Sudhanshu Barway

Possible detection of two giant extrasolar planets orbiting the eclipsing polar UZ Fornacis

We present new high-speed, multi-observatory, multi-instrument photometry of the eclipsing polar UZ For in order to measure precise mid-eclipse times with the aim of detecting any orbital period variations. When combined with published eclipse times and archival data spanning ∼27 years, we detect departures from a linear and quadratic trend of ∼60 s. The departures are strongly suggestive of two cyclic variations of 16(3) and 5.25(25) years. The two favoured mechanisms to drive the periodicities are either two giant extrasolar planets as companions to the binary [with minimum masses of 6.3(1.5) and 7.7(1.2)MJup) or a magnetic cycle mechanism (e.g. Applegate’s mechanism) of the secondary star. Applegate’s mechanism would require the entire radiant energy output of the secondary and would therefore seem to be the least likely of the two, barring any further refinements in the effect of magnetic fields (e.g. those of Lanza et al.). The two-planet model can provide realistic solutions but it does not quite capture all of the eclipse times measurements. A highly eccentric orbit for the outer planet would fit the data nicely, but we find that such a solution would be unstable. It is also possible that the periodicities are driven by some combination of both mechanisms. Further observations of this system are encouraged.

Near-infrared bulge-disc correlations of lenticular galaxies

We consider the luminosity and environmental dependence of structural parameters of lenticular galaxies in the near-infrared K band. Using a 2D galaxy image decomposition technique, we extract bulge and disc structural parameters for a sample of 36 lenticular galaxies observed by us in the K band. By combining data from the literature for field and cluster lenticulars with our data, we study correlations between parameters that characterize the bulge and the disc as a function of luminosity and environment. We find that scaling relations such as the Kormendy relation, photometric plane and other correlations involving bulge and disc parameters show a luminosity dependence. This dependence can be explained in terms of galaxy formation models in which faint lenticulars (MT > −24.5) formed via secular formation processes that likely formed the pseudo-bulges of late-type disc galaxies, while brighter lenticulars (MT < −24.5) formed through a different formation mechanism most likely involving major mergers. On probing variations in lenticular properties as a function of environment, we find that faint cluster lenticulars show systematic differences with respect to faint field lenticulars. These differences support the idea that the bulge and disc components fade after the galaxy falls into a cluster, while simultaneously undergoing a transformation from spiral to lenticular morphologies.

Lenticular galaxy formation: possible luminosity dependence

We investigate the correlation between the bulge effective radius (re) and disk scale length (rd) in the near-infrared K band for lenticular galaxies in the field and in clusters. We find markedly different relations between the two parameters as a function of luminosity. Lenticulars with total absolute magnitude fainter than MT = -24.5 show a positive correlation, in line with predictions of secular formation processes for the pseudobulges of late-type disk galaxies. But brighter lenticulars with MT < -24.5 show an anticorrelation, indicating that they formed through a different mechanism. The available data are insufficient to reliably determine the effect of galaxy environment on these correlations.

A supermassive black hole fundamental plane for ellipticals

We obtain the coefficients of a new fundamental plane for supermassive black holes at the centers of elliptical galaxies, involving measured central black hole mass and photometric parameters that define the light distribution. The galaxies are tightly distributed around this mass fundamental plane, with improvement in the rms residual over those obtained from the MBH-σ and MBH-L relations. This implies a strong multidimensional link between central massive black hole formation and global photometric properties of elliptical galaxies, and provides an improved estimate of black hole mass from galaxy data.

Luminosity-dependent star formation history of S0 galaxies: evidence from GALEX–SDSS–2MASS–WISE colours

We combine UV/Optical/near-IR/mid-IR data on a sample of ∼240 S0 galaxies to examine various star formation related processes in them. We split the sample into bright and faint S0 galaxies based on their K band luminosity. Comparing the FUVNUV versus NUV-K color-color diagram with a Simple Stellar Population (SSP) model shows that ellipticals and bright S0 galaxies are dominated by a stellar population of age > 10 years while faint S0 galaxies may contain stars as young as 10 years, providing evidence for relatively recent star formation activity. The strength of the 4000 Å break is also systematically higher in brighter S0 galaxies, again indicating the presence of an old stellar population. Their mid-IR colours indicate that bright S0 colours are like those of ellipticals while faint S0 colours are more like spirals. All these observations are consistent with a scenario in which low-luminosity S0 galaxies likely formed by the stripping of gas from the discs of late-type spiral galaxies, which in turn formed their pseudo bulges through secular evolution processes, possibly involving multiple episodes of star formation. On the other hand, more luminous S0 galaxies likely formed the bulk of their stars at early epochs, similar to the star formation in elliptical galaxies, and are characterised by an old coeval stellar population and classical bulges.

Photometric Scaling Relations for Bulges of Galaxies

We describe the photometric parameters of the bulges of galaxies of different Hubble types including ellipticals, lenticulars, early and late type spirals and early type dwarf galaxies. Analyzing the distributions of various photometric parameters and two- and three-dimensional correlations between them, we find that there is a difference in the correlations exhibited by bright (

Unravelling the morphologies of Luminous Compact Galaxies using the HST/ACS GOODS survey

M_{\rm K} < -22

A SPITZER STUDY OF PSEUDOBULGES IN S0 GALAXIES: SECULAR EVOLUTION OF DISKS

) and faint bulges, irrespective of their Hubble type. Importantly, the bright bulges, which include typically E/S0 galaxies and bulges of early type spirals, are tightly distributed around a common photometric plane (PP), while their fainter counterparts, mainly bulges of late type spirals and dwarf galaxies show significant deviation from the planar distribution. We show that the specific entropy, determined from the bulge structural parameters, systematically increases as we move from late to early Hubble types. We interpret this as evidence for hierarchical merging and passive evolution scenarios for bright and faint bulges respectively.

Dust and ionized gas association in E/S0 galaxies with dust lanes: clues to their origin

Context. Luminous Compact Galaxies (LCGs) (M B 15 A) constitute one of the most rapidly evolving galaxy populations over the last ∼8 Gyr history of the universe. Due to their inherently compact sizes, any detailed quantitative analysis of their morphologies has proved to be difficult in the past. Hence, the morphologies and thereby the local counterparts of these enigmatic sources have been hotly debated. Aims. Our aim is to use the high angular resolution, deep, multiband HST/ACS imaging data, from the HST/ACS GOODS survey, to study the quantitative morphology of a complete sample of LCGs in the redshift range 0.5 ≤ z < 1.2. Methods. We have derived structural parameters for a representative sample of 39 LCGs selected from the GOODS-S HST/ACS field, using full 2-dimensional surface brightness profile fitting of the galaxy images in each of the four filters available. B 435w - z 850LP color maps are constructed for the sample to aid in the morphological classification. We then use the rest frame B band bulge flux fraction (BIT) to determine the morphological class of galaxies which are well fit by a bulge+disk two dimensional structure. Mergers were essentially identified visually by the presence of multiple maxima of comparable intensity in the rest frame B band images, aided by the color maps to distinguish them from HII regions. We also make use of the Spitzer 24 μm source catalog of sources in the CDFS to derive the dust enshrouded star formation rates (SFR) for some of the sample LCGs Results. We derive the following morphological mix for our sample of intermediate redshift LCGs: Mergers: ∼36%, Disk dominated: ∼22%, S0: ∼20%, Early types: ∼7%, Irr/tadpole: ∼15%. We establish that our sample LCGs are intermediate mass objects with stellar mass ranging from 9.44 < Log 10 (M/M ⊙ ) < 10.96, with a median mass of Log 10 (M/M ⊙ ) = 10.32. We also derive SFR values ranging from a few to ∼65 M ⊙ /year as expected for this class of objects. We find that LCGs account for ∼26% of the M B ≤ -20 galaxy population in the redshift range 0.5 < z ≤ 1.2. We estimate a factor∼ 11 fall in the comoving number density of blue LCGs from redshifts 0.5 < z < 1.2 to the current epoch, even though this number is subject to large uncertainties given the small sample size at zero redshift available from the literature. Conclusions. The strong redshift evolution exhibited by LCGs, and the fact that a significant fraction of LCGs are in merging systems, seem to indicate that LCGs might be an important phase in the hierarchical evolution of galaxies. We envisage that some of the LCGs that are classified as merging systems, might go on to rebuild their disks and evolve into disk galaxies in the local universe.

A comparison between SALT/SAAO observations and kilonova models for AT 2017gfo: The first electromagnetic counterpart of a gravitational wave transient - GW170817

In this Letter, we present a systematic study of lenticular (S0) galaxies based on mid-infrared imaging data on 185 objects taken using the Spitzer Infrared Array Camera. We identify the S0s hosting pseudobulges based on the position of the bulge on the Kormendy diagram and the Sersic index of the bulge. We find that pseudobulges preferentially occur in the fainter luminosity class (defined as having total K-band absolute magnitude M{sub K} fainter than -22.66 in the AB system). We present relations between bulge and disk parameters obtained as a function of the bulge type. The disks in the pseudobulge hosting galaxies are found to have distinct trends on the r{sub e}-r{sub d} and {mu}{sub d}(0)-r{sub d} correlations compared to those in galaxies with classical bulges. We show that the disks of pseudobulge hosts possess on average a smaller scale length and have a fainter central surface brightness than their counterparts occurring in classical bulge hosting galaxies. The differences found for discs in pseudobulge and classical bulge hosting galaxies may be a consequence of the different processes creating the central mass concentrations.In this Letter, we present a systematic study of lenticular (S0) galaxies based on mid-infrared imaging data on 185 objects taken using the Spitzer Infra Red Array Camera. We identify the S0s hosting pseudobulges based on the position of the bulge on the Kormendy diagram and the Sérsic index of the bulge. We find that pseudobulges preferentially occur in the fainter luminosity class (defined as having total K-band absolute magnitude MK fainter than −22.66 in the AB system). We present relations between bulge and disk parameters obtained as a function of the bulge type. The disks in the pseudobulge hosting galaxies are found to have distinct trends on the re − rd and μd(0) − rd correlations compared to those in galaxies with classical bulges. We show that the disks of pseudobulge hosts possess on average a smaller scale length and have a fainter central surface brightness than their counterparts occurring in classical bulge hosting galaxies. The differences found for discs in pseudobulge and classical bulge hosting galaxies may be a consequence of the different processes creating the central mass concentrations. Subject headings: galaxies: photometry — galaxies: formation — galaxies: fundamental parameters