Spectral Frames
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 | $$V=c\frac{(1-(\frac{f_v}{f_0})^2)}{(1+(\frac{f_v}{f_0})^2)}$$ |