| Name: | Shashank Gairola |
| Affiliation: | Indian Institute of Astrophysics, Bengaluru, Karnataka, India |
| Conference ID: | ASI2025_305 |
| Title: | Tracing Hierarchical Star Formation out to Kiloparsec Scales in Nearby Galaxies |
| Authors: | Shashank Gairola 1,2, Smitha Subramanian 1, Sreedevi M. 1,3, Shyam H Menon 4,5, Chayan Mondal 6,7, Sriram Krishna 1,2, Mousumi Das 1, Annapurni Subramaniam 1 |
| Authors Affiliation: | 1 Indian Institute of Astrophysics, Koramangala II Block, Bangalore-560034, India
2 Pondicherry University, R.V. Nagar, Kalapet, 605014, Puducherry, India
3 IISER Tirupati, Srinivasapuram, Yerpedu Mandal Tirupati Dist, Andhra Pradesh, India – 517619
4 Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854, USA
5 Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA
6 Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
7 IUCAA, Post Bag 4 Ganeshkhind, Savitribai Phule Pune University campus Pune 411 007, India |
| Mode of Presentation: | Oral |
| Abstract Category: | Galaxies and Cosmology |
| Abstract: | Star formation is a hierarchical process, as revealed by the observations of its several gaseous and stellar tracers. Supersonic turbulent motions in molecular clouds produce scale-free, hierarchical density structures which undergo gravitational collapse during star formation and result in a hierarchical distribution of stellar matter in galaxies. To explore this hierarchy, we use the FUV and NUV observations of 4 nearby spiral galaxies from the Ultra-Violet Imaging Telescope (UVIT). By employing two-point correlation statistics, we find that the young star forming clumps (SFCs) in galaxies are arranged in a fractal-like, hierarchical distribution. However, this hierarchy is only observable till a maximum scale of order ~1 kpc and does not extend to the entire galaxy size. Hierarchical star formation can be sustained up to this scale by ISM turbulence originating from sources such as gravitational instabilities, cloud collisions and stellar feedback. The hierarchical distribution of SFCs randomizes over 10-50 Myr which is caused by the SFCs migrating away from their birthplaces with increasing age. We find that unlike the often-quoted, universal hierarchical properties of molecular gas, the resulting hierarchy of star formation is not universal rather, it depends on the host galaxy properties such as the nature of spiral arms, stellar mass and galactic shear. Turning our investigation towards gaseous tracers of star formation, we also analysed HII region distribution in a sample of 19 neighbouring galaxies and observed that HII regions show only mild signatures of being part of a hierarchy. Hereby, we are observing stark differences in the spatial distribution of stellar and gaseous tracers of star formation in galaxies. Through these projects which I will elucidate in my talk, we are actively investigating the role of gravity, turbulence and galaxy environment on the hierarchical star formation process in order to better understand the baryon cycle in galaxies. |
