Near-Infrared photometry of carbon stars in the Sagittarius dwarf irregular galaxy and DDO 210

TL;DR

This study uses near-infrared photometry to identify and analyze the carbon star populations in the dwarf irregular galaxies DDO 210 and SagDIG, revealing new candidates and providing insights into their star formation histories.

Contribution

It demonstrates the effectiveness of near-IR photometry for detecting carbon stars and expands the known populations in these galaxies, offering new data for understanding their star formation.

Findings

Discovered six new carbon stars in DDO 210.

Identified six new carbon stars in SagDIG.

Provided constraints on star formation history from luminosity functions.

Abstract

We investigate the intermediate-age asymptotic giant branch stellar population of two Local Group dwarf irregular galaxies to characterize their carbon star population in near-infrared (IR). Our work is based on J and K-band SOFI near-IR photometry complemented with optical ground based and HST photometry. We show that near-IR photometry is a very powerful tool for carbon star detection. We recovered two out of three previously-known carbon stars in DDO 210 and discovered six additional objects in this galaxy which have optical and near-IR colors consistent with carbon giants. This brings the total number of bona-fide C-star candidates in DDO 210 to nine. We detected a large population of C-star candidates in SagDIG, 18 of which were previously identified in Demers & Battinelli (2002) and Cook (1987), and six new bona-fide carbon stars. We present their optical and near-IR colors and use their luminosity function to put constraints on the star formation history (SFH) in this dwarf irregular galaxy.