Smitha Subramanian

Depth Estimation of the Large and Small Magellanic Clouds

Context. A systematic estimation of the line of sight depth in the disk and bar regions of the Large and Small Magellanic Clouds (LMC and SMC) using red clump stars is presented. Aims. We used the red clump stars from the photometric data of the Optical Gravitational Lensing Experiment (OGLE II) survey and the Magellanic Cloud Photometric Survey (MCPS) for both the Clouds to estimate the depth. Methods. The observed dispersion in the magnitude and colour distribution of red clump stars is used to estimate the depth, after correcting for population effects, internal reddening within the Clouds and photometric errors. Results. The observed dispersion due to the line of sight depth ranges from 0.023 mag, to 0.45 mag (a depth of 500 pc to 10.4 kpc) for the LMC and, from 0.025 to 0.34 mag (a depth of 670 pc to 9.53 kpc) for the SMC. The minimum value corresponds to the dispersion that can be estimated due to errors. The depth profile of the LMC bar indicates that it is flared. The average depth in the bar region is 4.0 ± 1.4 kpc. The northern disk is found to have depth (4.17 ± 0.97 kpc) larger than the southern part of the disk (2.63 ± 0.8 kpc). There is no indication of depth variation between the eastern (2.8 ± 0.92 kpc) and the western (3.09 ± 0.99 kpc) disk. The average depth for the disk is 3.44 ± 1.16 kpc. The SMC is found to have larger depth than the LMC. In the case of the SMC, the bar depth (4.90 ± 1.23 kpc) and the disk depth (4.23 ± 1.48 kpc) are found to be within the standard deviations. A prominent feature in the SMC is the increase in depth near the optical center. The averaged depth profile near the center resembles a structure like a bulge. Conclusions. The large dispersions estimated in the LMC bar and the northern disk suggest that the LMC either has large depth and/or different stellar population in these regions. The halo of the LMC (using RR Lyrae stars) is found to have larger depth compared to the disk/bar, which supports the existence of an inner halo for the LMC. On the other hand, the estimated depths for the halo (RR Lyrae stars) and disk are found to be similar, for the SMC bar region. Thus, increased depth and enhanced stellar as well as HI density near the optical center suggests that the SMC may have a bulge.

The VMC survey - XIV : First results on the look-back time star formation rate tomography of the Small Magellanic Cloud

We analyse deep images from the VISTA survey of the Magellanic Clouds in the YJKs filters, covering 14 sqrdeg (10 tiles), split into 120 subregions, and comprising the main body and Wing of the Small Magellanic Cloud (SMC). We apply a colour--magnitude diagram reconstruction method that returns their best-fitting star formation rate SFR(t), age-metallicity relation (AMR), distance and mean reddening, together with 68% confidence intervals. The distance data can be approximated by a plane tilted in the East-West direction with a mean inclination of 39 deg, although deviations of up to 3 kpc suggest a distorted and warped disk. After assigning to every observed star a probability of belonging to a given age-metallicity interval, we build high-resolution population maps. These dramatically reveal the flocculent nature of the young star-forming regions and the nearly smooth features traced by older stellar generations. They document the formation of the SMC Wing at ages <0.2 Gyr and the peak of star formation in the SMC Bar at 40 Myr. We clearly detect periods of enhanced star formation at 1.5 Gyr and 5 Gyr. The former is possibly related to a new feature found in the AMR, which suggests ingestion of metal-poor gas at ages slightly larger than 1 Gyr. The latter constitutes a major period of stellar mass formation. We confirm that the SFR(t) was moderately low at even older ages.

The VMC Survey – XIII. Type II Cepheids in the Large Magellanic Cloud

The VISTA survey of the Magellanic Clouds System (VMC) is collecting deep

Structure of the Large Magellanic Cloud from near infrared magnitudes of red clump stars

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Disk of the Small Magellanic Cloud as traced by Cepheids

--band time--series photometry of the pulsating variable stars hosted in the system formed by the two Magellanic Clouds and the Bridge connecting them. In this paper we have analysed a sample of 130 Large Magellanic Cloud (LMC) Type II Cepheids (T2CEPs) found in tiles with complete or near complete VMC observations for which identification and optical magnitudes were obtained from the OGLE III survey. We present

The VMC Survey – XXIV. Signatures of tidally stripped stellar populations from the inner Small Magellanic Cloud

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The VMC survey - XXVI. Structure of the Small Magellanic Cloud from RR Lyrae stars

and

The VMC Survey. XXII. Hierarchical Star Formation in the 30 Doradus-N158–N159–N160 Star-forming Complex

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Investigating AGN black hole masses and the MBH–σe relation for low surface brightness galaxies

light curves for all 130 pulsators, including 41 BL Her, 62 W Vir (12 pW Vir) and 27 RV Tau variables. We complement our near-infrared photometry with the

The VMC Survey. XXIX. Turbulence-controlled Hierarchical Star Formation in the Small Magellanic Cloud

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