Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations

Soo Chang Rey, Sangmo T. Sohn, Michael A. Beasley, Young Wook Lee, R. Michael Rich, Suk Jin Yoon, Sukyoung K. Yi, Luciana Bianch, Yongbeom Kang, Kyeongsook Lee, Chul Chung, Sang Yoon Lee, Tom A. Barlow, Karl Foster, Peter G. Friedman, D. Christopher Martin, Patrick Morrissey, Susan G. Neff, David Schiminovich, Mark SeibertTed K. Wyder, Jose Donas, Timothy M. Heckman, Barry F. Madore, Bruno Milliard, Alex S. Szalay, Barry Y. Welsh

Research output: Contribution to journalArticle

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Abstract

We explore the age distribution of the globular cluster (GC) system of the nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from GALEX observations, with UV-optical colors used as the age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and the Milky Way in the UV-optical color- color diagram, which indicates that the majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31 and the Milky Way. A large fraction of spectroscopically identified intermediate-age GC (IAGC) candidates with ∼3-8 Gyr are not detected in the far-UV (FUV) passband. Considering the nature of intermediate-age populations being faint in the FUV passband, we suggest that many of the spectroscopically identified IAGCs may be truly intermediate in age. This is in contrast to the case of M31 where a large fraction of spectroscopically suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but rather older GCs with developed blue horizontal branch stars. Our UV photometry strengthens the results previously suggesting the presence of GC and stellar subpopulation with intermediate age in NGC 5128. The existence of IAGCs strongly indicates the occurrence of at least one more major star formation episode after a starburst at high redshift.

Original languageEnglish
Pages (from-to)L11-L15
JournalAstrophysical Journal
Volume700
Issue number1 PART 2
DOIs
Publication statusPublished - 2009 Jan 1

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ultraviolet photometry
globular clusters
color-color diagram
horizontal branch stars
blue stars
elliptical galaxies
star formation
occurrences
trends
color
subpopulation
age structure
diagram

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Rey, Soo Chang ; Sohn, Sangmo T. ; Beasley, Michael A. ; Lee, Young Wook ; Rich, R. Michael ; Yoon, Suk Jin ; Yi, Sukyoung K. ; Bianch, Luciana ; Kang, Yongbeom ; Lee, Kyeongsook ; Chung, Chul ; Lee, Sang Yoon ; Barlow, Tom A. ; Foster, Karl ; Friedman, Peter G. ; Martin, D. Christopher ; Morrissey, Patrick ; Neff, Susan G. ; Schiminovich, David ; Seibert, Mark ; Wyder, Ted K. ; Donas, Jose ; Heckman, Timothy M. ; Madore, Barry F. ; Milliard, Bruno ; Szalay, Alex S. ; Welsh, Barry Y. / Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations. In: Astrophysical Journal. 2009 ; Vol. 700, No. 1 PART 2. pp. L11-L15.
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title = "Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations",
abstract = "We explore the age distribution of the globular cluster (GC) system of the nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from GALEX observations, with UV-optical colors used as the age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and the Milky Way in the UV-optical color- color diagram, which indicates that the majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31 and the Milky Way. A large fraction of spectroscopically identified intermediate-age GC (IAGC) candidates with ∼3-8 Gyr are not detected in the far-UV (FUV) passband. Considering the nature of intermediate-age populations being faint in the FUV passband, we suggest that many of the spectroscopically identified IAGCs may be truly intermediate in age. This is in contrast to the case of M31 where a large fraction of spectroscopically suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but rather older GCs with developed blue horizontal branch stars. Our UV photometry strengthens the results previously suggesting the presence of GC and stellar subpopulation with intermediate age in NGC 5128. The existence of IAGCs strongly indicates the occurrence of at least one more major star formation episode after a starburst at high redshift.",
author = "Rey, {Soo Chang} and Sohn, {Sangmo T.} and Beasley, {Michael A.} and Lee, {Young Wook} and Rich, {R. Michael} and Yoon, {Suk Jin} and Yi, {Sukyoung K.} and Luciana Bianch and Yongbeom Kang and Kyeongsook Lee and Chul Chung and Lee, {Sang Yoon} and Barlow, {Tom A.} and Karl Foster and Friedman, {Peter G.} and Martin, {D. Christopher} and Patrick Morrissey and Neff, {Susan G.} and David Schiminovich and Mark Seibert and Wyder, {Ted K.} and Jose Donas and Heckman, {Timothy M.} and Madore, {Barry F.} and Bruno Milliard and Szalay, {Alex S.} and Welsh, {Barry Y.}",
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Rey, SC, Sohn, ST, Beasley, MA, Lee, YW, Rich, RM, Yoon, SJ, Yi, SK, Bianch, L, Kang, Y, Lee, K, Chung, C, Lee, SY, Barlow, TA, Foster, K, Friedman, PG, Martin, DC, Morrissey, P, Neff, SG, Schiminovich, D, Seibert, M, Wyder, TK, Donas, J, Heckman, TM, Madore, BF, Milliard, B, Szalay, AS & Welsh, BY 2009, 'Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations', Astrophysical Journal, vol. 700, no. 1 PART 2, pp. L11-L15. https://doi.org/10.1088/0004-637X/700/1/L11

Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations. / Rey, Soo Chang; Sohn, Sangmo T.; Beasley, Michael A.; Lee, Young Wook; Rich, R. Michael; Yoon, Suk Jin; Yi, Sukyoung K.; Bianch, Luciana; Kang, Yongbeom; Lee, Kyeongsook; Chung, Chul; Lee, Sang Yoon; Barlow, Tom A.; Foster, Karl; Friedman, Peter G.; Martin, D. Christopher; Morrissey, Patrick; Neff, Susan G.; Schiminovich, David; Seibert, Mark; Wyder, Ted K.; Donas, Jose; Heckman, Timothy M.; Madore, Barry F.; Milliard, Bruno; Szalay, Alex S.; Welsh, Barry Y.

In: Astrophysical Journal, Vol. 700, No. 1 PART 2, 01.01.2009, p. L11-L15.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Probing the intermediate-age globular clusters in NGC 5128 from ultraviolet observations

AU - Rey, Soo Chang

AU - Sohn, Sangmo T.

AU - Beasley, Michael A.

AU - Lee, Young Wook

AU - Rich, R. Michael

AU - Yoon, Suk Jin

AU - Yi, Sukyoung K.

AU - Bianch, Luciana

AU - Kang, Yongbeom

AU - Lee, Kyeongsook

AU - Chung, Chul

AU - Lee, Sang Yoon

AU - Barlow, Tom A.

AU - Foster, Karl

AU - Friedman, Peter G.

AU - Martin, D. Christopher

AU - Morrissey, Patrick

AU - Neff, Susan G.

AU - Schiminovich, David

AU - Seibert, Mark

AU - Wyder, Ted K.

AU - Donas, Jose

AU - Heckman, Timothy M.

AU - Madore, Barry F.

AU - Milliard, Bruno

AU - Szalay, Alex S.

AU - Welsh, Barry Y.

PY - 2009/1/1

Y1 - 2009/1/1

N2 - We explore the age distribution of the globular cluster (GC) system of the nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from GALEX observations, with UV-optical colors used as the age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and the Milky Way in the UV-optical color- color diagram, which indicates that the majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31 and the Milky Way. A large fraction of spectroscopically identified intermediate-age GC (IAGC) candidates with ∼3-8 Gyr are not detected in the far-UV (FUV) passband. Considering the nature of intermediate-age populations being faint in the FUV passband, we suggest that many of the spectroscopically identified IAGCs may be truly intermediate in age. This is in contrast to the case of M31 where a large fraction of spectroscopically suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but rather older GCs with developed blue horizontal branch stars. Our UV photometry strengthens the results previously suggesting the presence of GC and stellar subpopulation with intermediate age in NGC 5128. The existence of IAGCs strongly indicates the occurrence of at least one more major star formation episode after a starburst at high redshift.

AB - We explore the age distribution of the globular cluster (GC) system of the nearby elliptical galaxy NGC 5128 using ultraviolet (UV) photometry from GALEX observations, with UV-optical colors used as the age indicator. Most GCs in NGC 5128 follow the general trends of GCs in M31 and the Milky Way in the UV-optical color- color diagram, which indicates that the majority of GCs in NGC 5128 are old similar to the age range of old GCs in M31 and the Milky Way. A large fraction of spectroscopically identified intermediate-age GC (IAGC) candidates with ∼3-8 Gyr are not detected in the far-UV (FUV) passband. Considering the nature of intermediate-age populations being faint in the FUV passband, we suggest that many of the spectroscopically identified IAGCs may be truly intermediate in age. This is in contrast to the case of M31 where a large fraction of spectroscopically suggested IAGCs are detected in FUV and therefore may not be genuine IAGCs but rather older GCs with developed blue horizontal branch stars. Our UV photometry strengthens the results previously suggesting the presence of GC and stellar subpopulation with intermediate age in NGC 5128. The existence of IAGCs strongly indicates the occurrence of at least one more major star formation episode after a starburst at high redshift.

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