Spectral Frames

Spectral Frames supported in CASA

Spectral Frames

CASA supported spectral frames:

Frame Description Definition  
REST           rest frequency               Lab frame or source frame; cannot be converted to any other frame
LSRK LSR as a kinematic (radio) definition  (J2000) based on average velocity of stars in the Solar neighborhood 20km/s in direction of RA, Dec - [270,+30] deg (B1900.0) (Gordon 1975 [1] )
LSRD Local Standard of Rest (J2000), dynamical, IAU definition. Solar peculiar velocity in the reference frame of a circular orbit about the Galactic Center, based on average velocity of stars in the Solar neighborhood and solar peculiar motion U$\odot$=9kms/s, V$\odot$=12km/s,W$\odot$=7km/s. Or 16.552945km/s  towards l,b = 53.13, +25.02 deg (Delhaye 1965 [2])
BARY Solar System Baryceneter (J2000)  
GEO Geocentric, referenced to the Earth's center  
TOPO Topocentric Local observatory frame, fixed in observing frequency, no doppler tracking
GALACTO Galactocentric (J2000), referenced to dynamical center of the Galaxy 220 km/s in the direction l,b = 270, +0 deg.  (Kerr and Lynden-Bell 1986  [3])
LGROUP Mean motion of Local Group Galaxies with respect to its bary center 308km/s towards l,b = 105,-7
CMB Cosmic Microwave Background, COBE measurements of dipole anisotropy 369.5km/s towards l,b = 264.4,48.4. (Kogut et al. 1993 [4])
Undefined    

 

 
Citation Number 1
Citation Text Gordon 1975: "Methods of Experimental Physics: Volume 12: Astrophysics, Part C: Radio Observations", ed. M.L.Meeks, Academic Press 1976
Citation Number 2
Citation Text Delhaye 1965 (ADS)

 

Citation Number 3
Citation Text Kerr F. J. & Lynden-Bell D. 1986 MNRAS, 221, 1023 (ADS)
Citation Number 4
Citation Text Kogut A. et al. 1993 (ADS)

 

 Doppler Types

CASA supported Doppler types (velocity conventions) where $f_v$ is the observed frequency and $f_0$ is the rest frame frequency of a given lineand positive velocity V is increasing away from the observer:

Name Description
RADIO $$V = c \frac{(f_0 - f_v)}{f_0}$$
Z $$V=cz$$  $$z = \frac{(f_0 - f_v)}{f_v}$$
RATIO $$V=c(\frac{f_v}{f_o})$$
BETA $$V=c\frac{(1-(\frac{f_v}{f_0})^2)}{(1+(\frac{f_v}{f_0})^2)}$$
GAMMA $$ V=c\frac{(1 + (\frac{f_v}{f_0})^2)}{2\frac{f_v}{f_0}}$$
OPTICAL $$V= c\frac{(f_0 - f_v)}{f_v}$$
TRUE $$V=c\frac{(1-(\frac{f_v}{f_0})^2)}{(1+(\frac{f_v}{f_0})^2)}$$
RELATIVISTIC $$V=c\frac{(1-(\frac{f_v}{f_0})^2)}{(1+(\frac{f_v}{f_0})^2)}$$