search

kperezsa / BNS-MergerRates

1 stars 0 forks source link

Refinining calculation of rate per M_sun per year in dwarf galaxies #1

Open soares-santos opened 7 years ago

soares-santos commented 7 years ago

Following up on the discussion during @kperezsa presentation yesterday. Currently, the rate calculation is:

r = N_obs / (Mstar_obs.sum() * dt) # in units of [M_sun^-1 * year^-1]

where

N_obs = 1 is the number of dwarf galaxies showing r-process enhancement consistent with one BNS event.

Mstar.sum() = Ngals_obs * (Mstar of RetII) = 8 * (2.6x1e3) M_sun is the sum of the stellar masses of the dwarf galaxies for which observations of the r-process element abundance exists.

dt = age of RetII = 10 Gyr is the timescale

We want to improve the estimate of those two numbers and put error bars in them.

For Mstar.sum() the idea is to get the numbers from the literature and sum them directly (@kadrlica, can you send again the references containing these numbers?

For dt, conservatively we could say that dt is the average age of the dwarf galaxies (~10 Gyr for RetII), Perhaps something like the timescale of evolution of the massive stars that are progenitors of the observed event (~3Gyr) would be best.

kperezsa commented 7 years ago

@soares-santos Alex sent me a paper with the list of dwarf galaxies that have had high resolution spectroscopy (fig 3 of Nagasawa et al, 2015 paper). I plan on looking up their stellar masses in the papers referenced in the footnote of the figure.

kadrlica commented 7 years ago

I think you are asking about a reference for the stellar mass of Ret II? That is Table 2 of Bechtol et al. 2015. It assumes a Chabrier IMF, but the choice of IMF can give a factors of ~2 uncertainty (at least for the faintest dwarfs). This is shown in Table 1 of Martin et al. 2008 where he compares Salpeter and Kroupa IMFs.