[Paper Review] New Young Stellar Object candidates in the Chamaeleon I molecular cloud discovered by DENIS

L. Cambrésy, E. Copet+6 more|arXiv (Cornell University)|Jul 8, 1998

Astrophysics and Star Formation Studies3 citations

TL;DR

This study identifies 54 new young stellar object (YSO) candidates in the Chamaeleon I molecular cloud using near-infrared J, H, and K band photometry from the DENIS survey. The candidates are selected based on their extremely red near-infrared colors, which exceed expected reddening from the cloud, and their spatial concentration in the most obscured regions, suggesting they are likely classical T Tauri stars with accretion disks, with estimated ages between 0.5 and 4 million years.

ABSTRACT

This paper presents an analysis of the nature of point sources discovered by DENIS in an area of 1.5 x 3 degrees around the Chamaeleon I molecular cloud. Most of the 30000 objects detected in the J band are background stars that were previously used to derive an accurate extinction map of the full area (Cambresy et al., 1997) using star count method. In the present work, we investigate the young stellar population of the cloud using the IJK photometric DENIS data. The whole sample of 126 already known YSOs, which are mainly T Tauri stars, are identified in the DENIS catalogue. Besides, we propose 54 sources as new candidates of YSOs. These new faint objects are selected according to their extremely red near infrared colour, that cannot be explained only by the reddening of the cloud. Moreover they are concentrated near to the most obscured areas of the cloud. Although spectroscopic confirmation is badly requested, they are interpreted as probable classical T Tauri stars that have escaped previous spectroscopic, IRAS or X-ray observations and pertaining to the low-end of the luminosity function. Assuming that they are reliable YSOs with massive accretion disks, and using theoretical pre-main-sequence tracks we estimate the age of this sample to be ranging from 5 10^5 to 4 10^6 years, an elapse of time that spans the range between the end of the star formation in the cloud and the maximum life time of the circumstellar disk.

Motivation & Objective

• To identify new young stellar object (YSO) candidates in the Chamaeleon I molecular cloud using deep near-infrared photometry.
• To investigate the low-luminosity end of the YSO population that may have been missed by prior spectroscopic, IRAS, or X-ray surveys.
• To estimate the age distribution of newly identified YSO candidates using theoretical pre-main-sequence evolutionary tracks.
• To assess the spatial correlation between the new YSO candidates and the most obscured regions of the cloud.

Proposed method

• Utilized near-infrared J, H, and K band photometry from the DENIS survey covering a 1.5° × 3° area around Chamaeleon I.
• Applied color-color and color-magnitude diagrams to distinguish YSO candidates from background stars based on their infrared colors.
• Selected sources with extremely red J-K colors that cannot be explained by interstellar reddening alone.
• Cross-referenced with known YSOs (mainly T Tauri stars) already in the literature to validate detection.
• Used theoretical pre-main-sequence evolutionary tracks to estimate the ages of the new candidates.
• Assessed spatial clustering of candidates relative to the most obscured regions of the cloud to support their association with the cloud.

Experimental results

Research questions

• RQ1 What is the nature of the faint, extremely red point sources detected in the DENIS survey toward Chamaeleon I?
• RQ2 Can these red sources be explained by interstellar reddening alone, or do they require intrinsic excess emission indicative of circumstellar disks?
• RQ3 How do the photometric properties of the new candidates compare to known T Tauri stars in the region?
• RQ4 What is the estimated age range of these new YSO candidates based on evolutionary models?
• RQ5 Is there a spatial correlation between the new YSO candidates and the densest, most obscured parts of the Chamaeleon I molecular cloud?

Key findings

• Fifty-four new YSO candidates were identified based on their extremely red J-K colors, which exceed the reddening expected from the cloud's extinction alone.
• The candidates are spatially concentrated in the most obscured regions of the Chamaeleon I molecular cloud, supporting their physical association with the cloud.
• The estimated ages of the new YSO candidates range from 0.5 to 4 million years, placing them in the phase between the end of star formation and the typical lifetime of circumstellar disks.
• The candidates are interpreted as probable classical T Tauri stars with active accretion disks, consistent with their red colors and low luminosities.
• The sample likely represents the low-luminosity end of the YSO population, previously undetected in earlier surveys such as IRAS, X-ray, or spectroscopic surveys.
• The results suggest that the DENIS survey has uncovered a significant population of low-mass, young stars in Chamaeleon I that were missed by prior observational methods.