Automated selection and characterization of emission-line sources in advanced camera for surveys wide field camera grism data

Gerhardt R. Meurer, Z. I. Tsvetanov, C. Gronwall, P. Capak, J. P. Blakeslee, N. Benítez, H. C. Ford, G. D. Illingworth, L. D. Bradley, N. Pirzkal, J. Walsh, R. J. Bouwens, S. Srinivasan

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

We present complementary techniques to find emission-line targets and measure their properties in a semi-automated fashion from grism observations obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST). The first technique is to find all likely sources in a direct image, extract their spectra, and search them for emission lines. The second method is to look for emission-line sources as compact structures in an unsharp masked version of the grism image. Using these methods we identify 46 emission-line targets in the Hubble Deep Field-North using a modest (three-orbit) expenditure of HST observing time. Grism spectroscopy is a powerful tool for efficiently identifying interesting low-luminosity, moderate-redshift emission-line field galaxies. The sources found here have a median i-band (F775W) flux 1.5 mag fainter than the spectroscopic redshift catalog of Cohen et al. They have redshift z ≤ 1.42, and high equivalent widths (typically >100 Å) and are usually less luminous than the characteristic luminosity at the same redshift. The chief obstacle in interpreting the results is line identification, since the majority of sources have a single emission line and the spectral resolution is low. Photometric redshifts are useful for providing a first-guess redshift. However, even at the depth of the state-of-the-art ground-based and HST data used here, photometric errors can result in uncertainties in line identifications, especially for sources with i magnitudes fainter than 24.5 ABmag. Reliable line identification for the faintest emission-line galaxies requires additional ground-based spectroscopy for confirmation. Of particular concern are the faint high-EW [O II] emitters, which could represent a strongly evolving galaxy population if the possibility that they are misidentified lower redshift interlopers can be ruled out.

Original languageEnglish
Pages (from-to)77-95
Number of pages19
JournalAstronomical Journal
Volume134
Issue number1
DOIs
Publication statusPublished - Jul 2007
Externally publishedYes

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cameras
Hubble Space Telescope
galaxies
spectroscopy
luminosity
line source
spectral resolution
catalogs
expenditure
emitters
orbits
method

Keywords

  • Galaxies: distances and redshifts
  • Galaxies: high-redshift
  • Methods: data analysis
  • Surveys
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Automated selection and characterization of emission-line sources in advanced camera for surveys wide field camera grism data. / Meurer, Gerhardt R.; Tsvetanov, Z. I.; Gronwall, C.; Capak, P.; Blakeslee, J. P.; Benítez, N.; Ford, H. C.; Illingworth, G. D.; Bradley, L. D.; Pirzkal, N.; Walsh, J.; Bouwens, R. J.; Srinivasan, S.

In: Astronomical Journal, Vol. 134, No. 1, 07.2007, p. 77-95.

Research output: Contribution to journalArticle

Meurer, GR, Tsvetanov, ZI, Gronwall, C, Capak, P, Blakeslee, JP, Benítez, N, Ford, HC, Illingworth, GD, Bradley, LD, Pirzkal, N, Walsh, J, Bouwens, RJ & Srinivasan, S 2007, 'Automated selection and characterization of emission-line sources in advanced camera for surveys wide field camera grism data', Astronomical Journal, vol. 134, no. 1, pp. 77-95. https://doi.org/10.1086/518228
Meurer, Gerhardt R. ; Tsvetanov, Z. I. ; Gronwall, C. ; Capak, P. ; Blakeslee, J. P. ; Benítez, N. ; Ford, H. C. ; Illingworth, G. D. ; Bradley, L. D. ; Pirzkal, N. ; Walsh, J. ; Bouwens, R. J. ; Srinivasan, S. / Automated selection and characterization of emission-line sources in advanced camera for surveys wide field camera grism data. In: Astronomical Journal. 2007 ; Vol. 134, No. 1. pp. 77-95.
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abstract = "We present complementary techniques to find emission-line targets and measure their properties in a semi-automated fashion from grism observations obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST). The first technique is to find all likely sources in a direct image, extract their spectra, and search them for emission lines. The second method is to look for emission-line sources as compact structures in an unsharp masked version of the grism image. Using these methods we identify 46 emission-line targets in the Hubble Deep Field-North using a modest (three-orbit) expenditure of HST observing time. Grism spectroscopy is a powerful tool for efficiently identifying interesting low-luminosity, moderate-redshift emission-line field galaxies. The sources found here have a median i-band (F775W) flux 1.5 mag fainter than the spectroscopic redshift catalog of Cohen et al. They have redshift z ≤ 1.42, and high equivalent widths (typically >100 {\AA}) and are usually less luminous than the characteristic luminosity at the same redshift. The chief obstacle in interpreting the results is line identification, since the majority of sources have a single emission line and the spectral resolution is low. Photometric redshifts are useful for providing a first-guess redshift. However, even at the depth of the state-of-the-art ground-based and HST data used here, photometric errors can result in uncertainties in line identifications, especially for sources with i magnitudes fainter than 24.5 ABmag. Reliable line identification for the faintest emission-line galaxies requires additional ground-based spectroscopy for confirmation. Of particular concern are the faint high-EW [O II] emitters, which could represent a strongly evolving galaxy population if the possibility that they are misidentified lower redshift interlopers can be ruled out.",
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AU - Capak, P.

AU - Blakeslee, J. P.

AU - Benítez, N.

AU - Ford, H. C.

AU - Illingworth, G. D.

AU - Bradley, L. D.

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