Yes, although the star formation rate in cosmology is usually calculated in a comoving volume, not proper (see, e.g., http://arxiv.org/pdf/1403.0007v2.pdf).

Greg

On Apr 3, 2014, at 11:15 PM, Nathan Goldbaum <nathan12343@gmail.com> wrote:

Hi Geoffrey,

I'm not very familiar with the star formation rate calculator, but if you think there is a bug I'd encourage you to submit a pull request with a fix.

-Nathan

On Thu, Apr 3, 2014 at 6:37 PM, Geoffrey So <gsiisg@gmail.com> wrote:

There seems to be a bug in the star formation rate density calculation routine. The volume is only the real 'proper volume' at the current redshift and not at any other redshifts, because it uses the current redshift in the calculation of proper volume in all redshifts.

#---------------------------------
from yt.mods import *
from yt.analysis_modules.star_analysis.api import *
import pylab

pf=load('HD1200/HD1200')

dd=pf.h.all_data()
sfr = StarFormationRate(pf, data_source=dd, bins=10)
sfr.write_out(name="StarFormationRate.out")
time, lookback, z, Msolyr, MsolyrMpc3, Msol, cumMsol=na.loadtxt('StarFormationRate.out',usecols=(0,1,2,3,4,5,6),skiprows=2,unpack=True)

cMpc3,=pylab.plot(z,Msolyr/(pf['CosmologyComovingBoxSize']/pf['CosmologyHubbleConstantNow'])**3)
currentz,=pylab.plot(z,MsolyrMpc3/(1+pf.current_redshift)**3+1e-5)
Expect,=pylab.plot(z,MsolyrMpc3/(1+z)**3)

pylab.legend([cMpc3,currentz,Expect],
['[s$^{-1}$cMpc$^{-3}$]',
'use only current z to fit',
'Expected to fit'])

pylab.savefig('SFRD.eps')
#---------------------------------

in the file:
yt/analysis_modules/star_analysis/sfr_spectrum.py

line 151:
self.Msol_yr_vol.append(self.mass_bins[i] / \
(self.time_bins_dt[i] * tc / YEAR) / vol)

The vol is a fixed number instead of varying by the redshift, even though the numerator in solar masses per year is from different redshifts.

So I think a couple lines above it should create an empty array of vol
vol = []
In the loop
for i, time…
calculate the right volume vol[i]
Then instead of dividing by the constant vol, divide by vol[i] corresponding to the right redshift.

self.Msol_yr_vol.append(self.mass_bins[i] / \
(self.time_bins_dt[i] * tc / YEAR) / vol[i])

From
G.S.

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----------------------------------

Greg Bryan

Associate Professor of Astronomy

Department of Astronomy, Columbia University

1325 Pupin Physics Laboratories, Mail Code 5246

550 West 120th Street

New York, New York 10027 (USA)

email: gbryan@astro.columbia.edu

phone: +1(212)854-6837

fax : +1(212)854-8121