium (ICM) in a group of galaxies NGC 1550 observed with Suzaku. The NGC 1550 is classified as a fossil group, which have few bright member galaxies except for the central galaxy. Thus, such a type of galaxy is important to investigate how the metals are enriched to the ICM. With the Suzaku XIS instruments, we directly measured not only Si, S, and Fe lines but also O and Mg lines and obtained those abundances to an outer region of ~0.5 r_180 for the first time, and confirmed that the metals in the ICM of such a fossil group are indeed extending to a large radius. We found steeper gradients for Mg, Si, S, and Fe abundances, while O showed almost flat abundance distribution. Abundance ratios of alpha-elements to Fe were similar to those of the other groups and poor clusters. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 2.9 +- 0.5 within 0.1 r_180, and the value was consistent with those for the other groups and poor clusters observed with Suzaku. We also calculated metal mass-to-light ratios (MLRs) for Fe, O and Mg with B-band and K-band luminosities of the member galaxies of NGC 1550. The derived MLRs were comparable to those of NGC 5044 group in the r<0.1 r_180 region, while those of NGC 1550 are slightly higher than those of NGC 5044 in the outer region.
rate research
Read More
We present a new insight on NGC 6034 and UGC 842, two groups of galaxies previously reported in the literature as being fossil groups. The study is based on optical photometry and spectroscopy obtained with the CTIO Blanco telescope and Sloan Digital Sky Survey archival data. We find that NGC 6034 is embedded in a large structure, dominated by three rich clusters and other small groups. Its first and next four ranked galaxies have magnitude differences in the r band and projected distances which violate the optical criteria to classify it as a fossil group. We confirm that the UGC 842 group is a fossil group, but with about half the velocity dispersion that is reported in previous works. The velocity distribution of its galaxies reveals the existence of two structures in its line of sight, one with sigmaV ~ 223 km/s and another with sigmaV ~ 235 km/s, with a difference in velocity of ~820 km/s. The main structure is dominated by passive galaxies, while these represent ~60% of the second structure. The X-ray temperature for the intragroup medium of a group with such a velocity dispersion is expected to be kT ~0.5-1 keV, against the observed value of kT ~1.9 keV reported in the literature. This result makes UGC 842 a special case among fossil groups because (1) it represents more likely the interaction between two small groups, which warms the intragroup medium and/or (2) it could constitute evidence that member galaxies lost energy in the process of spiraling toward the group center, and decreased the velocity dispersion of the system. As far as we know, UGC 842 is the first low-mass fossil group studied in detail.
The Suzaku X-ray satellite observed the nearby spiral galaxy NGC 4258 for a total good exposure time of 100 ks. We present an analysis of the Suzaku XIS data, in which we confirm that the 0.5--2 keV spectra of the interstellar medium (ISM) are well-represented by a two-temperature model. The cool and hot ISM temperatures are 0.23+-0.02 and 0.59 +-0.01 keV, respectively. Suzakus excellent spectral sensitivity enables us to measure the metal abundances of O, Ne, Mg, Si and Fe of the ISM for the first time. The resultant abundance pattern of O, Mg, Si, and Fe is consistent with that of the new solar abundance table of Lodders (2003), rather than Anders & Grevesse (1989). This suggests that the metal enrichment processes of NGC 4258 and of our Galaxy are similar.
Fossil groups are considered the end product in a galaxy groups evolution -- a massive central galaxy that dominates the luminosity budget of the group, as the outcome of efficient merging between intermediate-luminosity members. Little is however known about the faint satellite systems of fossil groups. Here we present a SUBARU/Suprime-Cam wide-field, deep imaging study in the B- and R-band of the nearest fossil group NGC 6482 (M_{tot}sim4times10^{12}M_{sun}), covering the virial radius out to 310 kpc. We perform detailed completeness estimations and select group member candidates by a combination of automated object detection and visual inspection. A fiducial sample of 48 member candidates down to M_R -10.5 mag is detected, making this study the deepest of a fossil group up to now. We investigate the photometric scaling relations, the colour-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The colour-magnitude relation is comparable to that of nearby galaxy clusters, and exhibits significant scatter at the faintest luminosities. The completeness-corrected luminosity function is dominated by early-type dwarfs and is characterized by a faint end slope alpha=-1.32pm0.05. We conclude that the NGC 6482 fossil group shows photometric properties consistent with those of regular galaxy clusters and groups, including a normal abundance of faint satellites.
We have analyzed the Chandra archival data of NGC 1132, a well-known fossil group, i.e. a system expected to be old and relaxed long after the giant elliptical galaxy assembly. Instead, the Chandra data reveal that the hot gas morphology is disturbed and asymmetrical, with a cold front following a possible bow shock. We discuss possible origins of the disturbed hot halo, including sloshing by a nearby object, merger, ram pressure by external hotter gas and nuclear outburst. We consider that the first two mechanisms are likely explanations for the disturbed hot halo, with a slight preference for a minor merger with a low impact parameter because of the match with simulations and previous optical observations. In this case, NGC 1132 may be a rare example of unusual late mergers seen in recent simulations. Regardless of the origin of the disturbed hot halo, the paradigm of the fossil system needs to be reconsidered.
The metallicity distribution in the intracluster medium of the NGC 5044 group was studied up to 0.3 r_180 using the XIS instrument on board the Suzaku satellite. Abundances of O, Mg, Si, S, and Fe were measured with high accuracy. The region within a radius of 0.05 r_180 from the center shows approximately solar abundances of Mg, Si, S, and Fe, while the O/Fe ratio is about 0.5--0.6 in solar units. In the outer region, the Fe abundance gradually drops to 0.3 solar. Radial abundance profiles of Mg, Si and S are similar to that of Fe, while that of O seems to be flatter. At r>0.05 r_180, the mass density profile of O differs from that of Fe, showing a shoulder-like structure that traces the luminosity density profile of galaxies. The mass-to-light ratios for O and Fe in NGC 5044 are one of the largest among groups of galaxies, but they are still smaller than those in rich clusters. These abundance features probably reflect the metal enrichment history of this relaxed group hosting a giant elliptical galaxy in the center.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
