How do I find how many galaxies MaNGA has observed?

Astropy primer for working with table data

import numpy as np
from astropy.io import fits

drpall = fits.open('drpall-v2_4_3.fits')
tbdata = drpall[1].data

# Print column names
tbdata.columns.names

Find the redshift of a galaxy:

ind = np.where(tbdata['mangaid'] == '12-193481')
print('redshift =', tbdata['nsa_z'][ind][0])

Find galaxies that match a specific ancillary catalog:

# select the column for the MaNGA Target 3 bitmask
targets = tbdata['mngtarg3']

# select rows from the Dwarf Galaxies with MaNGA ancillary catalog (which is bit 14)
dwarf_indices = np.where(targets & 1 << 14)[0]
print(dwarf_indices)
array([  750,   943,  1709,  7457,  7488,  7489,  7518,  7591,  7671,
        8003,  8179,  8448,  8464,  8866,  9198,  9423,  9674,  9687,
        9996, 10757, 11442])

Identifying unique galaxies:

# Find all datacubes 
cube_bools = (data['mngtarg1'] != 0) | (data['mngtarg3'] != 0))
cubes = data[cube_bools]

# Find galaxies excluding those from the Coma, IC342, M31 ancillary programs (bits 19,20,21)
targ3 = data['mngtarg3']
galaxies = data[cube_bools & ((targ3 & 1<<19) == 0) & ((targ3 & 1<<20) == 0) & ((targ3 & 1<<21) == 0)]
print('Number of galaxies', len(galaxies))

# Get unique galaxies
uniq_vals, uniq_idx=np.unique(galaxies['mangaid'], return_index=True)
uniq_galaxies = galaxies[uniq_idx]
print('Unique galaxies', len(uniq_galaxies))

The drpall file can be read in using for example MRDFITS. This will put the data into an IDL structure.

t=mrdfits('drpall-v2_4_3.fits',1,hdr)

; Print column names
help,t,/str

Find the redshift of a galaxy:

ind = where(t.mangaid eq '12-193481')
print,'redshift =', t[ind].nsa_z

Identifying unique galaxies:

; Find the indices of datacubes 
cube_bools = (t.mngtarg1 ne 0) or (t.mngtarg3 ne 0)

; Select only datacubes
cubes = t[where(cube_bools)]
print,'Number of data cubes: ', n_elements(cubes) 

; Find galaxies excluding those from the Coma, IC342, M31 ancillary programs (bits 19,20,21)
galaxies = t[where(cube_bools and ((t.mngtarg3 and 2L^19L+2L^20L+2L^21) eq 0))]

; Select unique galaxies
mangaid = galaxies.mangaid
uqmangaid = mangaid[uniq(mangaid[sort(mangaid)])]
print,'Number of unique galaxies: ', n_elements(uqmangaid) 

Select Main Sample Galaxies

To select the Main Sample galaxies (Primary + Secondary + Color Enhanced samples), we need to download the DR15 drpall file file and put it in the expected $SAS_BASE_DIR directory. For more information on the location of your SAS_BASE_DIR environment variable, see the Marvin documentation.

Let’s open the DRPall file:

from marvin import config
from marvin.utils.general.general import get_drpall_table

config.setRelease('DR15')
data = get_drpall_table()

The Main Sample consists of the Primary, Secondary, and Color-Enhanced Samples, which correspond to MNGTARG1 bits 10, 11, and 12, respectively.

import numpy as np
primary        = data['mngtarg1'] & 2**10                                 
secondary      = data['mngtarg1'] & 2**11                                 
color_enhanced = data['mngtarg1'] & 2**12                                 

main_sample = np.logical_or.reduce((primary, secondary, color_enhanced)) 

plateifus = data['plateifu'][main_sample]

The drpAll file exists as a table in CAS. You can query the drpall table under the Query tab in CASjobs. For example, to find all galaxies with redshift > 0.05 and stellar mass <1e10:

SELECT  
mangaid, objra, objdec, nsa_z, nsa_sersic_mass 	
FROM dbo.mangaDrpAll	
where nsa_z > 0.05 and nsa_sersic_mass < 1e10