Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Typical Massive Quiescent Galaxy at z$\sim$3 is a Post-starburst   We have obtained spectroscopic confirmation with Hubble Space Telescope
WFC3/G141 of a first sizeable sample of nine quiescent galaxies at 2.4<z<3.3.
Their average near-UV/optical rest-frame spectrum is characterized by low
attenuation (Av$\sim$0.6 mag) and a strong Balmer break, larger than the 4000 A
break, corresponding to a fairly young age of $\sim$300 Myr. This formally
classifies a substantial fraction of classically selected quiescent galaxies at
z $\sim$ 3 as post-starbursts, marking their convergence to the quenching
epoch. The rapid spectral evolution with respect to z $\sim$ 1.5 quiescent
galaxies is not matched by an increase of residual star-formation, as judged
from the weak detection of [O II]3727A emission, pointing to a flattening of
the steep increase in gas fractions previously seen from z $\sim$ 0 to 1.8.
However, radio 3GHz stacked emission implies either much stronger dust-obscured
star formation or substantial further evolution in radio-mode AGN activity with
respect to z $\sim$ 1.5.

18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas