Index Key to Source Characterization Table
Name & Position
- name is either the 2MASS designation or the common NED name (for LGA galaxies). The designation is derived from the J2000 sexigesimal coordinates of the source and has the form HHMMSSSS+/-DDMMSSS, where HH are the hours of right ascension, MM the RA minutes and SSS are the deci-seconds of RA. DD are the degrees in declination, MM are DEC minutes and SS the declination seconds. Note that both the RA deci-seconds of time and DEC seconds of arc are truncated rather than rounded, per the IAU recommendation.
- RA is the right ascension in J2000 (deg)
- Dec is the declination in J2000 (deg)
Orientation & Shape
- r_3sig is the Ks-band 3-sigma isophotal radius used to fit ellipse and determine orientation
- sup_ba is the axis-ratio of J+H+K (super) image at the 3-sigma isophote
- sup_pa is the position angle of J+H+K (super) isophote (east of north)
- j_ba is the J-band axis-ratio as measured from the 3-sigma isophote
- j_phi is the J-band position angle as measured from the 3-sigma isophote
- h_ba is the H-band axis-ratio as measured from the 3-sigma isophote
- h_phi is the H-band position angle as measured from the 3-sigma isophote
- k_ba is the Ks-band axis-ratio as measured from the 3-sigma isophote
- k_phi is the Ks-band position angle as measured from the 3-sigma isophote
- sup_chif_ellf is the goodness of fit to the J+H+Ks combined image 3-sigma isophote
- j_chif_ellf is the goodness of fit to the J-band 3-sigma isophote
- h_chif_ellf is the goodness of fit to the H-band 3-sigma isophote
- k_chif_ellf is the goodness of fit to the Ks-band 3-sigma isophote
Additional information:
Image Parameters
Small cut-outs of the non-compressed J, H and Ks Atlas Images around each of the XSC sources in the AllSky Release are available on-line. The Postage Stamp Image sizes are scaled to the size of the object, ranging from 21´´ × 21´´ for the faintest galaxies (Ks > 13 mag) to a maximum of 301´´ × 301´´. For galaxies larger than 301´´, it is best to use the 2MASS Large Galaxy ATLAS, which consists of full mosaiced images and photometry of the largest galaxies in the sky.
The 2MASS Extended Source Postage Stamp Images are 6-dimensional FITS image cubes. Each plane contains the J, H and Ks 2MASS image data, respectively, with stars removed from the final 3 planes. The near-infrared background emission has been subtracted from each image plane. Positional and photometric calibration information are included in the image header. An example header is given here.
Isophotal Photometry
The isophotal measurements are set at the 20 mag per arcsec2 isophote at Ks (corresponding to roughly 1-sigma of the background RMS), using both circular and elliptically shape-fit apertures.
- r_k20fe is the Ks-band 20 mag/arcsec2 elliptical radius (arcsec)
- j_m_k20fe is the J-band mag using the r_k20fe elliptical aperture
- j_msig_k20fe is the mag uncertainty in j_m_k20fe
- j_flg_k20fe is the J-band confusion flag (0 == nominal; 1 = stellar contamination)
- h_m_k20fe is the H-band mag using the r_k20fe elliptical aperture
- h_msig_k20fe is the mag uncertainty in h_m_k20fe
- h_flg_k20fe is the H-band confusion flag (0 == nominal; 1 = stellar contamination)
- k_m_k20fe is the Ks-band mag using the r_k20fe elliptical aperture
- k_msig_k20fe is the mag uncertainty in k_m_k20fe
- k_flg_k20fe is the Ks-band confusion flag (0 == nominal; 1 = stellar contamination)
- J-K is the J-Ks color using the isophotal aperture
- J-K_sig is the mag uncertainty in J-K
Additional information:
7" Radius Circular Aperture Photometry
- j_m_7 is the J-band 7" aperture photometry
- j_msig_7 is the uncertainty in j_m_7
- j_flg_7 is the J-band confusion flag (0 == nominal; 1 = stellar contamination)
- h_m_7 is the H-band 7" aperture photometry
- h_msig_7 is the uncertainty in h_m_7
- h_flg_7 is the H-band confusion flag (0 == nominal; 1 = stellar contamination)
- k_m_7 is the Ks-band 7" aperture photometry
- k_msig_7 is the uncertainty in k_m_7
- k_flg_7 is the K-band confusion flag (0 == nominal; 1 = stellar contamination)
Kron Photometry
- r_fe is the Kron elliptical aperture radius (arcsec)
- j_m_e is the J-band Kron mag
- j_msig_e is the mag uncertainty in j_m_e
- j_flg_e is the J-band confusion flag (0 == nominal; 1 = stellar contamination)
- h_m_e is the H-band Kron mag
- h_msig_e is the mag uncertainty in h_m_e
- h_flg_e is the H-band confusion flag (0 == nominal; 1 = stellar contamination)
- k_m_e is the Ks-band Kron mag
- k_msig_e is the mag uncertainty in k_m_e
- k_flg_e is the Ks-band confusion flag (0 == nominal; 1 = stellar contamination)
Additional information:
"Total" Photometry
The "total" aperture consists of the isophotal aperture plus the integration of the surface brightness profile that extends from the isophotal aperture out to ~4 disk scale lengths (i.e., well below the 1-sigma RMS noise level). With this curve of growth technique, an additional 10-20% of the galaxy flux is recovered (depending on the type of galaxy).
- r_ext is the "total" elliptical aperture radius (arcsec), via extrapolation of the radial SB profile
- j_m_ext is the J-band total mag
- j_msig_ext is the mag uncertainty in j_m_ext
- j_flg_ext is the J-band confusion flag (0 == nominal; 1 = stellar contamination)
- j_pchi is the reduced Χ2(chi-square) of the fit to the J-band SB profile
- h_m_ext is the H-band total mag
- h_msig_ext is the mag uncertainty in h_m_ext
- h_flg_ext is the H-band confusion flag (0 == nominal; 1 = stellar contamination)
- h_pchi is the reduced Χ2(chi-square) of the fit to the H-band SB profile
- k_m_ext is the Ks-band total mag
- k_msig_ext is the mag uncertainty in k_m_ext
- k_flg_ext is the Ks-band confusion flag (0 == nominal; 1 = stellar contamination)
- k_pchi is the reduced Χ2(chi-square) of the fit to the K-band SB profile
Additional information:
Half-Light "Effective" Size, Surface Brightness & Concentration Index
- j_r_eff is the J-band half-light radius (arcsec)
- j_mnsurfb_eff is the J-band half-light surface brightness (mag/arcsec2)
- j_con_indx is the J-band concentration index
- h_r_eff is the H-band half-light radius (arcsec)
- h_mnsurfb_eff is the H-band half-light surface brightness (mag/arcsec2)
- h_con_indx is the H-band concentration index
- k_r_eff is the Ks-band half-light radius (arcsec)
- k_mnsurfb_eff is the Ks-band half-light surface brightness (mag/arcsec2)
- k_con_indx is the Ks-band concentration index
Additional information:
Profile Fit Parameters
- j_alpha is J-band radial SB profile fit scale length (arcsec)
- j_beta is J-band radial SB profile fit modulation index
- h_alpha is H-band radial SB profile fit scale length (arcsec)
- h_beta is H-band radial SB profile fit modulation index
- k_alpha is Ks-band radial SB profile fit scale length (arcsec)
- k_beta is Ks-band radial SB profile fit modulation index
Additional information: