The distance and metallicity of the newly discovered, nearby irregular galaxy HIZSS 3

David R. Silva, Philip Massey, Kathleen D Eastwood, P. A. Henning

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

HIZSS 3 is an H I source in the Zone of Avoidance. Its radio characteristics are consistent with it being a previously unknown, nearby (∼1.8 Mpc), low-mass dwarf irregular (dIrr) galaxy. Optical observations have shown that it contains a modest H n region, but they failed to reveal a resolved stellar population. New spectroscopic observations of the H n region obtained at the MMT Observatory are presented here. They are used to derive the line-of-sight extinction [E(B - V) = 1.41 ± 0.04] and gas metallicity (log O/H + 12 ∼ 7.8) of the H II region. New near-IR imaging observations obtained at the ESO Very Large Telescope are also presented here. These images clearly reveal the resolved stellar population of HIZSS 3 for the first time. Narrowband Paβ images of the H II region are used in combination with previously published Hα data to obtain an independent line-of-sight extinction estimate: E(B - V) = 1.32 ± 0.04. The adopted foreground extinction is E(B - V) = 1.36 ± 0.06. Using the K-band luminosity function and K, J - K color-magnitude diagram, the apparent magnitude and color of the tip of the red giant branch are derived. In turn, these parameters are combined with the adopted foreground extinction to estimate the distance (1.69 ± 0.07 Mpc) and mean red giant branch metallicity ([Fe/H] = -0.5 ± 0.1). As an ensemble, these new observations significantly strengthen the conclusion that HIZSS 3 is a newly discovered low-mass dIrr galaxy lurking behind the Milky Way in the outskirts of the Local Group.

Original languageEnglish (US)
Pages (from-to)148-158
Number of pages11
JournalAstrophysical Journal
Volume623
Issue number1 I
DOIs
StatePublished - Apr 10 2005

Fingerprint

irregular galaxies
metallicity
extinction
H II regions
dwarf galaxies
line of sight
avoidance
color-magnitude diagram
estimates
extremely high frequencies
European Southern Observatory
narrowband
observatories
observatory
diagram
luminosity
telescopes
radio
color
gases

Keywords

  • Galaxies: dwarf
  • Galaxies: individual (HIZSS 3)
  • Galaxies: irregular

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

The distance and metallicity of the newly discovered, nearby irregular galaxy HIZSS 3. / Silva, David R.; Massey, Philip; Eastwood, Kathleen D; Henning, P. A.

In: Astrophysical Journal, Vol. 623, No. 1 I, 10.04.2005, p. 148-158.

Research output: Contribution to journalArticle

Silva, David R. ; Massey, Philip ; Eastwood, Kathleen D ; Henning, P. A. / The distance and metallicity of the newly discovered, nearby irregular galaxy HIZSS 3. In: Astrophysical Journal. 2005 ; Vol. 623, No. 1 I. pp. 148-158.
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T1 - The distance and metallicity of the newly discovered, nearby irregular galaxy HIZSS 3

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N2 - HIZSS 3 is an H I source in the Zone of Avoidance. Its radio characteristics are consistent with it being a previously unknown, nearby (∼1.8 Mpc), low-mass dwarf irregular (dIrr) galaxy. Optical observations have shown that it contains a modest H n region, but they failed to reveal a resolved stellar population. New spectroscopic observations of the H n region obtained at the MMT Observatory are presented here. They are used to derive the line-of-sight extinction [E(B - V) = 1.41 ± 0.04] and gas metallicity (log O/H + 12 ∼ 7.8) of the H II region. New near-IR imaging observations obtained at the ESO Very Large Telescope are also presented here. These images clearly reveal the resolved stellar population of HIZSS 3 for the first time. Narrowband Paβ images of the H II region are used in combination with previously published Hα data to obtain an independent line-of-sight extinction estimate: E(B - V) = 1.32 ± 0.04. The adopted foreground extinction is E(B - V) = 1.36 ± 0.06. Using the K-band luminosity function and K, J - K color-magnitude diagram, the apparent magnitude and color of the tip of the red giant branch are derived. In turn, these parameters are combined with the adopted foreground extinction to estimate the distance (1.69 ± 0.07 Mpc) and mean red giant branch metallicity ([Fe/H] = -0.5 ± 0.1). As an ensemble, these new observations significantly strengthen the conclusion that HIZSS 3 is a newly discovered low-mass dIrr galaxy lurking behind the Milky Way in the outskirts of the Local Group.

AB - HIZSS 3 is an H I source in the Zone of Avoidance. Its radio characteristics are consistent with it being a previously unknown, nearby (∼1.8 Mpc), low-mass dwarf irregular (dIrr) galaxy. Optical observations have shown that it contains a modest H n region, but they failed to reveal a resolved stellar population. New spectroscopic observations of the H n region obtained at the MMT Observatory are presented here. They are used to derive the line-of-sight extinction [E(B - V) = 1.41 ± 0.04] and gas metallicity (log O/H + 12 ∼ 7.8) of the H II region. New near-IR imaging observations obtained at the ESO Very Large Telescope are also presented here. These images clearly reveal the resolved stellar population of HIZSS 3 for the first time. Narrowband Paβ images of the H II region are used in combination with previously published Hα data to obtain an independent line-of-sight extinction estimate: E(B - V) = 1.32 ± 0.04. The adopted foreground extinction is E(B - V) = 1.36 ± 0.06. Using the K-band luminosity function and K, J - K color-magnitude diagram, the apparent magnitude and color of the tip of the red giant branch are derived. In turn, these parameters are combined with the adopted foreground extinction to estimate the distance (1.69 ± 0.07 Mpc) and mean red giant branch metallicity ([Fe/H] = -0.5 ± 0.1). As an ensemble, these new observations significantly strengthen the conclusion that HIZSS 3 is a newly discovered low-mass dIrr galaxy lurking behind the Milky Way in the outskirts of the Local Group.

KW - Galaxies: dwarf

KW - Galaxies: individual (HIZSS 3)

KW - Galaxies: irregular

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