ACT Data Products - 148/218 GHz Point Source Catalog

Description

This table contains a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 -1700 mJy, and the authors use source spectral indices derived using ACT-only data to divide their sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). They cross-identify 97% of their sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australia Telescope 20-GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, alpha_148-218GHz , of 3.7^+0.62 _-0.86 , and includes both local galaxies and sources with redshifts up to z=6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

The ACT experiment (Swetz et al., 2011, ApJS, 194, 41) is situated on the slopes of Cerro Toco in the Atacama Desert of Chile at an elevation of 5190m. ACT's latitude gives access to both the northern and southern celestial hemispheres. Observations occurred simultaneously in three frequency bands, at 148 GHz (2.0 mm), 218 GHz (1.4 mm) and 277 GHz (1.1 mm) with angular resolutions of roughly 1.4, 1.0 and 0.9 arcminutes, respectively.

The ACT-detected source list contains 169 sources selected at 148 GHz with S/N > 5, spanning two decades in flux density, from 14 to 1700 mJy. The 218 GHz map independently yielded 133 sources with S/N > 5. The combination of these two independent source lists from which the present table was constructed gives a total count of 191 sources, with 110 galaxies detected with S/N > 5 at both frequencies.

Parameters

*Name*
The ACT-S J2000.0 position-based source designation ('ACT-S JHHMMSS+DDMMSS') in the style registered with the Dictionary of Nomenclature of Celestial Objects.

*Source_Flag*
This source flag parameter is set to 'd' if the ACT source is not cross-identified with the catalogs specified in Section 5 of the reference paper.

*RA*
The Right Ascension of the ACT source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.1 seconds of time in the original reference table.

*Dec*
The Declination of the ACT source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.1 arcseconds in the original reference table.

*LII*
The Galactic Longitude of the ACT source.

*BII*
The Galactic Latitude of the ACT source.

*SNR_148_GHz*
The signal-to-noise ratio of the ACT source detection at 148 GHz.

*Meas_Flux_148_GHz*
The 'raw' flux density of the ACT source as estimated directly from the ACT 148-GHz map, as described in Section 3 of the reference paper, in mJy.

*Flux_148_GHz*
The deboosted flux density of the ACT source at 148 GHz, in mJy, derived according to Section 4.2 of the reference paper.

*Flux_148_GHz_Pos_Err*
The 68%-confidence positive error in the deboosted flux density of the ACT source at 148 GHz, in mJy.

*Flux_148_GHz_Neg_Err*
The 68%-confidence negative error in the deboosted flux density of the ACT source at 148 GHz, in mJy.

*SNR_218_GHz*
The signal-to-noise ratio of the ACT source detection at 218 GHz.

*Meas_Flux_218_GHz*
The 'raw' flux density of the ACT source as estimated directly from the ACT 218-GHz map, as described in Section 3 of the reference paper, in mJy.

*Flux_218_GHz*
The deboosted flux density of the ACT source at 218 GHz, in mJy, derived according to Section 4.2 of the reference paper.

*Flux_218_GHz_Pos_Err*
The 68%-confidence positive error in the deboosted flux density of the ACT source at 218 GHz, in mJy.

*Flux_218_GHz_Neg_Err*
The 68%-confidence negative error in the deboosted flux density of the ACT source at 218 GHz, in mJy.

*Meas_Spectral_Index*
The raw spectral index alpha (where S_nu ~ nu^alpha ) of the ACT source between 148 and 218 GHz calculated using the meas_flux_148_ghz and meas_flux_218_ghz parameter values.

*Spectral_Index*
The deboosted spectral index alpha (where S_nu ~ nu^alpha ) of the ACT source between 148 and 218 GHz calculated using the flux_148_ghz and flux_218_ghz parameter values.

*Spectral_Index_Pos_Err*
The positive error in the deboosted spectral index alpha of the ACT source between 148 and 218 GHz.

*Spectral_Index_Neg_Err*
The negative error in the deboosted spectral index alpha of the ACT source between 148 and 218 GHz.

*Source_Class*
The classification of the ACT source according to the spectral index criterion described in section 4.2 of the reference paper, viz:

Sync = synchrotron-dominated sources (the vast majority of which are cross-identified with radio catalogs)

Dust = low-redshift dust-dominated sources with IRAS counterparts (typically ULIRGs) and dust-dominated sources also observed by the South Pole Telescope (SPT), or with no cross-identification, either shown or assumed to be high-redshift star-forming galaxies.

*AT20G_Name*
The AT20G designation of the 20-GHz counterpart to the ACT source, if present in the AT20G catalog, e.g., 'AT20G J001849-511455', or the name of the 20-GHz source counterpart in the 2010 November ATCA follow-up observations made by the authors (if at20g_flag = 'f'), e.g., 'AT20G-f J064150-555103' (this latter naming convention was created by the HEASARC, notice, and is unofficial). This field is left blank if there is no known 20-GHz counterpart.

*AT20G_Flag*
This flag parameter is set to 'f' to indicate that the 20-GHz counterpart is from the 2010 November ATCA follow-up observations made by the authors.

*Flux_20_GHz*
The flux density of the 20-GHz counterpart to the ACT source, in mJy.

*Flux_20_GHz_Error*
The uncertainty in the flux density of the 20-GHz counterpart to the ACT source, in mJy.

Byte-by-byte Description of file: table4.dat

 Bytes Format Units   Label    Explanations

   1-  5  A5    ---     ---      [ACT-S]
   7- 20  A14   ---     ACT-S    ACT-S designation (JHHMMSS+DDMMSS)
      21  A1    ---     n_ACT-S  [d] No cross-identification  Note (1)
  23- 24  I2    h       RAh      Right ascension (J2000)
  26- 27  I2    min     RAm      Right ascension (J2000)
  29- 32  F4.1  s       RAs      Right ascension (J2000)
      34  A1    ---     DE-      Declination sign (J2000)
  35- 36  I2    deg     DEd      Declination (J2000)
  38- 39  I2    arcmin  DEm      Declination (J2000)
  41- 44  F4.1  arcsec  DEs      Declination (J2000)
  46- 50  F5.1  ---     S/N1     [1.7/533] Signal-to-noise ratio at 148GHz
  52- 57  F6.1  mJy     S148m    [4/1721] Flux density as measured directly from
                                  the ACT 148GHz map
  59- 64  F6.1  mJy     S148     [3/1719] Deboosted flux density at 148GHz
  66- 69  F4.1  mJy     E_S148   Error on S148 (upper value)
  71- 74  F4.1  mJy     e_S148   Error on S148 (lower value)
  76- 80  F5.1  ---     S/N2     [1.8/302] Signal-to-noise ratio at 218GHz
  82- 87  F6.1  mJy     S218m    [6/1420] Flux density as measured directly from
                                  the ACT 218GHz map
  89- 94  F6.1  mJy     S218     [6/1420] Deboosted flux density at 218GHz
  96- 99  F4.1  mJy     E_S218   Error on S218 (upper value)
 101-104  F4.1  mJy     e_S218   Error on S218 (lower value)
 106-109  F4.1  ---     alpham   Raw spectral index between 148 and 218GHz
                                 (S(ν)∝να)
 111-114  F4.1  ---     alpha    Deboosted spectral index between 148 and 218GHz
 116-118  F3.1  ---     E_alpha  Error on alpha (upper value)
 120-122  F3.1  ---     e_alpha  Error on alpha (lower value)
 124-127  A4    ---     Type     [Sync Dust] Classification code  Note (2)
 129-142  A14   ---     AT20G    AT20G designation
     143  A1    ---     n_AT20G  [*] Note on AT20G  Note (1)
 145-150  F6.1  mJy     S20      ? Flux density at 20GHz
 152-156  F5.1  mJy     e_S20    ? rms uncertainty on S20

Note (1): Notes as follows:

d = An ACT source not cross-identified with the catalogues specified in Section 5
* = Name from 2010 November follow-up observation catalogue

Note (2): Classification codes are:

Sync = synchrotron-dominated sources (the vast majority of which are 
       cross-identified with radio catalogues)
Dust = low-redshift dust-dominated sources with IRAS counterparts
       (typically ULIRGs) and dust-dominated sources also observed by
       the South Pole Telescope (SPT), or with no cross-identification,
       either shown or assumed to be high-redshift star-forming galaxies.

Additional Details:

The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey", Marsden, Danica, et.al., 2014, MNRAS, 439, 1556 ADS /astro-ph

148 GHz Point Source Catalog

This is a catalog of 157 point sources detected in a 148 GHz data collected by ACT during its 2008 observing season. The sources listed in the catalog were detected as >5.25 sigma peaks in a 455 square-degree subset of the ACT map that had been weighted by the square root of the number of observations and optimally filtered for point source detection. All but three sources have counterparts at other frequencies (ACT-S J034157—515140, ACT-S J004042—511830, and ACT-S J035343—534553). These three sources may be spurious detections. The raw flux density is provided for all sources (column 5). For sources with raw flux density less than 50 mJy, deboosted flux densities (column 6) with errors (columns 7 and 8) are also provided and recommended for external use. The deboosted flux density accounts for the fact that, for a source population for which the counts are a steeply falling function of flux, a source's measured flux density in the presence of noise (i.e., the raw flux density) is likely to be an over-estimate of its intrinsic value.

Col 1 : IAU Name
Col 2 : Right Ascension (J2000)
Col 3 : Declination (J2000)
Col 4 : Signal-to-Noise Ratio
Col 5 : 148 GHz Flux Density (mJy)
Col 6 : Deboosted Flux Density
Col 7 : Positive Error on Deboosted Flux Density (68% c.l.)
Col 8 : Negative Error on Deboosted Flux Density (68% c.l.)
Col 9 : AT20G ID (e.g., Murphy et al. 2010)

Additional Details

• "Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey," Marriage, T.A., et.al. (2010) [eprint arXiv:1007.5256]

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