MassProfile class

Calculates mass vs. radius relations and rotation curves for a given galaxy.

class galaxy.massprofile.MassProfile(gal, com_p=None)

Class to define mass enclosed as a function of radius and circular velocity profiles for a given galaxy and simulation snapshot

Args:

gal (Galaxy object):

The desired galaxy/snap to operate on

com_p (3-vector):

Optional. The position of the disk CoM.

mass_enclosed(radii, ptype=None)

Calculate the mass within a given radius of the CoM for a given type of particle.

Args:

radii (array of distances): spheres to integrate over ptype (int): particle type from (1,2,3), or None for total

Returns:

array of masses, in units of M_sun

mass_enclosed_total(radii)

Calculate the mass within a given radius of the CoM, summed for all types of particle.

Args:

radii (array of distances): spheres to integrate over

Returns:

array of masses, in units of M_sun

halo_mass()

Utility function to get a parameter for Hernquist mass

hernquist_mass(r, a, M_halo=None)

Calculate the mass enclosed for a theoretical profile

Args:

r (Quantity, units of kpc):

distance from center

a (Quantity, units of kpc):

scale radius

M_halo (Quantity, units of M_sun):

total DM mass (optional)

Returns:

Total DM mass enclosed within r (M_sun)

circular_velocity(radii, ptype=None)

Calculate orbital velocity at a given radius from the CoM for a given type of particle.

Args:

radii (array of distances):

circular orbit

ptype (int):

particle type from (1,2,3), or None for total

Returns:

array of circular speeds, in units of km/s

circular_velocity_total(radii)

Syntactic sugar for circular_velocity(radii, ptype=None)

circular_velocity_hernquist(radii, a, M_halo=None)

Theoretical V_circ assuming halo mass follows a Hernquist profile

Args:

radii (array of distances):

circular orbit

a (Quantity, units of kpc):

scale radius

M_halo (Quantity, units of M_sun):

total DM mass (optional)

fit_hernquist_a(r_inner=1, r_outer=30, get_details=False)

Get scipy.optimize to do a non-linear least squares fit to find the best scale radius a for the Hernquist profile.

Args:

r_inner (numeric):

Optional. Minimum radius to consider (implicit kpc). Avoid values < 1 as they cause numeric problems.

r_outer (numeric):

Optional. Maximum radius to consider (implicit kpc).

sersic(R, Re, n, Mtot)

Function that returns Sersic Profile for an Elliptical System (See in-class lab 6)

Input

R:

radius (kpc)

Re:

half mass radius (kpc)

n:

sersic index

Mtot:

total stellar mass

Returns

Surface Brightness profile in Lsun/kpc^2

bulge_Re(R)

Find the radius enclosing half the bulge mass.

Args:

R (array of Quantity):

Radii to consider (kpc)

Returns:

Re (Quantity) :

Radius enclosing half light/mass (kpc)

bulge_total (numeric):

Mass of entire bulge (M_sun, no units)

bulgeI (array of Quantity):

Surface brightness at radii R (kpc^-2), assuming M/L=1

fit_sersic_n(R, Re, bulge_total, bulgeI)

Get scipy.optimize to do a non-linear least squares fit to find the best value of n for a Sersic profile.

Args:

R (array of quantity):

Radii at which to calculate fit (kpc)

Re (Quantity) :

Radius enclosing half light/mass (kpc)

bulge_total (numeric):

Mass of entire bulge (M_sun, no units)

bulgeI (array of Quantity):

Surface brightness at radii R (kpc^-2)

Returns:

best n value and error estimate

density_profile_shell(radii, m, xyz)

Calculates mass density in successive spherical shells

Arg:

radii (array of float):

boundary values beteen shells (implicit kpc, no units)

m (shape (N,) array of float):

particle masses (implicit Msun, no units)

xyz ((3,N) array of float):

particle cartesian coordinates

Returns:

r_annuli: geometric mean of boundaries

(array is one shorter than input radii)

rho: densities (Msun/kpc^3)

(same length as r_annuli)

density_profile_sphere(radii, m, xyz)

Calculates average mass density within successive spherical radii

Arg:

radii (array of float):

boundary values beteen shells (implicit kpc, no units)

m (shape (N,) array of float):

particle masses (implicit Msun, no units)

xyz ((3,N) array of float):

particle cartesian coordinates

Returns:

rho: densities (Msun/kpc^3)

(same length as radii)

virial_radius(r_min=20, r_max=1000, rho_c=None)

Calculates radius where DM density falls to 200x critical density for the universe.

Args:

r_min, r_max (floats)

optional, limits for search (implicit kpc, no units)

rho_c (float or Quantity)

optional, critical density for chosen cosmology

Returns:

r_200 (float): virial radius, implicit kpc

virial_mass(r_200=None, ptype=None)

Mass enclosed by the virial radius