Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy

Myung Goon Lee, Hong Soo Park, Jang Hyun Park, Young-Jong Sohn, Seung Joon Oh, In Soo Yuk, Soo Chang Rey, Sang Gak Lee, Young-Wook Lee, Ho Il Kim, Wonyong Han, Won Kee Park, Joon Hyeop Lee, Young Beom Jeon, Sang Chul Kim

Research output: Contribution to journalArticle

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Abstract

We present deep wide-field VI CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group, covering a field of 42′ × 28′ located at the center of the galaxy (supplemented by short B photometry). The limiting magnitudes with 50% completeness are V= 24.4 mag and I = 23.6 mag. Color-magnitude diagrams of the Sextans dSph show a well-defined red giant branch (RGB), blue horizontal branch (BHB), prominent red horizontal branch (RHB), and asymptotic giant branch (AGB), as well as ∼120 variable star candidates including RR Lyrae stars and anomalous Cepheids, ∼230 blue stragglers (BSs), and main-sequence (MS) stars. The main-sequence turnoff (MSTO) of the old population is found to be located at V ≈ 23.7 mag and V-I ≈ 0.56. The distance to the galaxy is derived using the I-band magnitude of the tip of the RGB at I TRGB = 15.95 ± 0.04: (m - M) 0 = 19.90 ± 0.06, for an adopted reddening of E(B- V) = 0.01. This estimate agrees well with the distance estimate based on the mean V-band magnitude of the HB at V(HB) = 20.37 ± 0.04. The mean metallicity of the RGB is estimated from the V-I color: [Fe/H] = -2.1 ± 0.1 (statistical error) ±0.2 (standard calibration error) dex, with a dispersion of σ[Fe/H] = 0.2 dex. The age of the MSTO of the main old population is estimated to be similar to that of the metal-poor Galactic globular cluster M92, and some stellar populations with younger age are seen. There is found to be one RGB bump at V = 19.95 ± 0.05 mag (M V= 0.03 mag) and a weak brighter bump at V= 19.35 ± 0.05 mag (M v= -0.58 mag), which is probably an AGB bump. The V-band luminosity function of the RGB and MS stars is in general similar to that of the globular cluster M92, with a slight excess of stars in the magnitude range brighter than the MSTO with respect to that of M92. The bright BSs are more centrally concentrated than the faint BSs. The V-band luminosity function of the BSs in the inner region is found to extend to a brighter magnitude and to have a flatter slope compared with that of the BSs in the outer region. Significant radial gradients are seen for several kinds of populations: the RHB, the red RGB, the red subgiant branch (SGB), and the bright BSs are more centrally concentrated toward the center of the galaxy compared with the BHB, the blue RGB, the blue SGB, and the faint BSs, respectively.

Original languageEnglish
Pages (from-to)2840-2866
Number of pages27
JournalAstronomical Journal
Volume126
Issue number6 1776
Publication statusPublished - 2003 Dec 1

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dwarf galaxies
photometry
charge coupled devices
extremely high frequencies
main sequence stars
galaxies
globular clusters
luminosity
stars
variable stars
color-magnitude diagram
completeness
estimates
metallicity
coverings
slopes
color
gradients
diagram
calibration

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Lee, M. G., Park, H. S., Park, J. H., Sohn, Y-J., Oh, S. J., Yuk, I. S., ... Kim, S. C. (2003). Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy. Astronomical Journal, 126(6 1776), 2840-2866.
Lee, Myung Goon ; Park, Hong Soo ; Park, Jang Hyun ; Sohn, Young-Jong ; Oh, Seung Joon ; Yuk, In Soo ; Rey, Soo Chang ; Lee, Sang Gak ; Lee, Young-Wook ; Kim, Ho Il ; Han, Wonyong ; Park, Won Kee ; Lee, Joon Hyeop ; Jeon, Young Beom ; Kim, Sang Chul. / Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy. In: Astronomical Journal. 2003 ; Vol. 126, No. 6 1776. pp. 2840-2866.
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abstract = "We present deep wide-field VI CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group, covering a field of 42′ × 28′ located at the center of the galaxy (supplemented by short B photometry). The limiting magnitudes with 50{\%} completeness are V= 24.4 mag and I = 23.6 mag. Color-magnitude diagrams of the Sextans dSph show a well-defined red giant branch (RGB), blue horizontal branch (BHB), prominent red horizontal branch (RHB), and asymptotic giant branch (AGB), as well as ∼120 variable star candidates including RR Lyrae stars and anomalous Cepheids, ∼230 blue stragglers (BSs), and main-sequence (MS) stars. The main-sequence turnoff (MSTO) of the old population is found to be located at V ≈ 23.7 mag and V-I ≈ 0.56. The distance to the galaxy is derived using the I-band magnitude of the tip of the RGB at I TRGB = 15.95 ± 0.04: (m - M) 0 = 19.90 ± 0.06, for an adopted reddening of E(B- V) = 0.01. This estimate agrees well with the distance estimate based on the mean V-band magnitude of the HB at V(HB) = 20.37 ± 0.04. The mean metallicity of the RGB is estimated from the V-I color: [Fe/H] = -2.1 ± 0.1 (statistical error) ±0.2 (standard calibration error) dex, with a dispersion of σ[Fe/H] = 0.2 dex. The age of the MSTO of the main old population is estimated to be similar to that of the metal-poor Galactic globular cluster M92, and some stellar populations with younger age are seen. There is found to be one RGB bump at V = 19.95 ± 0.05 mag (M V= 0.03 mag) and a weak brighter bump at V= 19.35 ± 0.05 mag (M v= -0.58 mag), which is probably an AGB bump. The V-band luminosity function of the RGB and MS stars is in general similar to that of the globular cluster M92, with a slight excess of stars in the magnitude range brighter than the MSTO with respect to that of M92. The bright BSs are more centrally concentrated than the faint BSs. The V-band luminosity function of the BSs in the inner region is found to extend to a brighter magnitude and to have a flatter slope compared with that of the BSs in the outer region. Significant radial gradients are seen for several kinds of populations: the RHB, the red RGB, the red subgiant branch (SGB), and the bright BSs are more centrally concentrated toward the center of the galaxy compared with the BHB, the blue RGB, the blue SGB, and the faint BSs, respectively.",
author = "Lee, {Myung Goon} and Park, {Hong Soo} and Park, {Jang Hyun} and Young-Jong Sohn and Oh, {Seung Joon} and Yuk, {In Soo} and Rey, {Soo Chang} and Lee, {Sang Gak} and Young-Wook Lee and Kim, {Ho Il} and Wonyong Han and Park, {Won Kee} and Lee, {Joon Hyeop} and Jeon, {Young Beom} and Kim, {Sang Chul}",
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Lee, MG, Park, HS, Park, JH, Sohn, Y-J, Oh, SJ, Yuk, IS, Rey, SC, Lee, SG, Lee, Y-W, Kim, HI, Han, W, Park, WK, Lee, JH, Jeon, YB & Kim, SC 2003, 'Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy', Astronomical Journal, vol. 126, no. 6 1776, pp. 2840-2866.

Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy. / Lee, Myung Goon; Park, Hong Soo; Park, Jang Hyun; Sohn, Young-Jong; Oh, Seung Joon; Yuk, In Soo; Rey, Soo Chang; Lee, Sang Gak; Lee, Young-Wook; Kim, Ho Il; Han, Wonyong; Park, Won Kee; Lee, Joon Hyeop; Jeon, Young Beom; Kim, Sang Chul.

In: Astronomical Journal, Vol. 126, No. 6 1776, 01.12.2003, p. 2840-2866.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy

AU - Lee, Myung Goon

AU - Park, Hong Soo

AU - Park, Jang Hyun

AU - Sohn, Young-Jong

AU - Oh, Seung Joon

AU - Yuk, In Soo

AU - Rey, Soo Chang

AU - Lee, Sang Gak

AU - Lee, Young-Wook

AU - Kim, Ho Il

AU - Han, Wonyong

AU - Park, Won Kee

AU - Lee, Joon Hyeop

AU - Jeon, Young Beom

AU - Kim, Sang Chul

PY - 2003/12/1

Y1 - 2003/12/1

N2 - We present deep wide-field VI CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group, covering a field of 42′ × 28′ located at the center of the galaxy (supplemented by short B photometry). The limiting magnitudes with 50% completeness are V= 24.4 mag and I = 23.6 mag. Color-magnitude diagrams of the Sextans dSph show a well-defined red giant branch (RGB), blue horizontal branch (BHB), prominent red horizontal branch (RHB), and asymptotic giant branch (AGB), as well as ∼120 variable star candidates including RR Lyrae stars and anomalous Cepheids, ∼230 blue stragglers (BSs), and main-sequence (MS) stars. The main-sequence turnoff (MSTO) of the old population is found to be located at V ≈ 23.7 mag and V-I ≈ 0.56. The distance to the galaxy is derived using the I-band magnitude of the tip of the RGB at I TRGB = 15.95 ± 0.04: (m - M) 0 = 19.90 ± 0.06, for an adopted reddening of E(B- V) = 0.01. This estimate agrees well with the distance estimate based on the mean V-band magnitude of the HB at V(HB) = 20.37 ± 0.04. The mean metallicity of the RGB is estimated from the V-I color: [Fe/H] = -2.1 ± 0.1 (statistical error) ±0.2 (standard calibration error) dex, with a dispersion of σ[Fe/H] = 0.2 dex. The age of the MSTO of the main old population is estimated to be similar to that of the metal-poor Galactic globular cluster M92, and some stellar populations with younger age are seen. There is found to be one RGB bump at V = 19.95 ± 0.05 mag (M V= 0.03 mag) and a weak brighter bump at V= 19.35 ± 0.05 mag (M v= -0.58 mag), which is probably an AGB bump. The V-band luminosity function of the RGB and MS stars is in general similar to that of the globular cluster M92, with a slight excess of stars in the magnitude range brighter than the MSTO with respect to that of M92. The bright BSs are more centrally concentrated than the faint BSs. The V-band luminosity function of the BSs in the inner region is found to extend to a brighter magnitude and to have a flatter slope compared with that of the BSs in the outer region. Significant radial gradients are seen for several kinds of populations: the RHB, the red RGB, the red subgiant branch (SGB), and the bright BSs are more centrally concentrated toward the center of the galaxy compared with the BHB, the blue RGB, the blue SGB, and the faint BSs, respectively.

AB - We present deep wide-field VI CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group, covering a field of 42′ × 28′ located at the center of the galaxy (supplemented by short B photometry). The limiting magnitudes with 50% completeness are V= 24.4 mag and I = 23.6 mag. Color-magnitude diagrams of the Sextans dSph show a well-defined red giant branch (RGB), blue horizontal branch (BHB), prominent red horizontal branch (RHB), and asymptotic giant branch (AGB), as well as ∼120 variable star candidates including RR Lyrae stars and anomalous Cepheids, ∼230 blue stragglers (BSs), and main-sequence (MS) stars. The main-sequence turnoff (MSTO) of the old population is found to be located at V ≈ 23.7 mag and V-I ≈ 0.56. The distance to the galaxy is derived using the I-band magnitude of the tip of the RGB at I TRGB = 15.95 ± 0.04: (m - M) 0 = 19.90 ± 0.06, for an adopted reddening of E(B- V) = 0.01. This estimate agrees well with the distance estimate based on the mean V-band magnitude of the HB at V(HB) = 20.37 ± 0.04. The mean metallicity of the RGB is estimated from the V-I color: [Fe/H] = -2.1 ± 0.1 (statistical error) ±0.2 (standard calibration error) dex, with a dispersion of σ[Fe/H] = 0.2 dex. The age of the MSTO of the main old population is estimated to be similar to that of the metal-poor Galactic globular cluster M92, and some stellar populations with younger age are seen. There is found to be one RGB bump at V = 19.95 ± 0.05 mag (M V= 0.03 mag) and a weak brighter bump at V= 19.35 ± 0.05 mag (M v= -0.58 mag), which is probably an AGB bump. The V-band luminosity function of the RGB and MS stars is in general similar to that of the globular cluster M92, with a slight excess of stars in the magnitude range brighter than the MSTO with respect to that of M92. The bright BSs are more centrally concentrated than the faint BSs. The V-band luminosity function of the BSs in the inner region is found to extend to a brighter magnitude and to have a flatter slope compared with that of the BSs in the outer region. Significant radial gradients are seen for several kinds of populations: the RHB, the red RGB, the red subgiant branch (SGB), and the bright BSs are more centrally concentrated toward the center of the galaxy compared with the BHB, the blue RGB, the blue SGB, and the faint BSs, respectively.

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Lee MG, Park HS, Park JH, Sohn Y-J, Oh SJ, Yuk IS et al. Deep wide-field BVI CCD photometry of the Sextans dwarf spheroidal galaxy. Astronomical Journal. 2003 Dec 1;126(6 1776):2840-2866.