Searching for 2MASS All-Sky Atlas Images#

This notebook tutorial demonstrates the process of querying IRSA’s Simple Image Access (SIA) service for the 2MASS All-Sky Atlas, making a cutout image (thumbnail), and displaying the cutout.

Learning Goals#

By the end of this tutorial, you will:

Learn how to search the NASA Astronomical Virtual Observatory Directory web portal for a service that provides access to IRSA’s 2MASS images.
Use the Python pyvo package to identify which of IRSA’s 2MASS images cover a specified coordinate.
Download one of the identified images.
Create and display a cutout of the downloaded image.

Introduction#

The Two Micron All Sky Survey (2MASS) project uniformly scanned the entire sky in three near-infrared bands to detect and characterize point sources brighter than about 1 mJy in each band, with signal-to-noise ratio (SNR) greater than 10. More information about 2MASS can be found at:

https://irsa.ipac.caltech.edu/Missions/2mass.html

The NASA/IPAC Infrared Science Archive (IRSA) at Caltech is the archive for 2MASS images and catalogs. The 2MASS images that are the subject of this tutorial are made accessible via the International Virtual Observatory Alliance (IVOA) Simple Image Access (SIA) protocol. IRSA’s 2MASS SIA service is registered in the NASA Astronomical Virtual Observatory (NAVO) Directory. Based on the registered information, the Python package pyvo can be used to query the 2MASS SIA service for a list of images that meet specified criteria, and standard Python libraries can be used to download and manipulate the images. Other datasets at IRSA are available through other SIA services:

https://irsa.ipac.caltech.edu/docs/program_interface/api_images.html

Imports#

pyvo for querying IRSA’s 2MASS SIA service
astropy.coordinates for defining coordinates
astropy.nddata for creating an image cutout
astropy.wcs for interpreting the World Coordinate System header keywords of a fits file
astropy.units for attaching units to numbers passed to the SIA service
matplotlib.pyplot for plotting
astropy.utils.data for downloading files
astropy.io to manipulate FITS files

import pyvo as vo
from astropy.coordinates import SkyCoord
from astropy.nddata import Cutout2D
from astropy.wcs import WCS
import astropy.units as u
import matplotlib.pyplot as plt
from astropy.utils.data import download_file
from astropy.io import fits

Section 1 - Setup#

Set images to display in the notebook

%matplotlib inline

Define coordinates of a bright star

ra = 314.30417
dec = 77.595559
pos = SkyCoord(ra=ra, dec=dec, unit='deg')

Section 2 - Lookup and define a service for 2MASS images#

Start at STScI VAO Registry at https://vao.stsci.edu/keyword-search/

Limit by Publisher “NASA/IPAC Infrared Science Archive” and Capability Type “Simple Image Access Protocol” then search on “2MASS”

Locate the SIA URL https://irsa.ipac.caltech.edu/cgi-bin/2MASS/IM/nph-im_sia?type=at&ds=asky&

twomass_service = vo.dal.SIAService("https://irsa.ipac.caltech.edu/cgi-bin/2MASS/IM/nph-im_sia?type=at&ds=asky&")

Section 3 - Search the service#

Search for images covering within 1 arcsecond of the star

im_table = twomass_service.search(pos=pos, size=1.0*u.arcsec)

Examine the table of images that is returned

im_table.to_table()

Table length=12

name	download	center_ra	center_dec	naxes	naxis	scale	format	crpix	crval	crota2	band	bref	bhi	blo	pers_art	glint_art	type	dataset	pixflags	id	scntr	date	hem	scan	image	ut_date	coadd_key	seesh	magzp	msnr10	bin
		deg	deg			deg			deg	deg		meters	meters	meters														arcseconds
object	object	float64	float64	int32	object	object	object	object	object	float64	object	float64	float64	float64	object	object	object	object	object	object	object	object	object	int32	int32	object	int32	float64	float64	float64	int32
All-Sky Release Survey J-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=000616n&scan=060&name=ji0600256.fits	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	J	1.235e-06	1.404e-06	1.066e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.63965	20.8408	16.567	201030300
All-Sky Release Survey J-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1388256&band=J	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	J	1.235e-06	1.404e-06	1.066e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.63965	20.8408	16.567	201030300
All-Sky Release Survey H-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=000616n&scan=060&name=hi0600256.fits	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	H	1.662e-06	1.924e-06	1.4e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.6083	20.3352	15.476	201030300
All-Sky Release Survey H-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1388256&band=H	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	H	1.662e-06	1.924e-06	1.4e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.6083	20.3352	15.476	201030300
All-Sky Release Survey K-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=000616n&scan=060&name=ki0600256.fits	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	K	2.159e-06	2.434e-06	1.884e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.70235	20.0396	14.709	201030300
All-Sky Release Survey K-Band Atlas Image: 000616 n 060 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1388256&band=K	314.5216579	77.65369905	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.5216579 77.65369905]	-0.03194277641	K	2.159e-06	2.434e-06	1.884e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=000616&hem=n&scan=060	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=000616&hem=n&scan=060	A	asky	CZ	null	null	000616	n	60	256	000616	1388256	2.70235	20.0396	14.709	201030300
All-Sky Release Survey J-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=001129n&scan=019&name=ji0190256.fits	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	J	1.235e-06	1.404e-06	1.066e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.671	20.9334	16.406	201030220
All-Sky Release Survey J-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1528372&band=J	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	J	1.235e-06	1.404e-06	1.066e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.671	20.9334	16.406	201030220
All-Sky Release Survey H-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=001129n&scan=019&name=hi0190256.fits	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	H	1.662e-06	1.924e-06	1.4e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.6083	20.3395	15.132	201030220
All-Sky Release Survey H-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1528372&band=H	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	H	1.662e-06	1.924e-06	1.4e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.6083	20.3395	15.132	201030220
All-Sky Release Survey K-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=001129n&scan=019&name=ki0190256.fits	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	image/fits	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	K	2.159e-06	2.434e-06	1.884e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.63965	20.0656	14.862	201030220
All-Sky Release Survey K-Band Atlas Image: 001129 n 019 0256	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im_key?ds=asky&key=1528372&band=K	314.1043524	77.65121426	2	[512 1024]	[-0.0002777777845 0.0002777777845]	text/html	[256.5 512.5]	[314.1043524 77.65121426]	0.04799351843	K	2.159e-06	2.434e-06	1.884e-06	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=pers&ds=asky&date=001129&hem=n&scan=019	https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-art?arttype=glint&ds=asky&date=001129&hem=n&scan=019	A	asky	CZ	null	null	001129	n	19	256	001129	1528372	2.63965	20.0656	14.862	201030220

Section 4 - Locate and download an image of interest#

Locate the first H-band image and display its URL

for i in range(len(im_table)):
    if im_table[i]['band'] == 'H':
        break
print(im_table[i].getdataurl())

https://irsa.ipac.caltech.edu:443/cgi-bin/2MASS/IM/nph-im?ds=asky&atdir=/ti08&dh=000616n&scan=060&name=hi0600256.fits

Download the image and open it in Astropy

fname = download_file(im_table[i].getdataurl(), cache=True)
image1 = fits.open(fname)

Section 5 - Extract a cutout and plot it#

wcs = WCS(image1[0].header)

cutout = Cutout2D(image1[0].data, pos, (60, 60), wcs=wcs)
wcs = cutout.wcs

fig = plt.figure()

ax = fig.add_subplot(1, 1, 1, projection=wcs)
ax.imshow(cutout.data, cmap='gray_r', origin='lower',
          vmax = 1000)
ax.scatter(ra, dec, transform=ax.get_transform('fk5'), s=500, edgecolor='red', facecolor='none')

<matplotlib.collections.PathCollection at 0x7fa9c0869290>

../../_images/cea9d07ec8117237effa4af416ea74e232b9a1935cb0ab5d636e39a471c22295.png

Exercise#

Repeat the steps above to retrieve a cutout from the AllWISE Atlas images

About this notebook#

Author: David Shupe, IRSA Scientist, and the IRSA Science Team

Updated On: 2023-02-16

Contact: irsasupport@ipac.caltech.edu or https://jira.ipac.caltech.edu/irsasupport

Citations#

If you use astropy for published research, please cite the authors. Follow these links for more information about citing astropy:

Citing astropy

If you use 2MASS data in published research, please cite the canonical paper Skrutskie et al (2006), and include the following standard acknowledgment:

“This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.”

Please also cite the doi for the 2MASS All-Sky Atlas Image Service at https://www.ipac.caltech.edu/doi/irsa/10.26131/IRSA121

Searching for 2MASS All-Sky Atlas Images

Contents