Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants
Abstract
Infrared (IR) large-sky surveys allow study of how localized star formation is, enabling searches for young stellar objects (YSOs) not only at the centers of known stellar nurseries but also across the Galactic plane. However, these spatially unbiased searches suffer from contamination, most notably from dusty asymptotic giant branch (AGB) stars characterized by long-period variability. Using time-series analysis, and taking advantage of the different variability timescales of YSOs against long-period variables (LPVs), we assess the level of contamination of one of the most spatially unbiased YSO catalogs (\textit{Spitzer}/IRAC Candidate YSO, SPICY). Distinguishing between these two groups lets us draw more robust conclusions about the frequency of isolated YSOs in our Galaxy and their implications. We cross-match the SPICY and VIRAC2 catalogs (VVV/VVVX Survey), build near-IR light curves for common sources, and compute their periods and amplitudes. Contaminants are identified as sources with periodic flux variations with periods P≥ 80 d and amplitudes ΔKs≥0.35 mag. From 58 737 common sources, we identify $742$ SPICY objects as LPV contaminants based on their long-period variability, and identify $307$ high-confidence periodic YSO candidates exhibiting short-period flux changes consistent with cool spots. Near- and mid-IR amplitudes are correlated only among LPVs, suggesting a common pulsation origin. In addition, the spatial distribution of the identified populations further supports our classification, with LPVs preferentially associated with the bulge and YSOs at the lowest galactic latitudes.
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BibTeX
@misc{ordeneshuanca2026nearinfrared,
title = {{Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants}},
author = {C. Ordenes-Huanca and A. Bayo and M. Zoccali and V. Guzmán and A. Rojas-Arriagada},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37779},
eprint = {2609.37779},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37779},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Near-infrared periodicity in the SPICY catalog. True young stellar objects versus contaminants
AU - C. Ordenes-Huanca
AU - A. Bayo
AU - M. Zoccali
AU - V. Guzmán
AU - A. Rojas-Arriagada
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37779
UR - https://arxiv.org/abs/2609.37779
AB - Infrared (IR) large-sky surveys allow study of how localized star formation is, enabling searches for young stellar objects (YSOs) not only at the centers of known stellar nurseries but also across the Galactic plane. However, these spatially unbiased searches suffer from contamination, most notably from dusty asymptotic giant branch (AGB) stars characterized by long-period variability. Using time-series analysis, and taking advantage of the different variability timescales of YSOs against long-period variables (LPVs), we assess the level of contamination of one of the most spatially unbiased YSO catalogs (\textit{Spitzer}/IRAC Candidate YSO, SPICY). Distinguishing between these two groups lets us draw more robust conclusions about the frequency of isolated YSOs in our Galaxy and their implications. We cross-match the SPICY and VIRAC2 catalogs (VVV/VVVX Survey), build near-IR light curves for common sources, and compute their periods and amplitudes. Contaminants are identified as sources with periodic flux variations with periods P≥ 80 d and amplitudes ΔK_s≥0.35 mag. From 58 737 common sources, we identify $742$ SPICY objects as LPV contaminants based on their long-period variability, and identify $307$ high-confidence periodic YSO candidates exhibiting short-period flux changes consistent with cool spots. Near- and mid-IR amplitudes are correlated only among LPVs, suggesting a common pulsation origin. In addition, the spatial distribution of the identified populations further supports our classification, with LPVs preferentially associated with the bulge and YSOs at the lowest galactic latitudes.
ER -