Scale Length of Disk Galaxies in the Local Universe

TL;DR

This study analyzes the scale length and central surface brightness of nearly 30,000 local universe disk galaxies from SDSS, revealing trends across galaxy types, confirming the Freeman Law, and providing extensive data for galaxy formation models.

Contribution

It offers the largest statistical analysis of disk galaxy scale lengths and surface brightness, establishing relations across bands and revisiting the Freeman Law with a comprehensive local universe sample.

Findings

Scale lengths vary with galaxy type and mass.

The Freeman Law sets an upper limit for central surface brightness.

Late-type spirals have fainter central surface brightness.

Abstract

Disk scale length and central surface brightness for a sample of about 29955 bright disk galaxies from the Sloan Digital Sky Survey have been analysed. Cross correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scale lengths for different types of disk/spiral galaxies and present distributions and typical trends of scale lengths all the SDSS bands with linear relations that indicate the relation that connect scale lengths in one passband to another. We use the volume corrected results in the r-band and revisit the relation between these parameters and the galaxy morphology. The derived scale lengths presented here are representative for a typical galaxy mass of 10^10.8 solarmasses, and the RMS dispersion is larger for more massive galaxies. We analyse the scale-length-central disk brightness plane and further investigate the Freeman Law and confirm that it indeed defines an upper limit for disk central surface brightness in bright disks (r<17.0), and that disks in late type spirals (T > 6) have fainter central surface brightness. Our results are based on a sample of galaxies in the local universe (z< 0.3) that is two orders of magnitudes larger than any sample previously studied, and deliver statistically significant results that provide a comprehensive test bed for future theoretical studies and numerical simulations of galaxy formation and evolution.