Young Stellar Objects in Lynds 1641: Disks, Accretion, and Star Formation History

TL;DR

This study analyzes young stellar objects in Lynds 1641 using multi-wavelength data to understand their disks, accretion, and star formation history, revealing insights into disk evolution, accretion variability, and star formation modes.

Contribution

It provides a comprehensive characterization of YSOs in L1641, including new transition disk identifications, accretion rates, and evidence for different star formation modes and history.

Findings

Disk fraction ~50% in L1641.

Accretion variability cannot explain scatter in accretion rates.

Star formation in L1641 started 2-3 Myr ago.

Abstract

We investigate the young stellar objects (YSOs) in the Lynds~1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, 2MASS, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy. We use this data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, as well as accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log(M_*/M_sun)\approx-0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40--45% vs. 77--79% respectively). We confirm our previous result that the accreting TDs have a similar median accretion rate to normal optically thick disks. We confirm that two star formation modes (isolated vs. clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically-thick disks and the transition disk objects have a median age which is intermediate between the two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2--3 Myr ago.