**QHSC Quasar Candidate Catalog**

We present the QHSC catalog — a machine-learning–selected sample of quasar candidates 
with photometric redshifts identified in the Wide layer of the HSC-SSP survey 
(Public Data Release 3). 

The complete QHSC catalog includes four distinct subsamples:
1. A master sample based on HSC-only photometry.
2. An HSC+WISE sample combining optical and mid-infrared data.
3. The GoldenU sample, incorporating near-infrared photometry from UKIDSS.
4. The GoldenV sample, incorporating near-infrared photometry from VISTA.

These four subsamples are stored as separate FITS extensions within the catalog file 
named "QHSC.fits".

1. Python Example: Loading the QHSC Catalog

"""Python
from astropy.table import Table
from astropy.io import fits

hdul = fits.open('<.../QHSC.fits>')

tbl_master   = Table.read(hdul['Master'])
tbl_hsc_wise = Table.read(hdul['HSC+WISE'])
tbl_goldenU  = Table.read(hdul['GoldenU'])
tbl_goldenV  = Table.read(hdul['GoldenV'])
"""

2. Columns Description

(Note: All magnitudes are given in the AB system.)
--------------------------------------------

1.  object_id: Unique HSC object ID (64-bit integer)
2.  ra: Right Ascension (J2000) from HSC
3.  dec: Declination (J2000) from HSC
4.  pQSO: Probability of the object being a quasar
5.  z_ML: Photometric redshift estimated by the bsXGBoost model
6.  z_ML_std: Model uncertainty of the estimated photometric redshift
7.  ebv: Galactic extinction E(B−V) from the SFD dust map, scaled by a factor of 0.86
... x_image_flag: HSC image quality flag for band x, where x ∈ {g, r, i, z, y}
... flag_x_aper: Aperture photometry flag in HSC band x
... mag_x_aper: Aperture magnitude in HSC band x
... magerr_x_aper: Error of aperture magnitude in HSC band x
... flag_x_psf: PSF photometry flag in HSC band x
... mag_x_psf: PSF magnitude in HSC band x
... magerr_x_psf: Error of PSF magnitude in HSC band x
... flag_x_cmodel: CModel photometry flag in HSC band x
... mag_x_cmodel: CModel magnitude in HSC band x
... magerr_x_cmodel: Error of CModel magnitude in HSC band x

--------------------------------------------
QHSC HSC+WISE
--------------------------------------------

58. name_catwise: CatWISE2020 source name
59. mag_W1: W1 magnitude from profile-fit photometry with motion correction
60. magerr_W1: Error of W1 magnitude
61. mag_W2: W2 magnitude from profile-fit photometry with motion correction
62. magerr_W2: Error of W2 magnitude

--------------------------------------------
QHSC Golden (UKIDSS)
--------------------------------------------

63. id_ukidss: Unique UKIDSS source ID
64. ukidss_survey: UKIDSS sub-survey name (e.g., LAS, DXS, or UDS)
65. mag_J: UKIDSS J-band aperture corrected magnitude (2''aperture diameter)
66. magerr_J: Error of J-band magnitude from UKIDSS
67. mag_H: UKIDSS H-band aperture corrected magnitude (2'' aperture diameter)
68. magerr_H: Error of H-band magnitude from UKIDSS
69. mag_K: UKIDSS K-band aperture corrected magnitude (2''aperture diameter)
70. magerr_K: Error of K-band magnitude from UKIDSS

--------------------------------------------
QHSC Golden (VISTA)
--------------------------------------------

63. id_vista: Unique VISTA source ID
64. vista_survey: VISTA survey name (e.g., VIKING, VHS, VIDEO, or UltraVISTA)
65. mag_J: VISTA J-band aperture corrected magnitude (2″ aperture diameter)
66. magerr_J: Error of J-band magnitude from VISTA
67. mag_H: VISTA H-band aperture corrected magnitude (2″ aperture diameter)
68. magerr_H: Error of H-band magnitude from VISTA
69. mag_Ks: VISTA Ks-band aperture corrected magnitude (2″ aperture diameter)
70. magerr_Ks: Error of Ks-band magnitude from VISTA

Note: If you use the QHSC catalog, please cite Zhu et al. 2025 (Accepted for publication in ApJS).