LACEwING: A New Moving Group Analysis Code

Abstract

We present a new nearby young moving group (NYMG) kinematic membership analysis code, LocAting Constituent mEmbers In Nearby Groups (LACEwING), a new Catalog of Suspected Nearby Young Stars, a new list of bona fide members of moving groups, and a kinematic traceback code. LACEwING is a convergence-style algorithm with carefully vetted membership statistics based on a large numerical simulation of the Solar Neighborhood. Given spatial and kinematic information on stars, LACEwING calculates membership probabilities in 13 NYMGs and three open clusters within 100 pc. In addition to describing the inputs, methods, and products of the code, we provide comparisons of LACEwING to other popular kinematic moving group membership identification codes. As a proof of concept, we use LACEwING to reconsider the membership of 930 stellar systems in the Solar Neighborhood (within 100 pc) that have reported measurable lithium equivalent widths. We quantify the evidence in support of a population of young stars not attached to any NYMGs, which is a possible sign of new as-yet-undiscovered groups or of a field population of young stars.

Young Stars with SALT*

“…As noted in Riedel (2012), these selection criteria biased the sample toward detecting young stars for two major reasons. First, the space velocities of the nearby young moving groups are clustered around the local standard of rest and thus their members fall within the proper motion selection criteria.…”

“…The RECONS 1 TINY proper MOtions (TINYMO) survey (Riedel 2012) delivered a number of new moving group members, many already published in Riedel et al (2014). Given that the survey has already yielded 26 young stars out of the 55 that have been followed up with astrometry, it is reasonable to assume that the survey may contain many other young stars.…”

“…This exploits a property of the J − K color, in that when it is plotted against V − K (or any other optical band -K), the locus of giant stars separates from main sequence dwarfs over the approximate spectral type range M1-M6 (Riedel 2012). Consequently, most of the stars in the survey and this paper are of those spectral types, and most of the targets (though not all) have SuperCOSMOS proper motions less than 0.18 ′′ yr −1 .…”

“…In Riedel (2012) and the subsequent work outlined in Riedel et al (2014), trigonometric parallaxes and spectroscopy were obtained for a subset of identified low-propermotion M dwarfs whose photometric distances were estimated to place them within 15 parsecs of the Sun, with preference to stars exhibiting X-ray emission (from the ROSAT All-Sky Survey) as a sign of coronal activity.…”

“…SAMPLE The sample of stars were drawn from the TINYMO survey (Riedel 2012). In that survey, nearby low-proper-motion M dwarfs in the southern hemisphere were identified in the SuperCOSMOS Science Archive (Hambly et al 2001b).…”