Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tombaugh 2: The First Open Cluster with a Significant Abundance Spread
  or Embedded in a Cold Stellar Stream?   We present new abundances and radial velocities for stars in the field of the
open cluster Tombaugh 2, which has been suggested to be associated with the
Galactic Anticenter Stellar Structure (also known as the Monoceros stream).
Using VLT/FLAMES with the UVES and GIRAFFE spectrographs, we find a radial
velocity (RV) of <V_{r}> = 121 \pm 0.4 km/s using eighteen Tombaugh 2 cluster
stars. Our abundance analysis of RV-selected members finds that Tombaugh 2 is
more metal-rich than previous studies have found; moreover, unlike the previous
work, our larger sample also reveals that stars with the velocity of the
cluster show a relatively large spread in chemical properties (e.g.,
Delta[Fe/H] > 0.2). This is the first time a possible abundance spread has been
observed in an open cluster, though this is one of several possible
explanations for our observations. While there is an apparent trend of
[alpha/Fe] with [Fe/H], the distribution of abundances of these "RV cluster
members" also may hint at a possible division into two primary groups with
different mean chemical characteristics -- namely (<[Fe/H]>,<[Ti/Fe]>) ~
(-0.06, +0.02) and (-0.28, +0.36). Based on position and kinematics Tombaugh 2
is a likely member of the GASS/Monoceros stream, which makes Tombaugh 2 the
second star cluster within the originally proposed GASS/Monoceros family.
However, we explore other possible explanations for the observed spread in
abundances and two possible sub-populations, with the most likely explanation
being that the metal-poor ([Fe/H] = -0.28), more centrally-concentrated
population being the true Tombaugh 2 clusters stars and the metal-rich ([Fe/H]
= -0.06) population being an overlapping, and kinematically associated, but
"cold" (sigma_V < 2 km/s) stellar stream at R_{gc} >= 15 kpc.

24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas