Hubble Volume Mock Catalogues
The catalogues are available as gzipped files.
Once gunzip'ed they are simple ASCII tables consisting
of a header followed by 6 columns of data.
Column 1: id - An integer identifying the particle in the
orginal Hubble Volume simulation. This is of
little use unless you have access to the 1 Billion
particle Hubble Volume simulation data.
Note that galaxies with the same ID number
(or one that just differs by a sign) are the
same particle in the orginal N-body simulation
and so have identical positions etc. This occurs
as a consequence of how we model biasing and the
selection function. Together these factors give us
a probability, P, that each simulation particle is
to be included as a galaxy in the mock catalogue.
We then draw a random integer, I, from a Poisson
distribution with mean P and include I copies
of the particle in the mock catalogue. Typically,
P<<1 and I=0 or 1, but close to the observer and
in highly biased regions P can approach or exceed
1 and so I>1 can occur resulting in the multiple
copies. For most analysis this causes no problems
at all. However in certain applications it maybe
necessary to either:
i) Randomly perturb the positions of multiple copies
do that they are not exactly coincident. Perturbing by
around 10s of kpc is perfectly valid as this is below
the resolution of the simulation.
ii) Keep only one of the N copies but give it weight
Also note that by applying a low redshift but most
of these duplcated particles can be excluded.
Column 2: ra - Right Ascension in radians in the interval 0 to 2Pi.
(For PSCz we instead list galactic longitude, l .)
Column 3: dec - Declination in radians.
(For PSCz we instead list galactic latitude, b .)
Column 4: mag - Apparent magnitude (B_J for APM/2dF, K for 6dF)
(For PSCz we instead list 60 micron flux in mJy.)
Column 5: zz - Redshift in the CMB frame.
Column 6: zhub - Hubble Flow redshift in the CMB frame. Ie with the
effect of the galaxy's peculiar velocity removed.
Note that you can convert from the CMB to LG frame by
subtracting the velocity of the observer from each galaxy.
The observers velocity is in the direction of the real CMB dipole
ie l=276 deg b=30 deg and its magnitude is given by
vobs=sqrt(vxobs**2+vyobs**2+vzobs**2), where vxobs etc are listed
in the catalogue header. Note that vobs = 625 +/- 25 km/s as
this is one of the constraints applied when choosing the observer.
# ng= 198642
# xobs= 1360.500 yobs= 1307.400 zobs= 739.100 Mpc/h
# vxobs= -345.000 vyobs= 306.000 vzobs= -394.000 km/s
# mockseed= -359078
# omega0= 1.000
# lambda0= 0.000
# sigma_8= 0.600
# basis: 0.24802 -0.21798 0.94391
# -0.90198 -0.40743 0.14291
# 0.35343 -0.88684 -0.29767
# id ra dec mag zz zhub
672624919 3.7005867986427 -0.4782340482322 11.467 0.03182 0.02946
672624913 3.6476975167684 -0.5123586137846 12.467 0.03202 0.02899
672624914 3.6531152419017 -0.5007377672143 11.420 0.03055 0.02822
672624892 3.5813182714546 -0.5173702293422 13.340 0.03078 0.02853