skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A DEEP, WIDE-FIELD, AND PANCHROMATIC VIEW OF 47 Tuc AND THE SMC WITH HST: OBSERVATIONS AND DATA ANALYSIS METHODS

Abstract

In Hubble Space Telescope (HST) Cycle 17, we imaged the well-known globular star cluster 47 Tucanae for 121 orbits using the Wide Field Channel of the Advanced Camera for Surveys (ACS) and both the UV/visible (UVIS) and IR channels of the newly installed Wide Field Camera 3 (WFC3) instrument (GO-11677, PI: H. Richer). This unique data set was obtained to address many scientific questions that demand a very deep, panchromatic, and panoramic view of the cluster's stellar populations. In total, the program obtained over 0.75 Ms of imaging exposure time with the three HST cameras, over a time span of 9 months in 2010. The primary ACS field was imaged in the two broadband filters F606W and F814W, at 13 orientations, for all 121 orbits. The parallel WFC3 imaging provides a panchromatic (0.4-1.7 {mu}m) and contiguous imaging swath over a 250 Degree-Sign azimuthal range at impact radii of 6.5-17.9 pc in 47 Tuc. This imaging totals over 60 arcmin{sup 2} in area and utilizes the F390W and F606W broadband filters on WFC3/UVIS and the F110W and F160W broadband filters on WFC3/IR. In this paper, we describe the observational design of the new survey and one of the methods used tomore » analyze all of the imaging data. This analysis combines over 700 full-frame images taken with the three HST cameras into a handful of ultra-deep, well-sampled combined images in each of the six filters. We discuss in detail the methods used to calculate accurate transformations that provide optimal alignment of the input images, the methods used to perform sky background offsets in the input stack and the flagging of deviant pixels, and the balance reached between the input-pixel drop size onto an output supersampled pixel grid. Careful photometric, morphological, and astrometric measurements are performed on the stacks using iterative PSF-fitting techniques, and reveal unprecedented color-magnitude diagrams of the cluster extending to >30th magnitude in the optical, 29th magnitude in the UV, and 27th magnitude in the IR. The data set provides a characterization of the complete stellar populations of 47 Tuc, extending from the faintest hydrogen-burning dwarfs through the main-sequence and giant branches down to very cool white dwarf remnants in the cluster. The imaging also provides the deepest probe of the stellar populations of the background Small Magellanic Cloud galaxy, resolving low-mass main-sequence dwarfs with M {approx}< 0.2 M{sub Sun }.« less

Authors:
; ;  [1];
  1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
Publication Date:
OSTI Identifier:
22034310
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 143; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; CAMERAS; COLOR; DATA ANALYSIS; FILTERS; HYDROGEN BURNING; IMAGE PROCESSING; IMAGES; INFRARED SPECTRA; ITERATIVE METHODS; MAGELLANIC CLOUDS; MASS; ORBITS; ORIENTATION; PROBES; STAR CLUSTERS; STAR EVOLUTION; TELESCOPES; VISIBLE SPECTRA; WHITE DWARF STARS

Citation Formats

Kalirai, Jason S, Anderson, Jay, Dotter, Aaron, and others, and. A DEEP, WIDE-FIELD, AND PANCHROMATIC VIEW OF 47 Tuc AND THE SMC WITH HST: OBSERVATIONS AND DATA ANALYSIS METHODS. United States: N. p., 2012. Web. doi:10.1088/0004-6256/143/1/11.
Kalirai, Jason S, Anderson, Jay, Dotter, Aaron, & others, and. A DEEP, WIDE-FIELD, AND PANCHROMATIC VIEW OF 47 Tuc AND THE SMC WITH HST: OBSERVATIONS AND DATA ANALYSIS METHODS. United States. https://doi.org/10.1088/0004-6256/143/1/11
Kalirai, Jason S, Anderson, Jay, Dotter, Aaron, and others, and. 2012. "A DEEP, WIDE-FIELD, AND PANCHROMATIC VIEW OF 47 Tuc AND THE SMC WITH HST: OBSERVATIONS AND DATA ANALYSIS METHODS". United States. https://doi.org/10.1088/0004-6256/143/1/11.
@article{osti_22034310,
title = {A DEEP, WIDE-FIELD, AND PANCHROMATIC VIEW OF 47 Tuc AND THE SMC WITH HST: OBSERVATIONS AND DATA ANALYSIS METHODS},
author = {Kalirai, Jason S and Anderson, Jay and Dotter, Aaron and others, and},
abstractNote = {In Hubble Space Telescope (HST) Cycle 17, we imaged the well-known globular star cluster 47 Tucanae for 121 orbits using the Wide Field Channel of the Advanced Camera for Surveys (ACS) and both the UV/visible (UVIS) and IR channels of the newly installed Wide Field Camera 3 (WFC3) instrument (GO-11677, PI: H. Richer). This unique data set was obtained to address many scientific questions that demand a very deep, panchromatic, and panoramic view of the cluster's stellar populations. In total, the program obtained over 0.75 Ms of imaging exposure time with the three HST cameras, over a time span of 9 months in 2010. The primary ACS field was imaged in the two broadband filters F606W and F814W, at 13 orientations, for all 121 orbits. The parallel WFC3 imaging provides a panchromatic (0.4-1.7 {mu}m) and contiguous imaging swath over a 250 Degree-Sign azimuthal range at impact radii of 6.5-17.9 pc in 47 Tuc. This imaging totals over 60 arcmin{sup 2} in area and utilizes the F390W and F606W broadband filters on WFC3/UVIS and the F110W and F160W broadband filters on WFC3/IR. In this paper, we describe the observational design of the new survey and one of the methods used to analyze all of the imaging data. This analysis combines over 700 full-frame images taken with the three HST cameras into a handful of ultra-deep, well-sampled combined images in each of the six filters. We discuss in detail the methods used to calculate accurate transformations that provide optimal alignment of the input images, the methods used to perform sky background offsets in the input stack and the flagging of deviant pixels, and the balance reached between the input-pixel drop size onto an output supersampled pixel grid. Careful photometric, morphological, and astrometric measurements are performed on the stacks using iterative PSF-fitting techniques, and reveal unprecedented color-magnitude diagrams of the cluster extending to >30th magnitude in the optical, 29th magnitude in the UV, and 27th magnitude in the IR. The data set provides a characterization of the complete stellar populations of 47 Tuc, extending from the faintest hydrogen-burning dwarfs through the main-sequence and giant branches down to very cool white dwarf remnants in the cluster. The imaging also provides the deepest probe of the stellar populations of the background Small Magellanic Cloud galaxy, resolving low-mass main-sequence dwarfs with M {approx}< 0.2 M{sub Sun }.},
doi = {10.1088/0004-6256/143/1/11},
url = {https://www.osti.gov/biblio/22034310}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 1,
volume = 143,
place = {United States},
year = {Sun Jan 15 00:00:00 EST 2012},
month = {Sun Jan 15 00:00:00 EST 2012}
}