A5003182790- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astronomy and Astrophysical Research
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Superconducting and THz Device Technology
- Dark Matter and Cosmic Phenomena
- Neutrino Physics Research
- Stellar, planetary, and galactic studies
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Complex Systems and Time Series Analysis
- Nanowire Synthesis and Applications
- Silicon Nanostructures and Photoluminescence
- Time Series Analysis and Forecasting
- Thin-Film Transistor Technologies
- Advanced Vision and Imaging
- Spectroscopy and Chemometric Analyses
- Remote Sensing in Agriculture
- Genetic diversity and population structure
- Particle Detector Development and Performance
- Calibration and Measurement Techniques
- Identification and Quantification in Food
- Advanced Text Analysis Techniques
Presidency University
2014-2023
University of KwaZulu-Natal
2012-2013
Scuola Internazionale Superiore di Studi Avanzati
2010-2011
Inter-University Centre for Astronomy and Astrophysics
2007-2010
Indian Institute of Technology Kanpur
2004
Jadavpur University
2002
<i>Aims. <i/>The <i>Herschel<i/>-ATLAS survey (H-ATLAS) will be the largest area to undertaken by <i>Herschel<i/> Space Observatory. It cover 550 sq. deg. of extragalactic sky at wavelengths 100, 160, 250, 350 and 500 <i>μ<i/>m when completed, reaching flux limits (5<i>σ<i/>) from 32 145 mJy. We here present galaxy number counts obtained for SPIRE observations first ~14 observed <i>μ<i/>m.<i>Methods. <i/>Number are a fundamental tool in constraining models evolution. use source catalogs...
We present colour–colour diagrams of detected sources in the <i>Herschel<i/>-ATLAS science demonstration field from 100 to 500 <i>μ<i/>m using both PACS and SPIRE. fit isothermal modified black bodies spectral energy distribution (SED) extract dust temperature with counterparts Galaxy And Mass Assembly (GAMA) or SDSS surveys either a spectroscopic photometric redshift. For subsample 330 at least three FIR bands significance greater than 3<i>σ<i/>, we find an average (28<i>±<i/>8) K. no known...
We use <i>Herschel<i/> PACS and SPIRE observations of the edge-on spiral galaxy UGC 4754, taken as part H-ATLAS SDP observations, to investigate dust energy balance in this galaxy. build detailed SKIRT radiative models based on SDSS UKIDSS maps these predict far-infrared emission. find that our transfer model underestimates observed FIR emission by a factor two three. Similar discrepancies have been found for other galaxies IRAS, ISO, SCUBA data. Thanks good sampling SED at wavelengths, we...
We present measurements of the angular correlation function galaxies selected from first field H-ATLAS survey. Careful removal background galactic cirrus is essential, and currently dominates uncertainty in our measurements. For 250 micron-selected sample we detect no significant clustering, consistent with expectation that sources are mostly normal at z<~ 1. 350 micron 500 samples relatively strong clustering amplitudes A 0.2 1.2 1', but large uncertainties. which preferentially select high...
We have determined the luminosity function of 250um-selected galaxies detected in ~14 sq.deg science demonstration region Herschel-ATLAS project out to a redshift z=0.5. Our findings very clearly show that evolves steadily this redshift. By selecting sub-group sources within fixed interval where incompleteness effects are minimal, we measured smooth increase comoving 250um density z=0.2 it is 3.6+1.4-0.9 times higher than local value.
We present semi-analytical models of galactic outflows in high redshift galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal pressure alone may not sustain a large scale outflow low mass (i.e $M\sim 10^8$~M$_\odot$), the presence supernovae (SNe) feedback with loading. show that inclusion ray allows solutions even these galaxies. In massive for same energy efficiency, winds can propagate to larger distances compared pure thermally winds. On an average has lower...
We present results of our time variability studies Mg II and Al III absorption lines in a sample 22 Low Ionization Broad Absorption Line QSOs (LoBAL QSOs) at 0.2 <= zem 2.1 using the 2m telescope IUCAA Girawali Observatory over time-scale 10 days to 7.69 years QSO's rest frame. Spectra are analysed conjunction with photometric light curves from Catalina Real-Time Transient Survey. Long (i.e >= 1 year) line is seen 8 cases (36% systems) while only 4 them 18% show short time-scales < year)....
We present a self-consistent, semi-analytical Λ cold dark matter (ΛCDM) model of star formation and reionization. For the cosmological parameters favoured by Wilkinson Microwave Anisotropy Probe (WMAP) data, our models consistently reproduce electron scattering optical depth to reionization, redshift reionization observed luminosity functions (LF) hence rate (SFR) density at 3 ≤z≤ 6 for reasonable range parameters. While simple photoionization feedback produces correct shape LF z= 6, we need...
We present semi-analytic models of galactic outflows, constrained by available observations on high redshift star formation and reionization. Galactic outflows are modeled in a manner akin to stellar wind blown bubbles. Large scale can generically escape from low mass halos (M<10^9 M_sun) for wide range model parameters but not (M> 10^{11} M_sun). The gas phase metallicity the outflow within galaxy computed. Ionization states different metal species calculated used examine...
We study winds in high redshift galaxies driven by a relativistic cosmic ray (proton) component addition to the hot thermal gas component. Cosmic rays (CRs) are likely be efficiently generated supernova shocks inside galaxies. obtain solutions of such CR free gravitational potential NFW form, relevant naturally provide extra energy and/or momentum input system, needed for transonic wind solution with adiabatic index $\gamma=5/3$. show that CRs can effectively drive even when is lost due...
We present a derivation of the star formation rate per comoving volume quasar host galaxies, derived from stacking analyses far-infrared to mm-wave photometry quasars with redshifts 0 < <i>z<i/> 6 and absolute <i>I<i/>-band magnitudes -22 > <i>I<i/><sub>AB<sub/> -32 use science demonstration observations first ~16 deg<sup>2<sup/> <i>Herschel<i/> Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 Sloan Digital Sky (SDSS) further 171 2dF-SDSS LRG QSO (2SLAQ) survey....
Raman spectroscopy of micron-long crystalline Si nanowires covered with a thick SiO2 layer showed downshift and asymmetric broadening the first order TO phonon peak when compared bulk (q=0) mode. The shift were attributed to confinement in nanowires. A phenomenological model, incorporating effects nanowire diameter distribution, is presented. This model shown accurately describe consistent microstructure In addition work distribution wave vector was directly taken into consideration...
The blueshift of the optical absorption edge along with intense red photoluminescence (PL) peak has been observed from micron-long crystalline silicon nanowires prepared by pulsed-laser vaporization heated Si (mixed metal catalyst) targets. Previous studies on confinement in nanostructures resulted a dispute regarding application theoretical models to explain their properties. Based microstructure phenomenological model, incorporating nanowire diameter distribution is used, which found...
To investigate the poorly constrained sub-mm counts and spectral properties of blazars we searched for these in <i>Herschel<i/>-ATLAS (H-ATLAS) science demonstration phase (SDP) survey catalog. We cross-matched 500 <i>μ<i/>m sources brighter than 50 mJy with FIRST radio catalogue. found two blazars, both previously known. Our study is among first blind blazar searches at wavelengths, i.e., regime where little still known about SEDs, but synchrotron peak most luminous expected to occur. early...
We present a semi-analytical model of star formation which explains simultaneously the observed UV luminosity function high redshift Lyman break galaxies (LBGs) and functions Lyman-alpha emitters. consider both models that use Press-Schechter (PS) Sheth-Tormen (ST) halo mass to calculate abundances dark matter halos. The at z < 4 are well reproduced with only <10% LBGs emitting lines rest equivalent width greater than limiting narrow band surveys. However, > 5 can be when we assume nearly...
We present a physically motivated semi-analytic model to understand the clustering of high-redshift Lyman-break galaxies (LBGs). show that parameters constrained by observed luminosity function can be used predict large-scale (i.e. θ ≥ 80 arcsec) bias and angular correlation galaxies. These predictions are shown reproduce observations remarkably well. then adopt these calculate halo occupation distribution (HOD) using conditional mass function. The this HOD is provide reasonably good fit...
We study prospects of constraining the primordial magnetic field (PMF) and its evolution during dark ages cosmic dawn in light EDGES 21-cm signal. Our analysis has been carried out on a `colder IGM' background which is one promising avenues to interpret consider matter-baryon interactions for excess cooling. find that colder IGM suppresses both residual free electron fraction coupling coefficient between ionised neutral components. The Compton heating also gets affected background....
Aims: We aim to demonstrate that the Herschel ATLAS (H-ATLAS) is suitable for a blind and unbiased survey debris disks by identifying candidate associated with main sequence stars in initial science demonstration field of survey. show H-ATLAS reveals population far-infrared/sub-mm sources are or star-like objects on SDSS main-sequence locus. validate our approach comparing properties most likely those known population. Methods: use photometric selection technique identify DR7 catalogue...
Laboratory experiments measuring neutrino oscillations, indicate small mass differences between different eigenstates of neutrinos. The absolute scale is however not determined, with at present the strongest upper limits coming from astronomical observations rather than terrestrial experiments. presence massive neutrinos suppresses growth perturbations below a characteristic scale, thereby leading to decreased abundance collapsed dark matter halos. Here we show that this effect can...
ABSTRACT It is extremely important to understand the processes through which thermal state of inter-galactic medium (IGM) evolved in early universe order study evolution HI 21-cm signal during cosmic dawn. Here, we consider heating IGM due ray (CR) protons generated by supernovae from both Pop III and II stars. The low energy CR (cr can escape minihalos heat via collision ionization hydrogen. Furthermore, high-energy hosting halos magnetosonic Alfvén waves. We show that these particles...