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WISEHSPCAT - 2WHSP Catalog of High Synchrotron Peaked Blazars and Candidates

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Overview

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 (nupeak) using the Agenzia Spaziale Italiana Science Data Center (ASDC) SED tool, including only sources with nupeak > 1015 Hz (equivalent to nupeak > 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 (http://tevcat.uchicago.edu).


Catalog Bibcode

2017A&A...598A..17C

References

2WHSP: A multi-frequency selected catalogue of high energy and very high energy
gamma-ray blazars and blazar candidates.
    Chang Y.-L., Arsioli B., Giommi P., Padovani, P.
    <Astron. Astrophys. 598, A17 (2017)>
    =2017A&A...598A..17C        (SIMBAD/NED BibCode)

1WHSP: an IR-based sample of ~ 1,000 VHE gamma-ray blazar candidates.
    Arsioli B., Fraga B., Giommi P., Padovani P., Marrese P.M.
   <Astron. Astrophys. 579, A34 (2015)>
   =2015A&A...579A..34A        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in February 2017 based on CDS Catalog J/A+A/598/A17 file 2whsp.dat.

Parameters

Name
The J2000.0 position-based designation of the object, viz., 2WHSP JHHMMSS.s+DDMMSS, where the prefix stands for 2nd WISE High Synchrotron Peaked blazar, in the general style recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the HSP blazar/blazar candidate based on its position in the All-WISE Catalog (Cutri et al. 2013) in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 0.1 seconds of time in the name specified in the original table. One good HSP blazar found among the 2FHL low Galactic latitude sources had no WISE data (2WHSP J135340.2-663958). The authors used the radio position instead of the IR position in this case.

Dec
The Declination of the HSP blazar/blazar candidate based on its position in the All-WISE Catalog (Cutri et al. 2013) in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 1 arcsecond in the name specified in the original table. One good HSP blazar found among the 2FHL low Galactic latitude sources had no WISE data (2WHSP J135340.2-663958). The authors used the radio position instead of the IR position in this case.

LII
The Galactic Longitude of the HSP blazar/blazar candidate.

BII
The Galactic Latitude of the HSP blazar/blazar candidate.

Source_Flag
This parameter contains a flag which is set to 'U' (changed from '*' in the original table) to indicates that the source is an uncertain member of this class of object, typically owing to the lack of good multi-frequency data.

Bzcat_Object_Type
The 5BZCat (5th Roma-BZCAT, Massaro et al. 2015, Ap&SS, 357, 75, available at the HEASARC as the ROMABZCAT table) name prefix, the last letter of which codes the blazar sub-type, as follows:

   5BZB = BL Lac objects, used for AGNs with a featureless optical
          spectrum, or having only absorption lines of galaxian origin and weak
          and narrow emission lines;
   5BZG = sources, usually reported as BL Lac objects in the literature,
          but having a spectral energy distribution (SED) with a significant
          dominance of the galaxian emission over the nuclear one
   5BZQ = Flat Spectrum Radio Quasars, with an optical spectrum showing
          broad emission lines and dominant blazar characteristics;
   5BZU = blazars of uncertain type, adopted for a small number of sources
          having peculiar characteristics but also exhibiting blazar activity:
          for instance, occasional presence/absence of broad spectral lines or
          other features, transition objects between a radio galaxy and a BL
          Lac, galaxies hosting a low luminosity blazar nucleus, etc.
  

Log_Nu_Peak_Limit
This limit flag is set to '>' if the quoted value of the corresponding parameter is a lower limit rather than an actual value. The lower limits and uncertain values of log_nu_peak and log_nu_f_nu are due to limited data, specially in the X-ray band.

Log_Nu_Peak
The logarithm of the observed peak frequency of the synchrotron bump, in Hz.

Log_Nu_Peak_Flag
This parameter contains a flag which is set to ':' (changed from '*' in the original table) to indicates that the value of the corresponding parameter is considered to be uncertain. The lower limits and uncertain values of log_nu_peak and log_nu_f_nu are due to limited data, specially in the X-ray band.

Log_Nu_F_Nu_Limit
This limit flag is set to '>' if the quoted value of the corresponding parameter is a lower limit rather than an actual value.

Log_Nu_F_Nu
The logarithm of the product of the observed peak flux density and the peak frequency, nupeak * f(nupeak), of the synchrotron bump, in erg cm-2 s-1.

Log_Nu_F_Nu_Flag
This parameter contains a flag which is set to ':' (changed from '*' in the original table) to indicates that the value of the corresponding parameter is considered to be uncertain. The lower limits and uncertain values of log_nu_peak and log_nu_f_nu are due to limited data, specially in the X-ray band.

Redshift_Limit
This limit flag is set to '>' if the quoted value of the corresponding parameter is a lower limit rather than an actual value.

Redshift
The redshift of the HSP blazar/blazar candidate, if available.

Redshift_Flag
This parameter contains a flag which is set to ':' (changed from '*' in the original table) to indicates that the value of the corresponding parameter is considered to be uncertain.

Ref_Redshift
This parameter contains a reference code [bcdefg] for the quoted redshift, as follows:

     b = Pita et al. (2014, A&A, 565, A12)
     c = Furniss et al. (2013, ApJ, 768L, 31)
     d = Danforth et al. (2010, ApJ, 720, 976)
     e = Shaw et al. (2013, AJ, 146, 127)
     f = Masetti et al. (2013, A&A, 559, A58)
     g = Sbarufatti et al. (2005, AJ, 129, 559)
  
or else (if left blank) is calculated by the authors (as described in Arsioli et al. 2015, A&A, 579, A34).

Fermi_LAT_Detection
This parameter is populated if there has been a Fermi LAT gamma-ray detection of the object. If it listed in one of the published Fermi LAT Catalogs (1FGL, 2FGL or 3FGL) , its catalogued name is given, while if it was listed as a source in (Arsioli & Chang 2017, A&A, in press, http://adsabs.harvard.edu/abs/2016arXiv160908501A), a value of 'Arsioli et al. 2016' is given. One source (2WHSP J112414.7+234032) has a value of 'X' for this parameter the significance of which is not clear to the HEASARC.

Gamma_Ray_Index
The photon index of the Fermi gamma-ray spectrum of the blazar or blazar candidate, Gamma, corresponding to the energy range 0.1 GeV < E < 100 GeV.

Gamma_Ray_Index_Error
The uncertainty in the photon index of the Fermi gamma-ray spectrum of the blazar or blazar candidate, Gamma, corresponding to the energy range 0.1 GeV < E < 100 GeV.

TwoFHL_Name
The designation of the source in the Second Catalog of Hard Fermi-LAT Sources (2FHL, Ackermann et al. 2016, ApJS, 222, 5, available at the HEASARC as the FERMIFHL table).

Figure_Of_Merit
The Figure of Merit (FOM), was defined in Arsioli et al. (2015, A&A, 579, A34) as the ratio between the synchrotron peak flux (nupeak * f(nupeak) of a given source and that of the faintest blazar in the 1WHSP sample that has already been detected in the TeV band. This parameter was introduced to provide a simple quantitative measure of potential detectability of HSPs by TeV instruments. The FOM parameter is reported for all 2WHSP sources and gives an objective way to assess the likelihood that a given HSP may be detectable as a TeV source. As discussed in Arsioli et al. 2015), relatively high FOM sources (FOM > 0.1) are good targets for observation with the upcoming Cherenkov Telescope Array (CTA).


Contact Person

Questions regarding the WISEHSPCAT database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Thursday, 09-Feb-2017 16:50:42 EST