Understanding the process of Star Formation part2 (Astrophysics)
1.Constraining the physics of star formation from CIB-cosmic shear cross-correlations (arXiv)
Author : Baptiste Jego, David Alonso, Carlos García-García, Jaime Ruiz-Zapatero
Abstract : Understanding the physics of star formation is one of the key problems facing modern astrophysics. The Cosmic Infrared Background (CIB), sourced by the emission from all dusty star-forming galaxies since the epoch of reionisation, is a complementary probe to study the star formation history, as well as an important extragalactic foreground for studies of the Cosmic Microwave Background (CMB). Understanding the physics of the CIB is therefore of high importance for both cosmology and galaxy formation studies. In this paper, we make high signal-to-noise measurements of the cross-correlation between maps of the CIB from the Planck experiment, and cosmic shear measurements from the Dark Energy Survey and Kilo-Degree Survey. Cosmic shear, sourced mainly by the weak gravitational lensing of photons emitted by background galaxies, is a direct tracer of the matter distribution, and thus we can use its cross-correlation with the CIB to directly test our understanding of the link between the star formation rate (SFR) density and the matter density. We use our measurements to place constraints on a halo-based model of the SFR that parametrises the efficiency with which gas is transformed into stars as a function of halo mass and redshift. These constraints are enhanced by combining our data with model-independent measurements of the bias-weighted SFR density extracted from the tomographic cross-correlation of galaxies and the CIB. We are able to place constraints on the peak efficiency at low redshifts, η=0.445+0.055−0.11, and on the halo mass at which this peak efficiency is achieved today log10(M1/M⊙)=12.17±0.25. Our constraints are in excellent agreement with direct measurements of the SFR density, as well as other CIB-based studies
2.Smallest scale clumpy star formation in Stephan’s Quintet revealed from UV and IR imaging (arXiv)
Author : Prajwel Joseph, Koshy George, Smitha Subramanian, Chayan Mondal, Annapurni Subramaniam
Abstract : The spatial distribution and physical sizes of star forming clumps at the smallest scales provide valuable information on hierarchical star formation (SF). In this context, we report the sites of ongoing SF at ~120 pc along the interacting galaxies in Stephan’s Quintet (SQ) compact group using AstroSat-UVIT and JWST data. Since ultraviolet radiation is a direct tracer of recent SF, we identified star forming clumps in this compact group from the FUV imaging which we used to guide us to detect star forming regions on JWST IR images. The FUV imaging reveals star forming regions within which we detect smaller clumps from the higher spatial resolution images of JWST, likely produced by PAH molecules and dust ionised by FUV emission from young massive stars. This analysis reveals the importance of FUV imaging data in identifying star forming regions in the highest spatial resolution IR imaging available.
3.PHANGS: Constraining Star Formation Timescales Using the Spatial Correlations of Star Clusters and Giant Molecular Clouds (arXiv)
Author : Jordan A. Turner, Daniel A. Dale, James Lilly, Mederic Boquien, Sinan Deger, Janice C. Lee, Bradley C. Whitmore, Gagandeep S. Anand, Samantha M. Benincasa, Frank Bigiel, Guillermo A. Blanc, Melanie Chevance, Eric Emsellem, Christopher M. Faesi, Simon C. O. Glover, Kathryn Grasha, Annie Hughes, Ralf S. Klessen, Kathryn Kreckel, J. M. Diederik Kruijssen, Adam K. Leroy, Hsi-An Pan, Erik Rosolowsky, Andreas Schruba, Thomas G. Williams
Abstract : In the hierarchical view of star formation, giant molecular gas clouds (GMCs) undergo fragmentation to form small-scale structures made up of stars and star clusters. Here we study the connection between young star clusters and cold gas across a range of extragalactic environments by combining the high resolution (1") PHANGS-ALMA catalogue of GMCs with the star cluster catalogues from PHANGS-HST. The star clusters are spatially matched with the GMCs across a sample of 11 nearby star-forming galaxies with a range of galactic environments (centres, bars, spiral arms, etc.). We find that after 4–6 Myr the star clusters are no longer associated with any gas clouds. Additionally, we measure the autocorrelation of the star clusters and GMCs as well as their cross-correlation to quantify the fractal nature of hierarchical star formation. Young (≤ 10 Myr) star clusters are more strongly autocorrelated on kpc and smaller spatial scales than the >10 Myr stellar populations, indicating that the hierarchical structure dissolves over time.
