Parameters
Required
- Sky position, galactic, supergalactic, or equatorial (J2000 as 360° decimal) in degrees.
Optional
- Cone (degrees) [default 15°]; plot data points within this cone angle.
- Distance (Mpc); returns model velocity in km/s.
- Velocity (km/s); returns model distance(s) in Mpc – potentially more than one value.
Features
- Model distance – velocity curve (blue) is derived from interpolation of velocities on a grid of distances with grid intervals of 0.2 Mpc at the origin increasing to 1 Mpc intervals at 38 Mpc, the outer limit of the model. The value at a grid point is averaged over the 4 nearest mass points weighted by the inverse square of separation.
- Pause cursor over blue curve for distance and velocity information at chosen location.
- Pause cursor over data points for extra information.
Details
- Data constraining the model are shown as large red circles if distance uncertainties are 5% or less (brown extra large circles for Virgo and Fornax clusters), and as small green circles if uncertainties are over 5% but not more than 15%. Data with larger uncertainties are represented by black plus signs but do not constrain the model.
- Vgsr (km/s) is the galactic standard of rest velocity; referenced to the center of the Galaxy assuming a circular velocity of Sun of 239 km/s plus local solar motion (van der Marel et al. 2012): Vgsr = Vhelio + 11.1 cos(l) cos(b) + 251 sin(l) cos(b) + 7.25 sin(b)
- PGC1 is the Principal Galaxies Catalog identification of the brightest member of the group contributing to the data point (Kourkchi & Tully 2017).
- The H0=75 dashed line is only for reference. Velocities are observed and distances are determined using the scale zero-point described by Tully et al. 2016.
- Click on figure for animation of model orbits.
How to acknowledge this work
References
- Kourkchi & Tully 2017, ApJ, 843, 16
- Shaya et al. 2017, ApJ, 850, 207
- Tully et al 2016, AJ, 152, 50
- Van der Marel et al. 2012, ApJ, 753, 8
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