Abhirup Datta

Indian Institute of Technology Indore, Astronomy, Astrophysics and Space Engineering, Faculty Member

University of Colorado, Boulder, Center for Astrophysics and Space Astronomy, Research Associate

Followers

118

Following

Co-authors

Public Views

Phone: 8518886478
Address: Department of Astronomy, Astrophysics and Space Engineering,
Indian Institute of Technology Indore
Simrol, Khandwa Road, Indore-452020, M.P., India

less

InterestsView All (29)

Uploads

Papers by Abhirup Datta

The VLA-COSMOS survey. IV. (Schinnerer+, 2010)

by Anton M Koekemoer and Abhirup Datta

The central seven pointings of the mosaic for the VLA-COSMOS Large project (pointing numbers: F07... more The central seven pointings of the mosaic for the VLA-COSMOS Large project (pointing numbers: F07, F08, F11, F12, F13, F16, F17) were observed using the VLA A configuration in 2006 February and March. The observations were executed on 11 days. ------------------------------------ Pointing RA (J2000) DE (J2000) ------------------------------------ F07 10 00 58.62 +02 25 20.42 F08 09 59 58.58 +02 25 20.42 F11 10 01 28.64 +02 12 21.00 F12 10 00 28.60 +02 12 21.00 F13 09 59 28.56 +02 12 21.00 F16 10 00 58.62 +01 59 21.58 F17 09 59 58.58 +01 59 21.58 ------------------------------------ (1 data file).

Exploring the Dark Ages and Epoch of Reionization with the HI 21 cm signal

Dark Ages Radio Explorer - Field Tests of a Prototype Instrument

Dark Ages Radio Explorer Instrument Verification Program: Antenna Test Results

American …, Jan 1, 2012

ABSTRACT Observations of the HI 21 cm transition line promises to be an important probe into the ... more ABSTRACT Observations of the HI 21 cm transition line promises to be an important probe into the cosmic Dark Ages and Epoch of Reionization. The Dark Ages Radio Explorer (DARE) is designed to measure the sky-averaged 21-cm signal from this cosmic age using a single radiometer operating between 40-120 MHz (redshifts z=11-35). DARE will orbit the Moon for a mission lifetime of ≤ 3 years and take data above the lunar far side, where it is shielded from the Earth&#39;s intense interference. The science objectives of DARE include formation of first stars, first accreting black holes, beginning of reionization and end of the Dark Ages. The science instrument is composed of a three-element radiometer, including electrically-short, tapered, bi-conical dipole antennas, a receiver, and a digital spectrometer. Although the TRL (Technology Readiness Level) of the individual components of DARE instrument is high, the overall instrument TRL is low. One of the main aim of the entire DARE team is to advance the instrument TRL. In this work we mainly focus on the development work for DARE Antenna. We will present the initial test results of a prototype DARE antenna, fabricated in NRAO. Some CST simulations using the actual DARE experiment set up have also been performed. In future, we plan to perform extensive tests to characterize the beam pattern and spectral response of the prototype DARE instrument design. In order to utilize the anechoic chamber available at NRAO, we will use a half-scale version of the DARE antenna (120-200 MHz). The full-scale version of the DARE antenna (40-120 MHz) along with the final version of the DARE receiver will be used for outdoor tests in the low-RFI environment of Western Australia. We will also present the initial software development for analyzing the test results from the prototype DARE antenna and receiver.

A Medium-Scale Traveling Ionospheric Disturbance Observed from the Ground and from Space

AGU Fall Meeting …, Jan 1, 2008

format_quoteVLA observed wave structures with phase progressions that align with techniques for isolating ionospheric contributions from signal noise.format_quote

Download

Star Formation Rates in Lyman Break Galaxies: Radio Stacking of LBGs in the COSMOS Field and the Sub-μJy Radio Source Population

The Astrophysical …, Jan 1, 2008

We present an analysis of the radio properties of large samples of Lyman Break Galaxies (LBGs) at... more We present an analysis of the radio properties of large samples of Lyman Break Galaxies (LBGs) at z ∼ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ∼ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 ± 0.21µJy. The stacked emission is unresolved, with a size < 1", or a physical size < 8kpc. The total star formation rate implied by this radio luminosity is 31 ± 7 M ⊙ year −1 , based on the radio-FIR correlation in low redshift star forming galaxies. The star formation rate derived from a similar analysis of the UV luminosities is 17 M ⊙ year −1 , without any correction for UV dust attenuation. The simplest conclusion is that the dust attenuation factor is 1.8 at UV wavelengths. However, this factor is considerably ⋆ Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4m, CTIO 4m, and CFHT 3.6m.

format_quoteStatistical detection of z ∼ 3 LBGs shows 1.4 GHz flux density of 0.90 ± 0.21µJy, implying star formation rate of 31 ± 7 M ⊙ year -1.format_quote

Download

Detection of Signals from Cosmic Reionization using Radio Interferometric Signal Processing

The Astrophysical Journal, Jan 1, 2009

Observations of the HI 21cm transition line promises to be an important probe into the cosmic dar... more Observations of the HI 21cm transition line promises to be an important probe into the cosmic dark ages and epoch of reionization. One of the challenges for the detection of this signal is the accuracy of the foreground source removal. This paper investigates the extragalactic point source contamination and how accurately the bright sources ( 1 Jy) should be removed in order to reach the desired RMS noise and be able to detect the 21cm transition line. Here, we consider position and flux errors in the global sky-model for these bright sources as well as the frequency independent residual calibration errors. The synthesized beam is the only frequency dependent term included here. This work determines the level of accuracy for the calibration and source removal schemes and puts forward constraints for the design of the cosmic reionization data reduction scheme for the upcoming low frequency arrays like MWA,PAPER, etc. We show that in order to detect the reionization signal the bright sources need to be removed from the data-sets with a positional accuracy of ∼ 0.1 arc-second. Our results also demonstrate that the efficient foreground source removal strategies can only tolerate a frequency independent antenna based mean residual calibration error of 0.2% in amplitude or 0.2 degree in phase, if they are constant over each days of observations (6 hours). In future papers we will extend this analysis to the power spectral domain and also include the frequency dependent calibration errors and direction dependent errors (ionosphere, primary beam, etc).

Download

The VLA-COSMOS Survey. IV. Deep Data and Joint Catalog

The Astrophysical …, Jan 1, 2010

In the context of the VLA-COSMOS Deep project additional VLA A array observations at 1.4 GHz were... more In the context of the VLA-COSMOS Deep project additional VLA A array observations at 1.4 GHz were obtained for the central degree of the COSMOS field and combined with the existing data from the VLA-COSMOS Large project. A newly constructed Deep mosaic with a resolution of 2.5 ′′ was used to search for sources down to 4σ with 1σ ≈ 12 µJy/beam in the central 50 ′ ×50 ′ . This new catalog is combined with the catalog from the Large project (obtained at 1.5 ′′ ×1.4 ′′ resolution) to construct a new Joint catalog. All sources listed in the new Joint catalog have peak flux densities of ≥5σ at 1.5 ′′ and/or 2.5 ′′ resolution to account for the fact that a significant fraction of sources at these low flux levels are expected to be slighty resolved at 1.5 ′′ resolution. All properties listed in the Joint catalog such as peak flux density, integrated flux density and source size are determined in the 2.5 ′′ resolution Deep image. In addition, the Joint catalog contains 43 newly identified multi-component sources.

Download

Bright Source Subtraction Requirements for Redshifted 21 cm Measurements

The Astrophysical Journal, Jan 1, 2010

The HI 21 cm transition line is expected to be an important probe into the cosmic dark ages and e... more The HI 21 cm transition line is expected to be an important probe into the cosmic dark ages and epoch of reionization. Foreground source removal is one of the principal challenges for the detection of this signal. This paper investigates the extragalactic point source contamination and how accurately bright sources ( 1 Jy) must be removed in order to detect 21 cm emission with upcoming radio telescopes such as the Murchison Widefield Array (MWA). We consider the residual contamination in 21 cm maps and power spectra due to position errors in the sky-model for bright sources, as well as frequency independent calibration errors. We find that a source position accuracy of 0.1 arcsec will suffice for detection of the HI power spectrum. For calibration errors, 0.05 % accuracy in antenna gain amplitude is required in order to detect the cosmic signal. Both sources of subtraction error produce residuals that are localized to small angular scales, k ⊥ 0.05 Mpc −1 , in the two-dimensional power spectrum.

Download

Imaging of the CCS 22.3 GHz emission in the Taurus Molecular Cloud complex

by Abhirup Datta and Nirupam Roy

Arxiv preprint arXiv:1106.4011, Jan 1, 2011

Thioxoethenylidene (CCS) is an abundant interstellar molecule, and a good tracer of high density ... more Thioxoethenylidene (CCS) is an abundant interstellar molecule, and a good tracer of high density and evolutionary stage of dense molecular clouds. It is also a suitable candidate for Zeeman splitting observations for its high splitting factor and narrow thermal linewidths. We report here EVLA 22.3 GHz observations of three dense molecular cores TMC-1, TMC-1C and L1521B in the Taurus Molecular Cloud complex to image the CCS 2 1 − 1 0 transition. For all three sources, the clumpy CCS emission is most likely tracing the starless cores. However, these compact structures account for only ∼ 1 − 13% of the integrated emission detected in single-dish observations, indicating the presence of significant large scale diffuse emission in favorable conditions for producing CCS.

format_quoteEvLA detected only 1-13% of CCS emission in compact structures; majority from large-scale configurations beyond resolution limit.format_quote

Download

Searching For Cosmic Reionization With The Hi 21cm Signal

Bulletin of the American …, Jan 1, 2010

One of the most difficult challenges for the detection of the HI 21cm signal during cosmological ... more

Citation: Dymond, KF, et al.(2011), A Medium-Scale Traveling Ionospheric Disturbance Observed from the Ground and from Space, Radio Sci., doi: 10.1029/ …

agu.org

First limits to the neutral IGM during cosmic reionization using the Hydrogen 2p-2s transition in absorption

ATNF proposal# …, Jan 1, 2008

Cosmic reionization, the transition in the early universe from a neutral to an ionized intergalac... more Cosmic reionization, the transition in the early universe from a neutral to an ionized intergalactic medium, is the last major epoch of cosmic evolution left to explore. Study of the IGM, galaxies, and quasars present during this time is a primary science driver for nearly all future large-area telescopes. Mapping reionization through the redshifted 21 cm line is planned (e.g.,

PAPER's Sweet Sixteen: Imaging the Low-Frequency Sky with a Sixteen-Element Array

2009 USNC/URSI …, Jan 1, 2009