A Survey for New Members of the Taurus Star-Forming Region With the Sloan Digital Sky Survey*

Abstract

Previous studies have found that ∼1deg2 fields surrounding the stellar aggregates in the Taurus star-forming region exhibit a surplus of solar-mass stars relative to denser clusters like IC348 and the Orion Nebula Cluster. To test whether this difference reflects mass segregation in Taurus or a variation in the initial mass function, we have performed a survey for members of Taurus across a large field (∼40 deg 2 ) that was imaged by the Sloan Digital Sky Survey (SDSS). We obtained optical and near-infrared spectra of candidate members identified with those images and the Two Micron All Sky Survey, as well as miscellaneous candidates that were selected with several other diagnostics of membership. We have classified 22 of the candidates as new members of Taurus, which includes one of the coolest known members (M9.75). Our updated census of members within the SDSS field shows a surplus of solar-mass stars relative to clusters, although it is less pronounced than in the smaller fields toward the stellar aggregates that were surveyed for previously measured mass functions in Taurus. In addition to spectra of our new members, we include in our study near-IR spectra of roughly half of the known members of Taurus, which are used to refine their spectral types and extinctions. We also present an updated set of near-IR standard spectra for classifying young stars and brown dwarfs at M and L types.

The Greater Taurus–Auriga Ecosystem. I. There is a Distributed Older Population

“…Two intermediate-gravity objects that Luhman (2006) classified as young field objects are also included; one of the candidates from Gizis et al (1999) was similarly classified by Luhman (2006). While this paper was under review, Luhman et al (2017) reported additional low-mass members; they are not included in our census, but remain as evidence that the Taurus census will continue to grow with the additional of deeper and broader surveys.…”

“…Taurus has long been suggested to have an unusual IMF (Luhman 2000(Luhman , 2004Luhman et al 2009Luhman et al , 2017 Wichmann et al (1996) and Li & Hu (1998), without being confirmed at sufficient confidence to join the established census of Taurus that was promulgated by subsequent works. This trend could have been further exacerbated by the mass-dependent lifetimes of protoplanetary disks (e.g., Carpenter et al 2006).…”

“…While this paper was under review, Luhman et al (2017) published the discovery of additional late-type members of Taurus with spectral types of mid-M or later. They found that the addition of these low-mass objects lessened the deficit of brown dwarfs in comparison to the proposed excess of 0.7-1.0 M e stars.…”

Orbiting a binary

“…Together with several other targets of the same survey, HD 284149 has been proposed to be part of the so-called Taurus-Ext association (Luhman et al 2017;Kraus et al 2017;Daemgen et al 2015), a group of stars with similar space position and kinematics of the Taurus star forming region but distinctly older ages. A dedicated age estimate was then performed for HD 284149 by Bonavita et al (2014), using several youth indicators, leading to an adopted age of 25 +25 −10 Myrs.…”

A Survey For Planetary-mass Brown Dwarfs in the Taurus and Perseus Star-forming Regions*

“…The Taurus and Perseus star-forming regions are two of the most appealing targets for a brown dwarf survey because of their proximity (d = 140 and 300 pc; Torres et al 2012;Schlafly et al 2014, references therein) and the relatively large sizes of their stellar populations (N∼400 and 800, Kenyon et al 2008;Bally et al 2008). Luhman et al (2016Luhman et al ( , 2017 have provided recent summaries of previous surveys for members of Taurus and the two richest clusters in Perseus, IC 348 and NGC 1333 (see also Kraus et al (2017) for Taurus). The census of each region contains several dozen objects with spectral types indicative of brown dwarfs (>M6), most of which were identified with optical and infrared (IR) photometry.…”