The strange case of the peculiar spiral galaxy NGC 5474. New pieces of a galactic puzzle
Abstract
We present the first analysis of the stellar content of the structures and substructures identified in the peculiar star-forming galaxy NGC 5474, based on Hubble Space Telescope resolved photometry from the LEGUS survey. NGC 5474 is a satellite of the giant spiral M 101, and it is known to have a prominent bulge that is significantly off-set from the kinematic centre of the underlying H I and stellar disc. The youngest stars (age ≲ 100 Myr) trace a flocculent spiral pattern extending out to ≳8 kpc from the centre of the galaxy. On the other hand, intermediate-age (age ≳ 500 Myr) and old (age ≳ 2 Gyr) stars dominate the off-centred bulge and a large substructure residing in the south-western part of the disc (SW over-density) and they are not correlated with the spiral arms. The old age of the stars in the SW over-density suggests that this may be another signature of any dynamical interactions that have shaped this anomalous galaxy. We suggest that a fly by with M 101, generally invoked as the origin of the anomalies, may not be sufficient to explain all the observations. A more local and more recent interaction may help to put all the pieces of this galactic puzzle together.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 2020
- DOI:
- 10.1051/0004-6361/201937284
- arXiv:
- arXiv:2001.02413
- Bibcode:
- 2020A&A...634A.124B
- Keywords:
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- galaxies: individual: NGC 5474;
- galaxies: peculiar;
- galaxies: interactions;
- galaxies: stellar content;
- galaxies: structure;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication on Astronomy &