ASTROSAT is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical and Ultra Violet spectral bands simultaneously. The payloads cover the energy bands of Ultraviolet (Near and Far), limited optical and X-ray regime (0.3 keV to 100keV). One of the unique features of ASTROSAT mission is that it enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.

ASTROSAT with a lift-off mass of 1,515 kg was launched on September 28, 2015 into a 650 km orbit inclined at an angle of 6 deg to the equator by PSLV-C30 Launch Vehicle. The minimum useful life of the ASTROSAT mission is expected to be 5 years.

The scientific objectives of ASTROSAT mission are:

o To understand high energy processes in binary star systems containing neutron stars and black holes;

o Estimate magnetic fields of neutron stars;

o Study star birth regions and high energy processes in star systems lying beyond our galaxy;

o Detect new briefly bright X-ray sources in the sky;

o Perform a limited deep field survey of the Universe in the Ultraviolet region.

At present, all the payloads are operational and are observing the cosmic sources. The spacecraft and payloads are healthy. The first six months was dedicated fo loads began.

A Jellyfish In The Sky - A Report

George Koshy and his team have used the superior resolution of UVIT to study how stars are being formed in individual parts of the tentacles of the jellyfish galaxy JO201. The paper describing their work in detail can be read here

We report the ultraviolet (UV) imaging observation of a jellyfish galaxy obtained at high spatial resolution (1.3-to-1.5 K pc) using the Ultra Violet Imaging Telescope on board ASTROSAT. Jellyfish galaxies observed in galaxy clusters are subjected to strong ram-pressure effects that strip the gas from the galaxy. The Hα images of jellyfish galaxies reveal tails of ionised gas extending up to 100 K pc, which could be hosting ongoing star formation. The star formation in the tentacles of the jellyfish galaxy JO201 in the Abell 85 galaxy cluster at red shift ∼ 0.056 is directly studied from near ultraviolet (NUV) and far ultraviolet (FUV) imaging observations.

The intense burst of star formation happening in the tentacles is the focus of the present study. JO201 is the ”UV-brightest cluster galaxy” in Abell 85 with knots and streams of star formation in the ultraviolet. We identify the star forming knots both in the stripped gas and in the galaxy disk and compare the features seen in UV with the ones traced by Hα emission from data cubes taken as part of the GASP program using MUSE on the VLT. The UV and Hα emission in main body and along the tentacles of JO201 show a remarkable correlation. We created the FUV extinction map of JO201 using the Hα and Hβ flux ratio. The star formation rates of individual knots are derived from the extinction corrected FUV emission, which agree very well with those derived from the Hα emission, and range from ∼ 0.01 -to- 2.07 M yr −1. The integrated star formation rate from FUV flux (SFRFUV ) is about ∼ 15 M /yr, which is rather typical for star forming galaxies of this mass in the local Universe. We demonstrate that the unprecedented deep UV imaging study of the jellyfish galaxy JO201 show clear sign of extra-planar star-formation activity, resulting from a recent/ongoing gas stripping event.

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