Letter to the Editor
UVIT observations of the star-forming ring in NGC 7252: Evidence of possible AGN feedback suppressing central star formation
Indian Institute of Astrophysics,
Koramangala II Block,
2 Department of Physics, Christ University, Bangalore, India
3 National Research Council of Canada, Herzberg Astronomy and Astrophysics Research Centre, Victoria, Canada
4 National Centre for Radio Astrophysics, Pune, India
5 Tata Institute of Fundamental Research, Mumbai, India
6 University of Calgary, Calgary, Alberta, Canada
7 ISRO Satellite Centre, HAL Airport Road, Bangalore, India
8 Inter-University Center for Astronomy and Astrophysics, Pune, India
Accepted: 9 May 2018
Context. Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear.
Aims. Here we explore the pattern of recent star formation in the central region of the post-merger galaxy NGC 7252 using high-resolution ultraviolet (UV) images from the UVIT on ASTROSAT.
Methods. The UVIT images with 1.2 and 1.4 arcsec resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the central region.
Results. The FUV-NUV pixel colour map for this canonical post-merger galaxy reveals a blue circumnuclear ring of diameter ~10′′ (3.2 kpc) with bluer patches located over the ring. Based on a comparison to single stellar population models, we show that the ring is comprised of stellar populations with ages ≲300 Myr, with embedded star-forming clumps of younger age (≲150Myr).
Conclusions. The suppressed star formation in the central region, along with the recent finding of a large amount of ionised gas, leads us to speculate that this ring may be connected to past feedback from a central super-massive black hole that has ionised the hydrogen gas in the central ~4′′ ~1.3 kpc.
Key words: galaxies: elliptical and lenticular, cD / galaxies: evolution / galaxies: formation / galaxies: nuclei / galaxies: star formation / ultraviolet: galaxies
© ESO 2018