| Abstract: The Balmer break (at 364.5 nm) is a prominent continuum feature commonly used to constrain the redshifts of distant galaxies, estimate the ages of their stellar populations, and infer their star-formation histories. It becomes evident in integrated spectra when the light is dominated by A-type stars. In the case of an instantaneous burst of star formation, the Balmer break emerges after around a hundred million years. Measuring the strength of this feature for large galaxy samples provides constraints on their ages and star-formation histories, thereby offering insights into galaxy evolution over cosmic time (e.g., Belli et al. 2019).
In this talk, we discuss the potential of measuring the Balmer break strength from photometry at redshifts 3 to 10 using JWST/NIRCam observations obtained as part of several large photometric surveys (CEERS, JADES, FRESCO, and PRIMER). We demonstrate that adequate photometric bands, within specific redshift intervals, can measure the strength of the Balmer break with an accuracy comparable to spectroscopic observations.
We demonstrate that the Balmer break strength shows an evolution with redshift from the cosmic dawn to cosmic noon, which might be primarily driven by the age of the stellar population. We also show the median Balmer break strength in various redshift intervals and the correlation of the Balmer break strength with various physical parameters such as mass, age, specific star formation rate, etc. We also examine the effect of physical parameters on break strength from a modelling perspective and compare our observational results with theoretical expectations. Finally, we discuss some individual Balmer break objects in the epoch of reionization (e.g., Kuruvanthodi et al. 2024), which include post-starburst galaxies, mini-quenched galaxies, and Little Red Dots (LRDs).
Overall, our analysis provides clues about galaxy quenching, the nature of star formation, and the onset of star formation in the early universe. |
