Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray Sources in the Hubble Deep Field Detected by Chandra   We present first results from an X-ray study of the Hubble Deep Field North
(HDF-N) and its environs obtained using 166 ks of data collected by the
Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray
Observatory. This is the deepest X-ray observation ever reported, and in the
HDF-N itself we detect six X-ray sources down to a 0.5--8 keV flux limit of
4E-16 erg cm^-2 s^-1. Comparing these sources with objects seen in
multiwavelength HDF-N studies shows positional coincidences with the extremely
red object NICMOS J123651.74 +621221.4, an active galactic nucleus (AGN), three
elliptical galaxies, and one nearby spiral galaxy. The X-ray emission from the
ellipticals is consistent with that expected from a hot interstellar medium,
and the spiral galaxy emission may arise from a `super-Eddington' X-ray binary
or ultraluminous supernova remnant. Four of the X-ray sources have been
detected at radio wavelengths. We also place X-ray upper limits on AGN
candidates found in the HDF-N, and we present the tightest constraints yet on
X-ray emission from the SCUBA submillimeter source population. None of the 10
high-significance submillimeter sources reported in the HDF-N and its vicinity
is detected with Chandra ACIS. These sources appear to be dominated by star
formation or have AGN with Compton-thick tori and little circumnuclear X-ray
scattering.

31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
16
The categories of this paper are: stat
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas