laurence
c6299f41ab
Preparing to merge this repository into a combined astrophotography repo. session-scripts/ becomes pipeline/ because the scripts import layout.py from their own directory and must stay together, and because 'pipeline' says what it is rather than how it came about. observing/ stays at the top level: observing plans are not processing code.
91 lines
3.1 KiB
Python
91 lines
3.1 KiB
Python
"""Fetch a published globular cluster catalogue for NGC 5128 (Centaurus A) from VizieR.
|
|
|
|
Primary catalogue: J/MNRAS/469/3444 table "gc" -- Taylor, Puzia, Ferrarez et al. 2017,
|
|
MNRAS 469, 3444, "Survey of Centaurus A's Baryonic Structures (SCABS) II":
|
|
3210 globular cluster candidates with ugriz photometry over ~1.55 deg^2 centred on Cen A.
|
|
|
|
Fallback: J/AJ/143/84 (Harris+ 2012, 833 new GC candidates).
|
|
|
|
Writes _cena_gc_ref.npz with keys:
|
|
ra, dec : degrees, J2000 (ICRS)
|
|
vmag : Johnson V estimated from SDSS g,r via Lupton (2005):
|
|
V = g - 0.5784*(g-r) - 0.0038
|
|
gmag,rmag: SDSS-like g and r from the source catalogue (NaN where missing)
|
|
prob : Taylor+ 2017 GC membership probability (0-1), higher = more likely a GC
|
|
"""
|
|
import numpy as np
|
|
from astroquery.vizier import Vizier
|
|
from astropy.coordinates import SkyCoord
|
|
import astropy.units as u
|
|
|
|
import layout
|
|
|
|
OUT = layout.path("_cena_gc_ref.npz")
|
|
RA0, DEC0 = 201.365, -43.019
|
|
# field half-widths in arcmin for a 43' x 29' frame
|
|
HW_RA, HW_DEC = 21.5, 14.5
|
|
|
|
|
|
def col(t, name):
|
|
if name not in t.colnames:
|
|
return None
|
|
return np.ma.filled(np.ma.asarray(t[name]).astype(float), np.nan)
|
|
|
|
|
|
def report(ra, dec, label):
|
|
dra = (ra - RA0) * np.cos(np.radians(dec)) * 60.0
|
|
dde = (dec - DEC0) * 60.0
|
|
sep = np.hypot(dra, dde)
|
|
infield = (np.abs(dra) <= HW_RA) & (np.abs(dde) <= HW_DEC)
|
|
print(f" {label}: {len(ra)} rows")
|
|
print(f" RA {ra.min():.4f} .. {ra.max():.4f} "
|
|
f"(span {(ra.max()-ra.min())*np.cos(np.radians(DEC0))*60:.1f}')")
|
|
print(f" Dec {dec.min():.4f} .. {dec.max():.4f} "
|
|
f"(span {(dec.max()-dec.min())*60:.1f}')")
|
|
print(f" sep from centre: median {np.median(sep):.1f}' max {sep.max():.1f}'")
|
|
print(f" inside 43'x29' field: {infield.sum()}")
|
|
return infield
|
|
|
|
|
|
def main():
|
|
v = Vizier(row_limit=-1)
|
|
cid, tname = "J/MNRAS/469/3444", "J/MNRAS/469/3444/gc"
|
|
print(f"Fetching {tname} (Taylor+ 2017, SCABS II)")
|
|
try:
|
|
tabs = v.get_catalogs(cid)
|
|
t = [x for x in tabs if x.meta.get("name") == tname][0]
|
|
except Exception as e:
|
|
print(f" FAILED: {e}")
|
|
return 1
|
|
|
|
# RAJ2000/DEJ2000 are sexagesimal strings in this table
|
|
sc = SkyCoord(np.asarray(t["RAJ2000"], str), np.asarray(t["DEJ2000"], str),
|
|
unit=(u.hourangle, u.deg))
|
|
ra = sc.ra.deg
|
|
dec = sc.dec.deg
|
|
g = col(t, "gmag")
|
|
r = col(t, "rmag")
|
|
prob = col(t, "Prob")
|
|
|
|
good = np.isfinite(ra) & np.isfinite(dec)
|
|
ra, dec, g, r, prob = ra[good], dec[good], g[good], r[good], prob[good]
|
|
|
|
# -1.0 is the catalogue's "no photometry" sentinel -> NaN
|
|
g = np.where(g <= 0, np.nan, g)
|
|
r = np.where(r <= 0, np.nan, r)
|
|
|
|
# Lupton (2005) SDSS -> Johnson V
|
|
vmag = g - 0.5784 * (g - r) - 0.0038
|
|
|
|
report(ra, dec, tname)
|
|
print(f" vmag finite: {np.isfinite(vmag).sum()} "
|
|
f"range {np.nanmin(vmag):.2f} .. {np.nanmax(vmag):.2f}")
|
|
print(f" prob >=0.5: {(prob >= 0.5).sum()} >=0.9: {(prob >= 0.9).sum()}")
|
|
|
|
np.savez(OUT, ra=ra, dec=dec, vmag=vmag, gmag=g, rmag=r, prob=prob)
|
|
print(f"WROTE {OUT}")
|
|
return 0
|
|
|
|
|
|
if __name__ == "__main__":
|
|
raise SystemExit(main())
|