2WHSP Catalog of High Synchrotron Peaked Blazars and Candidates
Short Name:
WISEHSPCAT
Date:
18 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
High Synchrotron Peaked blazars (HSPs) dominate the gamma-ray sky at energies larger than a few GeV, however only a few hundred blazars of this type have been catalogued so far. In this paper, the authors present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalog (Arsioli et al. 2015, A&A, 579, A34) of gamma-ray source candidates away from the Galactic Plane. They cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR, and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs, the authors examined the spectral energy distribution (SED) of each candidate and estimated the peak frequency of its synchrotron emission (nu<sub>peak</sub>) using the Agenzia Spaziale Italiana Science Data Center (ASDC) SED tool, including only sources with nu<sub>peak</sub> > 10<sup>15</sup> Hz (equivalent to nu<sub>peak</sub> > 4 eV). The authors have assembled the largest and most complete catalog of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colors, synchrotron peak, redshift distributions, and gamma-ray spectral properties, have been used to characterize the sample and maximize completeness. The authors also derived the radio log N - log S distribution. This catalog has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra-high energy cosmic ray sources, showing its potential for the identification of promising high-energy gamma-ray sources and multi-messenger targets. This table comprises the 2WHSP catalog, a multi-frequency catalog of HSP. It contains 1691 sources, 288 of which are newly identified HSPs, 540 are previously known HSPs, 814 are HSP candidates, 45 are HSP blazars taken from the 2FHL catalog, and 4 from TeVCat (<a href="http://tevcat.uchicago.edu">http://tevcat.uchicago.edu</a>). This table was created by the HEASARC in February 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A17">CDS Catalog J/A+A/598/A17</a> file 2whsp.dat. This is a service provided by NASA HEASARC .
