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Spiral structures and cold fronts in X-rays are frequently observed in cool core galaxy clusters. However, studies on radio mini-haloes associated with such spirals and their physical connections are rare. Here, we present the detection of an extended diffuse radio emission entrained in the X-ray spiral structure in a known cool core cluster Abell 795 (A795). Though the cool core is a sign of the relaxed nature of the clusters, our re-analysed 30 ks Chandra X-ray data of cluster A795 confirms the presence of an interesting log spiral structure of X-ray deficit region complemented by an X-ray excess counter spiral in the residual map, exposing its dynamical activity. Our new analysis of 150 $\&$ 325 MHz GMRT archival data of the cluster confirms the detection of a $\sim180$ kpc ultra-steep ($\alpha\sim-2.7$) diffuse radio structure which was previously reported as a candidate radio mini halo from low sensitive survey maps. This radio emission spans the entire spiral structure ($\sim186$ kpc), enclosed by two previously reported cold fronts. Furthermore, SDSS DR13 optical spectra, as well as GALEX's FUV data, show a considerably low total star formation rate of 2.52 M$_{\odot}$ yr$^{-1}$ and having no significant variation in metallicity distribution. We argued that the two-phase (hot and cold) plasma at the cluster core with differential velocity has probably caused the spiral formation and has redistributed the secondary electrons from the central BCG or the pre-accelerated electrons which have been (re-)accelerated by the sloshing turbulence to form the observed candidate radio mini-halo structure. This has been supported by a few previous studies that indicate spiral formation and sloshing turbulence may quench star formation and facilitate smooth metallicity distribution by mixing the gas in the core., Comment: 11 pages, 9 figures, Accepted for publication in MNRAS

This paper presents properties of the intracluster medium (ICM) in the environment of a cool core cluster Abell 2566 (redshift $z$ = 0.08247) based on the analysis of 20 ks Chandra X-ray data. 2D imaging analysis of the Chandra data from this cluster revealed spiral structures in the morphology of X-ray emission from within the central 109 kpc formed due to gas sloshing. This analysis also witness sharp edges in the surface brightness distribution along the south-east and north-west of the X-ray peaks at 41.6 kpc and 77.4 kpc, respectively. Spectral analysis of 0.5 - 7 keV X-ray photons along these discontinuities exhibited sharp temperature jumps from 2.3 to 3.1 keV and 1.8 to 2.8 keV, respectively, with consistency in the pressure profiles, implying their association with cold fronts due to gas sloshing of the gas. Further confirmation for such an association was provided by the deprojected broken power-law density function fit to the surface brightness distribution along these wedge shaped sectorial regions. This study also witness an offset of 4.6 arcsec (6.8 kpc) between the BCG and the X-ray peak, and interaction of the BCG with a sub-system in the central region, pointing towards the origin of the spiral structure due to a minor merger., Comment: 10 pages, 7 figures, Accepted for New Astronomy

This paper presents a comprehensive analysis of 30 ks Chandra and 46.8 ks (13 Hr) 1.4 GHz GMRT radio data on the cool-core cluster RXCJ0352.9+1941 with an objective to investigate AGN activities at its core. This study confirms a pair of X-ray cavities at projected distances of about 10.30 kpc and 20.80 kpc, respectively, on the NW and SE of the X-ray peak. GMRT L band (1.4 GHz) data revealed a bright radio source associated with the core of this cluster hosting multiple jet-like emissions. The spatial association of the X-ray cavities with the inner pair of radio jets confirm their origin due to AGN outbursts. The 1.4 GHz radio power ${\rm 7.4 \pm 0.8 \times 10^{39} \, erg\, s^{-1}}$ is correlated with the mechanical power stored in the X-ray cavities ($\sim7.90\times 10^{44}$ erg s$^{-1}$), implying that the power injected by radio jets in the ICM is sufficient enough to offset the radiative losses. The X-shaped morphology of diffuse radio emission seems to be comprised of two pairs of orthogonal radio jets, likely formed due to a spin-flip of jets due to the merger of two systems. The X-ray surface brightness analysis of the ICM in its environment revealed two non-uniform, extended spiral-like emission structures on either side of the core, pointing towards the sloshing of gas due to a minor merger and might have resulted in a cold front at $\sim$31 arcsec (62 kpc) with a temperature jump of 1.44 keV., Comment: 18 pages, 10 figures, Accepted for Journal of Astrophysics and Astronomy

High synchrotron energy peaked blazar 1ES 1959+650 is studied with Swift and XMM-Newton satellite in total 127 observations during the period June 2018-December 2020. We extensively studied its flux and spectral variability on intra-day and long-term timescales. Discrete correlation function analysis between soft and hard X-ray bands indicates soft as well as hard lags. The results are used to constrain the magnetic field of the emitting region which is found to be 0.64 (0.05) Gauss. On long-term timescales, distribution of fluxes shows lognormality behaviour which could be attributed to minijets-in-a-jet model or might be due to the propagation of relativistic shocks down the jet. The spectral energy distribution around the synchrotron peak is well described by the log parabola model. Spectral parameters like peak energy E$_{p}$, curvature $\beta$ and the peak luminosity L$_{p}$ are derived from spectral analysis. Their correlations are studied to constrain the acceleration processes of the emitting particles. E$_{p}$ shows strong correlation with L$_{p}$ during the high state of the source which indicates spectral changes might be caused by the variations of the average electron energy. Low values of curvature parameter $\beta$ and a weak correlation between E$_{p}$ and ${\beta}$ indicates co-existence of stochastic/statistical acceleration of electrons in the emitting region. Implications of other results are also discussed., Comment: 14 pages, 6 figures, Accepted for publication in ApJ

We report the results from analysis of six observations of Cygnus X-1 by Large Area X-ray Proportional Counters (LAXPC) and Soft X-ray Telescope (SXT) on-board AstroSat, when the source was in the hard spectral state as revealed by the broad band spectra. The spectra obtained from all the observations can be described by a single temperature Comptonizing region with disk and reflection components. The event mode data from LAXPC provides unprecedented energy dependent fractional root mean square (rms) and time-lag at different frequencies which we fit with empirical functions. We invoke a fluctuation propagation model for a simple geometry of a truncated disk with a hot inner region. Unlike other propagation models, the hard X-ray emission (> 4 keV) is assumed to be from the hot inner disk by a single temperature thermal Comptonization process. The fluctuations first cause a variation in the temperature of the truncated disk and then the temperature of the inner disk after a frequency dependent time delay. We find that the model can explain the energy dependent rms and time-lag at different frequencies., Comment: Accepted for Publication in MNRAS; 13 pages, 9 figures, Typos Corrected on Page 6

This paper reports a systematic search of X-ray cavities, density jumps and shocks in the inter-galactic environment of the galaxy group IC~1262 using {\it Chandra}, GMRT and VLA archival observations. The X-ray imaging analysis reveals a pair of X-ray cavities on the north and south of the X-ray peak, at projected distances of 6.48\,kpc and 6.30\,kpc respectively. Total mechanical power contained in both these cavities is found to be $\sim$12.37$\times 10^{42}$ erg~s$^{-1}$, and compares well with the X-ray luminosity, within the cooling radius, measured to be $\sim 3.29 \times 10^{42}$ erg~s$^{-1}$, suggesting that the mechanical power injected by the central AGN efficiently balances the radiative loss. We detect a previously unknown X-ray cavity at the position of southern radio lobe in the intra-group medium and find a loop of excess X-ray emission extending $\sim$100 kpc southwest from the central galaxy. The X-ray cavity at the position of southern radio lobe probably represents a first generation X-ray cavity. Two surface brightness edges are evident to the west and east$-$north of the center of this group. The radio galaxy at the core of the IC~1262 group is a rare low-redshift ultra-steep radio galaxy, its spectral index being $\alpha\! \sim\! -1.73$ (including the central AGN) and $\alpha\! \sim\! -2.08$ (excluding the central AGN). We detect a radio phoenix embedded within the southern radio lobe, for the first time in a poor group, with a spectral index ($\alpha \!\leq\! -1.92$). The spectral index distribution across the phoenix steepens with increasing distance from its intensity peak., Comment: 18 Pages, 12 Figures, Accepted for publication in APJ

We study the relationship between the UV and X-ray variability of the narrow-line Seyfert 1 galaxy 1H~0707-495. Using a year long {\it Swift} monitoring and four long {\it XMM-Newton} observations, we perform cross-correlation analyses of the UV and X-ray light curves, on both long and short time scales. We also perform time-resolved X-ray spectroscopy on 1-2 ks scale, and study the relationship between the UV emission and the X-ray spectral components - soft X-ray excess and a power-law. We find that the UV and X-ray variations anti-correlate on short, and possibly on long time scales as well. Our results rule out reprocessing as the dominant mechanism for the UV variability, as well as the inward propagating fluctuations in the accretion rate. Absence of a positive correlation between the photon index and the UV flux suggests that the observed UV emission is unlikely to be the seed photons for the thermal Comptonisation. We find a strong correlation between the continuum flux and the soft-excess temperature which implies that the soft excess is most likely the reprocessed X-ray emission in the inner accretion disc. Strong X-ray heating of the innermost regions in the disc, due to gravitational light bending, appears to be an important effect in 1H~0707-495, giving rise to a significant fraction of the soft excess as reprocessed thermal emission. We also find indications for a non-static, dynamic X-ray corona, where either the size or height (or both) vary with time., Comment: 10 pages, 7 figures, Accepted to MNRAS

Detection of the copious amount of X-ray emission from the dilute hot plasma in galaxy clusters suggests that a substantial fraction of the central intracluster medium (ICM) is cooling radiatively on a time scale much faster than the Hubble time. Theoretical models predict the cooling rate as high as about few hundred to few thousand solar mass per year, which would be then made available for the formation of new stars in the core of these clusters. However, systematic studies of the cores of such clusters failed to detect the expected reservoirs of cooled gas. Thus, the gas in the cores of galaxy clusters is losing substantial amount of energy in the form of X-rays but is not cooling. This in turn point towards the famous cooling flow paradox and hence demands some intermittent heating to balance the cooling over such a long period. Several sources have been suggested to counteract on the cooling of the ICM, however, the AGN feedback appeared to be the most promising and enough energetic source to resist cooling of the ICM in the cores of such clusters. In this presentation I will provide a brief overview on the feedback processes that are involved in the cores of the galaxy clusters with an emphasis on the AGN feedback and its observable signatures., Comment: National Conference on Signal Processing, Sustainable Energy Materials and Astronomy & Astrophysics (NSSEMA 2017)

We present a detailed analysis of a young merging galaxy cluster \mac~(z=0.43), from {\it Chandra} X-ray and {\it Hubble Space Telescope} archival data. X-ray observations confirm that the X-ray emitting intra-cluster medium (ICM) in this system is among the hottest (average $T=12.1 \pm 0.6$ keV) and most luminous known. Comparison of X-ray and optical images confirm that this system hosts two merging subclusters SC1 and SC2, separated by a projected distance of about 650\,kpc. The subcluster SC2 is newly identified in this work, while another subcluster (SC0), previously thought to be part of this merging system, is shown to be possibly a foreground object. Apart from two subclusters, we find a tail-like structure in the X-ray image, extending to a projected distance of $\sim$1\,Mpc, along the north-east direction of the eastern subcluster (SC1). From a surface brightness analysis, we detect two sharp surface brightness edges at $\sim$40$\arcsec$ ($\sim$320\,kpc) and $\sim$80$\arcsec$ ($\sim$640\,kpc) to the east of SC1. The inner edge appears to be associated with a merger-driven cold front, while the outer one is likely to be due to a shock front, the presence of which, ahead of the cold front, makes this dynamically disturbed cluster interesting. Nearly all the early-type galaxies belonging to the two subclusters, including their BCGs, are part of a well-defined red sequence., Comment: 13 pages, 12 figures, 6 Tables, Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

We report the results of our radio, optical and infra-red studies of a peculiar radio source 4C~35.06, an extended radio-loud AGN at the center of galaxy cluster Abell 407 ($z=0.047$). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of $\sim$1~arcmin size. This system (named the `Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C~35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400~kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few$\,\times (10^7 - 10^8)$ yr. Such ultra-steep spectrum relic radio lobes without definitive hot-spots are rare, and they provide an opportunity to understand the life-cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of the growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology., Comment: Published in MNRAS | No. of pages 12, 10 figures and 4 tables. Comments are welcome

We report the multiband imagery with an emphasis on the X-ray emission properties of a prominent dust lane lenticular galaxy NGC 5866. X-ray emission from this galaxy is due to a diffuse component and a substantial contribution from the population of discrete X-ray binary sources. A total of 22 discrete sources have been detected within the optical D25 extent of the galaxy, few of which exhibit spatial association with the globular clusters hosted by this system. Composite spectrum of the diffuse emission from this galaxy was well constrained by a thermal plasma model plus a power law component to represent the emission from unresolved sources, while that of the discrete sources was well fitted by an absorbed power law component of photon index 1.82$\pm$0.14. X-ray color-color plot for the resolved source was used to classify the detected sources. The cumulative X-ray luminosity function of the XRBs is well represented by a power law function of index of {\Gamma} ~ 0.82$\pm$0.12. Optical imagery of NGC 5866 revealed a prominent dust lane along the optical major axis of the host with dust extinction properties similar to those of the canonical grains in the Milky Way. The dust grains responsible for the extinction of starlight in NGC 5866 are relatively smaller in size when compared with the canonical grains in the Milky Way and high energetic charged particles seems to be responsible for the modulation of the dust grain size. Spatial correspondence is evident between the dust and other phases of ISM., Comment: 14 pages, 10 figures, accepted for publication in Asian Journal of Physics (AJP) Vol 24, No 8, 2015 (special issue)

We present results based on the systematic analysis of high resolution 95 ks Chandra observations of the strong cool core cluster Abell 2390 at the redshift of z= 0.228 that hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the atmosphere of Abell 2390 within central 30". Presence of these cavities have been confirmed through a variety of image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in the NW direction is cooler than that on the SE direction. Temperature jump in all directions is evident near 25" (90.5 kpc) corresponding to the average Mach number 1.44$\pm$0.05, while another jump from 7.47 keV to 9.10 keV at 68" (246 kpc) in the north-west direction, corresponding to Mach number 1.22$\pm$0.06 and these jumps are associated with the cold fronts. Tricolour map as well as hardness ratio map detects cool gas clumps in the central 30 kpc region of temperature $4.45_{-0.10}^{+0.16}$ keV. The entropy profile derived from the X-ray analysis is found to fall systematically inward in a power-law fashion and exhibits a floor near 12.20$\pm$2.54 keV cm$^2$ in the central region. This flattening of the entropy profile in the core region confirms the intermittent heating at the centre by AGN. The diffuse radio emission map at 1.4\,GHz using VLA L-band data exhibits highly asymmetric morphology with an edge in the north-west direction coinciding with the X-ray edge seen in the unsharp mask image., Comment: 22 pages, 13 figures, accepted for publication in Ap&SS

We present results based on the systematic analysis of \textit{Chandra} archive data on the X-ray bright Abell Richness class-I type cluster Abell 1991 with an objective to investigate properties of the X-ray cavities hosted by this system. The unsharp masked image as well as 2-d $\beta$ model subtracted residual image of Abell 1991 reveals a pair of X-ray cavities and a region of excess emission in the central $\sim$12 kpc region. Both the cavities are of ellipsoidal shape and exhibit an order of magnitude deficiency in the X-ray surface brightness compared to that in the undisturbed regions. Spectral analysis of X-ray photons extracted from the cavities lead to the temperature values equal to $1.77_{-0.12}^{+0.19}$ keV for N-cavity and $1.53_{-0.06}^{+0.05}$ keV for S-cavity, while that for the excess X-ray emission region is found to be equal to $2.06_{-0.07}^{+0.12}$ keV. Radial temperature profile derived for Abell 1991 reveals a positive temperature gradient, reaching to a maximum of 2.63 keV at $\sim$ 76 kpc and then declines in outward direction. 0.5$-$2.0 keV soft band image of the central 15\arcsec region of Abell 1991 reveals relatively cooler three different knot like features that are about 10\arcsec off the X-ray peak of the cluster. Total power of the cavities is found to be equal to $\sim 8.64\times 10^{43}$ \lum, while the X-ray luminosity within the cooling radius is found to be 6.04 $\times 10^{43}$ \lum, comparison of which imply that the mechanical energy released by the central AGN outburst is sufficient to balance the radiative loss., Comment: 29 pages, 12 figures and 3 tables, accepted for publication in Astrophysics and Space Science

We present an X-ray study of the nuclear and extended emission of a nearby Fanaroff & Riley class I (FR-I) radio galaxy CTD 86 based on the \xmm{} observations. Two different components observed are : diffuse thermal emission from hot gas ($kT\sim 0.79\kev$, $n_e\sim 10^{-3}{\rm cm^{-3}}$, $L_X \sim 5\times10^{42}{\rm erg s^{-1}}$ extended over $\sim 186{\rm kpc}$), and unresolved nuclear emission exhibiting mild activity. The hot gaseous environment of CTD 86 is similar to that found in groups of galaxies or in bright early-type galaxies. No clear signatures of radio-lobe interaction with the diffuse hot gas is evident in this case. X-ray emission from the nucleus is well constrained by an intrinsically absorbed ($N_H \sim 5.9\times10^{22}{\rm cm^{-2}}$) power law ($\Gamma \sim 1.5$) with $2-10\kev$ luminosity $L_X \sim 2.1\times10^{42}{\rm erg s^{-1}}$. We have measured the stellar velocity dispersion, $\sigma=182\pm8\kms$, for the CTD 86 and estimated a mass $M_{BH}\sim 9\times 10^7{\rm M_\odot}$ with $L_{bol}/L_{Edd} \sim 4\times10^{-3}$. The low $L_{bol}/L_{Edd}$ rate and high $L_X/L_{[O III]}$ ratio suggest that the central engine of CTD 86 consists of a truncated accretion disk lacking a strong ionizing UV radiation and an inner hot flow producing the X-ray emission. The truncated disk is likely to be inclined with ($i\sim40^\circ-50^\circ$) such that our line of sight passes through the outer regions of a putative torus and thus results in high X-ray absorption. We have also identified two bright X-ray sources, SDSS J142452.11+263715.1 and SDSS J142443.78+263616.2, near CTD 86. SDSS J142452.11+263715.1 is a type 1 active galactic nucleus at $z=0.3761$ and unabsorbed $0.3-10\kev$ X-ray luminosity $L_X\sim 8 \times 10^{43}{\rm erg s^{-1}}$, while SDSS J142443.78+263616.2 is probably a galaxy with an active nucleus., Comment: 19 pages, 3 Tables, 9 figures, Accepted for publication in MNRAS

We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the content of dust and its association with the other phases of the ISM. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e., in the inner part it exists in the form of a prominent lane while at about 6--7\,kpc it apparently takes an arc-like pattern extended along the North-East direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. Dust emission mapped using \textit{Spitzer} data at 8 $\mu$m indicates even more complex morphological structures of the dust in NGC1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve suggesting similar properties of the dust grains. The dust content of NGC 1316 estimated from optical extinction is $\sim$ 2.13$\times\, 10^5$ \Msun. This is a lower limit compared to that estimated using the IRAS flux densities $\sim$ 5.17$\times\, 10^6$ \Msun\, and flux densities at 24$\mu$m, 70$\mu$m and 160 $\mu$m from MIPS $\sim$ 3.2$\times\, 10^7$ \Msun. High resolution \textit{Chandra} observations of this merger remnant system have provided with an unprecedented view of the complex nature of hot gas distribution in NGC 1316 which closely matches the morphology of ionized gas and to some extent with the dust also. X-ray color-color plot for the resolved sources within optical D$_{25}$ extent of NGC 1316 has enabled us to separate them in different classes., Comment: 17 pages, 8 figures, Accepted for publication in the RAA

We present spectral properties of a total of 996 discrete X-ray sources resolved in a sample of 23 dusty early-type galaxies selected from different environments. The combined X-ray luminosity function of all the 996 sources within the optical \D of the sample galaxies is well described by a broken power law with a break at 2.71$\times$\te \lum and is close to the Eddington limit for a 1.4\Msun neutron star. Out of the 996, about 63\p of the sources have their X-ray luminosities in the range between few\tim\ts to 2.0 \tim \tn \lum and are like normal LMXBs; about 15-20\p with luminosities $<$ few \tim 10$^{37}$ \lum are either super-soft or very-soft sources; while the remainder represents ULXs, HMXBs or unrelated heavily absorbed harder sources. More XRBs have been detected in the galaxies from isolated regions while those from rich groups and clusters host very few sources. The X-ray color-color plot for these sources has enabled us to classify them as SNRs, LMXBs, HMXBs and heavily absorbed AGNs. The composite X-ray spectra of the resolved sources within \D region of each of the galaxies are best represented by a power law with the average photon spectral index close to 1.65. The contribution of the resolved sources to the total X-ray luminosity of their host is found to vary greatly, in the sense that, in galaxies like NGC 3379 the XRB contribution is about 81\p while for NGC 5846 it is only 2\p. A correlation has been evidenced between the cumulative X-ray luminosity of the resolved sources against the star formation rate and the Ks band luminosity of the target galaxies indicating their primordial origin., Comment: 15 Pages, 6 Figures & 2 Tables, Accepted for publication in New Astronomy

We present the results based on multiwavelength imaging observations of the prominent dust lane starburst galaxy NGC 1482 aimed to investigate the extinction properties of dust existing in the extreme environment. (B-V) colour-index map derived for the starburst galaxy NGC 1482 confirms two prominent dust lanes running along its optical major axis and are found to extend up to \sim 11 kpc. In addition to the main lanes, several filamentary structures of dust originating from the central starburst are also evident. Though, the dust is surrounded by exotic environment, the average extinction curve derived for this target galaxy is compatible with the Galactic curve, with RV =3.05, and imply that the dust grains responsible for the optical extinction in the target galaxy are not really different than the canonical grains in the Milky Way. Our estimate of total dust content of NGC 1482 assuming screening effect of dust is \sim 2.7 \times 10^5 Msun, and provide lower limit due to the fact that our method is not sensitive to the intermix component of dust. Comparison of the observed dust in the galaxy with that supplied by the SNe to the ISM, imply that this supply is not sufficient to account for the observed dust and hence point towards the origin of dust in this galaxy through a merger like event. Our multiband imaging analysis reveals a qualitative physical correspondence between the morphologies of the dust and H{\alpha} emission lines as well as diffuse X-ray emission in this galaxy. continue.... for more detail please see in pdf file., Comment: 22 pages, 11 Figures. Accepted for publication in New Astronomy

We present results based on the systematic analysis of currently available Chandra archive data on the brightest galaxy in the Draco constellation NGC 6338, in order to investigate the properties of the X-ray cavities. In the central ~6 kpc, at least a two and possibly three, X-ray cavities are evident. All these cavities are roughly of ellipsoidal shapes and show a decrement in the surface brightness of several tens of percent. In addition to these cavities, a set of X-ray bright filaments are also noticed which are spatially coincident with the H{\alpha} filaments over an extent of 15 kpc. The H{\alpha} emission line filaments are perpendicular to the X- ray cavities. Spectroscopic analysis of the hot gas in the filaments and cavities reveal that the X-ray filaments are cooler than the gas contained in the cavities. The emission line ratios and the extended, asymmetric nature of the H{\alpha} emission line filaments seen in this system require a harder ionizing source than that produced by star formation and/or young, massive stars. Radio emission maps derived from the analysis of 1.4 GHz VLA FIRST survey data failed to show any association of these X-ray cavities with radio jets, however, the cavities are filled by radio emission. The total power of the cavities is 17\times 1042 erg s-1 and the ratio of the radio luminosity to cavity power is ~ 10-4, implying that most of the jet power is mechanical., Comment: The paper contains 12 figures and 3 tables, Accepted 2011 December 7 for publication in MNRAS

We present results of morphological and spectroscopic study of hot gas in some early-type galaxies based on the analysis of high resolution X-ray images acquired from the archive of Chandra space mission. Distribution of the hot gas in target galaxies after eliminating contribution from the discrete sources (LMXBs) displays varied morphologies, ranging from very compact nuclear emission to very extensive emission, larger than even optical images of the host galaxies. The surface brightness profile of the hot gas in program galaxies is well described by a single beta model, while spectrum of the diffuse emission is best fitted by a combined soft MEKAL model and a hard power law model. We use these results to derive temperature and abundance profiles of the hot gas in host galaxies. The deprojection of the diffuse emission shows a temperature gradient in some of the galaxies. We also report on the 2-D distribution of the discrete sources (LMXBs) in host galaxies and compare it with their optical morphologies. The X-ray spectrum of the resolved sources is well-fit by a hard power law model with X-ray luminosities (0.3 to 10 keV) in the range from 5$\times$ 10$^{37}$ to 2.5$\times$ 10$^{39}$ erg s$^{-1}$. X-ray luminosity function (XLF) of the LMXBs shows a break near the luminosity comparable to the Eddington luminosity for a 1.4 M$_\odot$ neutron star., Comment: 3 pages, 4 figures, presented in the XXVIIth ASI meeting

In this paper we present extinction properties of interstellar dust in a prominent dust lane galaxy NGC 4370 based on the optical broad band (BVRI) imaging observations taken from the Himalaya Chandra Telescope (HCT), Hanle and the near-IR (J,H,K$_s$) images taken from the 2MASS archive. NGC 4370 belongs to the Virgo cluster (VCC 0758) and form a non-interactive pair with NGC 4365 at 10$\arcmin$. NGC 4370 hosts a prominent dust lane running parallel to its optical major axis and is extended almost up to 1\arcmin. The extinction curve derived for NGC 4370 is found to run parallel to Galactic extinction curve, implying that the properties of dust in NGC 4370 are identical to those of the canonical grains in the Milky Way. The $R_V$ value is found to be equal to 2.85$\pm$0.05 and is consitent with the values reported for the dust lane galaxies. The total dust content of NGC 4370 estimated using optical extinction and IRAS flux densities are found to be equal to $4.4\times 10^4$ \msol and $2.0\times 10^5$ \msol, respectively. As regard to the origin of dust and ISM in this galaxy, the accumulated dust by this galaxy over its life-time is insufficient to account for the detected mass by optical means, which in turn imply that the ISM might have been acquired by the NGC 4370 through a merger like event. An attempt is also made to study the apparent spatial correspondence between the multiple phases of ISM, i.e., hot gas, warm gas and dust in this galaxy by obtaining optical emission maps from narrow band imaging and diffuse X-ray emission map obtained from the analysis of \emph{Chandra} archival data. This analysis implies a physical connection between the dust and warm gas in terms of their physical co-existence and common origin too., Comment: 8 pages, 9 figures

We report optical extinction properties of dust for a sample of 26 early-type galaxies based on the analysis of their multicolour CCD observations. The wavelength dependence of dust extinction for these galaxies is determined and the extinction curves are found to run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic environment are quite similar to those of the Milky Way. For the sample galaxies, value of the parameter $R_V$, the ratio of total extinction in $V$ band to selective extinction in $B$ & $V$ bands, lies in the range 2.03 - 3.46 with an average of 3.02, compared to its canonical value of 3.1 for the Milky Way. A dependence of $R_V$ on dust morphology of the host galaxy is also noticed in the sense that galaxies with a well defined dust lane show tendency to have smaller $R_V$ values compared to the galaxies with disturbed dust morphology. The dust content of these galaxies estimated using total optical extinction is found to lie in the range $10^4$ to $10^6 \rm M_{\sun}$, an order of magnitude smaller than those derived from IRAS flux densities, indicating that a significant fraction of dust intermixed with stars remains undetected by the optical method. We examine the relationship between dust mass derived from IRAS flux and the X-ray luminosity of the host galaxies.The issue of the origin of dust in early-type galaxies is also discussed., Comment: 12 pages, 6 figures. Accepted for publication in Astronomy & Astrophysics