Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userExploring X-ray Binary Populations in Compact Group Galaxies with $Chandra$
96
0
0.0
(
0
)
Added by
Panayiotis Tzanavaris
Publication date
2015
fields
Physics
and research's language is
English
Authors
P. Tzanavaris
Ask ChatGPT about the research
No Arabic abstract
We obtain total galaxy X-ray luminosities, $L_X$, originating from individually detected point sources in a sample of 47 galaxies in 15 compact groups of galaxies (CGs). For the great majority of our galaxies, we find that the detected point sources most likely are local to their associated galaxy, and are thus extragalactic X-ray binaries (XRBs) or nuclear active galactic nuclei (AGNs). For spiral and irregular galaxies, we find that, after accounting for AGNs and nuclear sources, most CG galaxies are either within the $pm1sigma$ scatter of the Mineo et al. (2012) $L_X$ - star formation rate (SFR) correlation or have higher $L_X$ than predicted by this correlation for their SFR. We discuss how these excesses may be due to low metallicities and high interaction levels. For elliptical and S0 galaxies, after accounting for AGNs and nuclear sources, most CG galaxies are consistent with the Boroson et al. (2011) $L_X$ - stellar mass correlation for low-mass XRBs, with larger scatter, likely due to residual effects such as AGN activity or hot gas. Assuming non-nuclear sources are low- or high-mass XRBs, we use appropriate XRB luminosity functions to estimate the probability that stochastic effects can lead to such extreme $L_X$ values. We find that, although stochastic effects do not in general appear to be important, for some galaxies there is a significant probability that high $L_X$ values can be observed due to strong XRB variability.
rate research
Read More
Chandras high angular resolution can resolve emission from stellar X-ray binaries out of the diffuse X-ray emission from gaseous atmospheres within elliptical galaxies. Variations in the X-ray binary populations (per unit galaxian optical luminosity) are correlated with variations in the specific frequency of globular clusters in ellipticals. This indicates that X-ray binaries are largely formed in globular clusters, rather than being a primordial field population.
We present the results of a search for galaxy clusters and groups in the $sim2$ square degree of the COSMOS field using all available X-ray observations from the XMM-Newton and Chandra observatories. We reach an X-ray flux limit of $3times10^{-16};ergs;cm^{-2};s^{-1}$ in 0.5--2 keV range, and identify 247 X-ray groups with $M_{200c}=8times10^{12}-3times10^{14};M_{odot}$ at a redshift range of $0.08leq z<1.53$, using the multiband photometric redshift and the master spectroscopic redshift catalogues of the COSMOS. The X-ray centres of groups are determined using high-resolution Chandra imaging. We investigate the relations between the offset of the brightest group galaxies (BGGs) from halo X-ray centre and group properties and compare with predictions from semi-analytic models and hydrodynamical simulations. We find that BGG offset decreases with both increasing halo mass and decreasing redshift with no strong dependence on the X-ray flux and SNR. We show that the BGG offset decreases as a function of increasing magnitude gap with no considerable redshift dependent trend. The stellar mass of BGGs in observations extends over a wider dynamic range compared to model predictions. At $z<0.5$, the central dominant BGGs become more massive than those with large offsets by up to 0.3dex, in agreement with model prediction. The observed and predicted lognormal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is $sim0.3$dex.
We study the coherence of the near-infrared and X-ray background fluctuations and the X-ray spectral properties of the sources producing it. We use data from multiple Spitzer and Chandra surveys, including the UDS/SXDF surveys, the Hubble Deep Field North, the EGS/AEGIS field, the Chandra Deep Field South and the COSMOS surveys, comprising $sim$2275 Spitzer/IRAC hours and $sim$~16 Ms of Chandra data collected over a total area of $sim$~1~deg$^2$. We report an overall $sim$5$sigma$ detection of a cross-power signal on large angular scales $>$ 20$$ between the 3.6 and 4.5mum and the X-ray bands, with the IR vs [1-2] keV signal detected at 5.2$sigma$. The [0.5-1] and [2-4] keV bands are correlated with the infrared wavelengths at a $sim$1$-$3$sigma$ significance level. The hardest X-ray band ([4-7] keV) alone is not significantly correlated with any infrared wavelengths due to poor photon and sampling statistics. We study the X-ray SED of the cross-power signal. We find that its shape is consistent with a variety of source populations of accreting compact objects, such as local unabsorbed AGNs or high-z absorbed sources. We cannot exclude that the excess fluctuations are produced by more than one population. Because of poor statistics, the current relatively broad photometric bands employed here do not allow distinguishing the exact nature of these compact objects or if a fraction of the fluctuations have instead a local origin.
We report the discovery of a very diverse set of five low-surface brightness (LSB) dwarf galaxy candidates in Hickson Compact Group 90 (HCG 90) detected in deep U- and I-band images obtained with VLT/VIMOS. These are the first LSB dwarf galaxy candidates found in a compact group of galaxies. We measure spheroid half-light radii in the range $0.7!lesssim! r_{rm eff}/{rm kpc}! lesssim! 1.5$ with luminosities of $-11.65!lesssim! M_U! lesssim! -9.42$ and $-12.79!lesssim! M_I! lesssim! -10.58$ mag, corresponding to a color range of $(U!-!I)_0!simeq!1.1!-!2.2$ mag and surface brightness levels of $mu_U!simeq!28.1,{rm mag/arcsec^2}$ and $mu_I!simeq!27.4,{rm mag/arcsec^2}$. Their colours and luminosities are consistent with a diverse set of stellar population properties. Assuming solar and 0.02 Z$_odot$ metallicities we obtain stellar masses in the range $M_*|_{Z_odot} simeq 10^{5.7-6.3} M_{odot}$ and $M_*|_{0.02,Z_odot}!simeq!10^{6.3-8},M_{odot}$. Three dwarfs are older than 1 Gyr, while the other two significantly bluer dwarfs are younger than $sim 2$ Gyr at any mass/metallicity combination. Altogether, the new LSB dwarf galaxy candidates share properties with dwarf galaxies found throughout the Local Volume and in nearby galaxy clusters such as Fornax. We find a pair of candidates with $sim!2$ kpc projected separation, which may represent one of the closest dwarf galaxy pairs found. We also find a nucleated dwarf candidate, with a nucleus size of $r_{rm eff}!simeq!46!-!63$ pc and magnitude M$_{U,0}=-7.42$ mag and $(U!-!I)_0!=!1.51$ mag, which is consistent with a nuclear stellar disc with a stellar mass in the range $10^{4.9-6.5},M_odot$.
We propose a physically motivated and self-consistent prescription for the modeling of transient neutron star (NS) low-mass X-ray binary (LMXB) properties, such as duty cycle (DC), outburst duration and recurrence time. We apply this prescription to the population synthesis (PS) models of field LMXBs presented by Fragos et al. (2008), and compare the transient LMXB population to the Chandra X-ray survey of the two elliptical galaxies NGC 3379 and NGC 4278, which revealed several transient sources (Brassington et al., 2008, 2009). We are able to exclude models with a constant DC for all transient systems, while models with a variable DC based on the properties of each system are consistent with the observed transient populations. We predict that the majority of the observed transient sources in these two galaxies are LMXBs with red giant donors. Our comparison suggests that LMXBs formed through evolution of primordial field binaries are dominant in globular cluster (GC) poor elliptical galaxies, while they still have a significant contribution in GC rich ones.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
