Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of a Faint Old Stellar System at 150 kpc   We report the detection of a faint old stellar system at
$(\alpha,\delta)=(194.29^\circ,~34.32^\circ)$ (SDSS J1257+3419), based on the
spatial distribution of bright red-giant branch stars in the Sloan Digital Sky
Survey Data Release 4. SDSS J1257+3419 has a half-light radius of $38\pm 12$ pc
and an absolute integrated $V$-magnitude of $M_V=-4.8^{+1.4}_{-1.0}$ mag at a
heliocentric distance of $150\pm 15$ kpc. A comparison between SDSS J1257+3419
and known Galactic halo objects suggests that SDSS J1257+3419 is either (a) a
faint and small dwarf galaxy or (b) a faint and widely extended globular
cluster. In the former case, SDSS J1257+3419 could represent an entity of a
postulated subhalo of the Milky Way. Further photometric and dynamical study of
this stellar system is vital to discriminate these possibilities.

23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an