We study the physical properties (size, stellar mass, luminosity, starformation rate) and scaling relations for a sample of 166 star-forming clumpswith redshift $z \sim 2-6.2$. They are magnified by the Hubble Frontier Fieldgalaxy cluster MACS~J0416 and have robust lensing magnification ($2\lesssim \mu\lesssim 82$) computed by using our high-precision lens model, based on 182multiple images. Our sample extends by $\sim 3$ times the number ofspectroscopically-confirmed lensed clumps at $z \gtrsim 2$. We identify clumpsin ultraviolet continuum images and find that, whenever the effective spatialresolution (enhanced by gravitational lensing) increases, they fragment intosmaller entities, likely reflecting the hierarchically-organized nature of starformation. Kpc-scale clumps, most commonly observed in field, are not found inour sample. The physical properties of our sample extend the parameter spacetypically probed by $z \gtrsim 1$ field observations and simulations, bypopulating the low mass (M$_\star \lesssim 10^7$ M$_\odot$), low star formationrate (SFR $\lesssim 0.5$ M$_\odot$ yr$^{-1}$), and small size (R$_\mathrm{eff}\lesssim 100$ pc) regime. The new domain probed by our study approaches theregime of compact stellar complexes and star clusters. In the mass-size plane,our sample spans the region between galaxies and globular clusters, with a fewclumps in the region populated by young star clusters and globular-clusters.For the bulk of our sample, we measure star-formation rates which are higherthan those observed locally in compact stellar systems, indicating differentconditions for star formation at high redshift than in the local Universe.
Exploring the physical properties of lensed star-forming clumps at 2 ≲ z ≲ 6
MERCURIO AMATA;
2022-01-01
Abstract
We study the physical properties (size, stellar mass, luminosity, starformation rate) and scaling relations for a sample of 166 star-forming clumpswith redshift $z \sim 2-6.2$. They are magnified by the Hubble Frontier Fieldgalaxy cluster MACS~J0416 and have robust lensing magnification ($2\lesssim \mu\lesssim 82$) computed by using our high-precision lens model, based on 182multiple images. Our sample extends by $\sim 3$ times the number ofspectroscopically-confirmed lensed clumps at $z \gtrsim 2$. We identify clumpsin ultraviolet continuum images and find that, whenever the effective spatialresolution (enhanced by gravitational lensing) increases, they fragment intosmaller entities, likely reflecting the hierarchically-organized nature of starformation. Kpc-scale clumps, most commonly observed in field, are not found inour sample. The physical properties of our sample extend the parameter spacetypically probed by $z \gtrsim 1$ field observations and simulations, bypopulating the low mass (M$_\star \lesssim 10^7$ M$_\odot$), low star formationrate (SFR $\lesssim 0.5$ M$_\odot$ yr$^{-1}$), and small size (R$_\mathrm{eff}\lesssim 100$ pc) regime. The new domain probed by our study approaches theregime of compact stellar complexes and star clusters. In the mass-size plane,our sample spans the region between galaxies and globular clusters, with a fewclumps in the region populated by young star clusters and globular-clusters.For the bulk of our sample, we measure star-formation rates which are higherthan those observed locally in compact stellar systems, indicating differentconditions for star formation at high redshift than in the local Universe.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
