Burcu Gunay | Search arXiv

arXiv2026

Sequential Star-Formation and the Near-Infrared Stellar Populations within N159

We present the first results from a JWST/NIRCam study of the star-forming region N159, one of the richest H II complexes in the Large Magellanic Cloud. This region stretches over $\sim$130 pc, and exemplifies large-scale sequential star formation. We present photometric results of $>$300,000 point sources combining data from ten near-infrared JWST filters spanning 1-4.7 microns. We detect sources as faint as $\sim$27 magnitudes at F115W, corresponding to stellar masses reaching below $\sim$0.1 $M_{\odot}$. By constructing several color-magnitude and color-color diagrams, we separate young stars from main-sequence and older stars within N159, finding evidence for stellar populations younger than 0.5 Myr. Of the young population, we identify accreting, pre-main sequence stars from their Paschen-$α$ (Pa$α$) excess and a population of sources bearing strong infrared (IR) excess, representing candidate young stellar objects (YSOs). Within this population, we identify a subpopulation of sources with H$_2$O ice absorption. The IR-excess-bearing YSO candidates correlate spatially with dust filaments and molecular gas demonstrating their embedded state. The distribution of stellar and candidate YSO populations across N159 reveal more evolved star-forming populations in the N159E region and newer star formation in the N159W region, supporting the sequential star formation scenario for this region.

astro-ph.GA↗

arXiv2025

A Tale of Two Sightlines: Comparison of Hydrocarbon Dust Absorption Bands toward Cygnus OB2-12 and the Galactic Center

Infrared spectra of hydrocarbon dust absorption bands toward the bright hypergiant Cygnus OB2-12 are compared to published spectra of the Quintuplet Cluster, a sightline to the Galactic center. The Cyg OB2-12 data include a new ground-based 2.86-3.70 microns spectrum and a previously published, but here further analyzed, spectrum of the 5.50-7.34 microns region. Higher spectral resolution data for the Cyg OB2-12 sightline in the 3 micron region allows a detailed comparison of the 3.4 micron aliphatic bands to those observed toward the Quintuplet. Despite differences in interstellar environments along each sightline, strong similarities are observed in the central wavelengths and relative strengths for bands at 3.3, 3.4, 5.85, 6.2, and 6.85 microns. Analysis of these bands, produced by aromatic, aliphatic, olefinic, hydrogenated, and oxygenated components, shows that carbonaceous dust is a significant component of the diffuse interstellar medium, second in abundance only to silicates, and is primarily aromatic in nature. The grains producing these bands likely consist of large aromatic carbon cores with thin aliphatic mantles composed of hydrogenated amorphous carbon (HAC). Laboratory analog spectra reproduce the observed aliphatic absorption bands well, supporting the presence of such mantles. We present evidence that the carriers of both the 3.4 micron aliphatic and the 3.3 micron aromatic bands reside exclusively in the diffuse ISM, and that the 3.3 micron bands observed in the diffuse ISM differ from the 3.25 micron band seen in dense clouds, implying chemically distinct carriers.

astro-ph.GA↗