# Observing proposal for globular clusters in M31

1. Mar 25, 2015

### sketos

Hello,

As part of a course I have been asked to make a observing proposal which aims to detect globular clusters in the bulge of M31. The "virtual" observation will be conducted using the Hubble telescope and the WFC3

To begin with we aim to acquire a sample of globular clusters down to $10^6 M_{\odot}$ in the V-band.
Having a relation for the mass to light ratio i can determine the luminosity in the V-band we are looking for,

$$\frac{M}{L_v}=2.25log(M/M_{\odot})-10.43$$

Then for the relation of of the luminosity and flux density,

$$f_v=C \frac{L_v}{4\pi d^2}$$

i can estimate the desired flux density we are aiming for.

In addition we know that the bulge component dominates in flux of the disk and has a sersic profile with index n=2.2 .

Now my problem is how exactly can i determine what Signal-to-Noise ratio do i need and how i can determine the exposure time of my observation based on these informations. And what resolution do i want for my observation ?

If anyone has worked with that before , I could really use some help .

2. Mar 30, 2015