Swift ultraviolet/Optical Telescope imaging of star-forming regions in M81 and Holmberg IX

E. A. Hoversten, C. Gronwall, D. E. Vanden Berk, A. R. Basu-Zych, A. A. Breeveld, P. J. Brown, N. P.M. Kuin, M. J. Page, P. W.A. Roming, M. H. Siegel

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928 Å ; uvm2: 2246 Å ; uvw1: 2600Å ) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies. In agreement with earlier studies, we find evidence for a burst in star formation in both galaxies starting ∼200Myr ago coincident with the suggested time of an M81-M82 interaction. In line with theories of its origin as a tidal dwarf, we find that the luminosity-weighted age of Holmberg IX is a few hundred million years. Both galaxies are best fit by a Milky Way dust extinction law with a prominent 2175 Å bump. In addition, we describe a stacked median filter technique for modeling the diffuse background light within a galaxy and a Markov chain method for cleaning segment maps generated by SExtractor.

Original languageEnglish (US)
Article number205
JournalAstronomical Journal
Volume141
Issue number6
DOIs
StatePublished - Jun 1 2011

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telescopes
galaxies
filter
stars
Markov chain
modeling
energy
pixel
extinction
spectral energy distribution
dust
ultraviolet filters
Markov chains
cleaning
photometry
method
distribution
star formation
bursts
brightness

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Hoversten, E. A. ; Gronwall, C. ; Vanden Berk, D. E. ; Basu-Zych, A. R. ; Breeveld, A. A. ; Brown, P. J. ; Kuin, N. P.M. ; Page, M. J. ; Roming, P. W.A. ; Siegel, M. H. / Swift ultraviolet/Optical Telescope imaging of star-forming regions in M81 and Holmberg IX. In: Astronomical Journal. 2011 ; Vol. 141, No. 6.
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abstract = "We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928 {\AA} ; uvm2: 2246 {\AA} ; uvw1: 2600{\AA} ) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies. In agreement with earlier studies, we find evidence for a burst in star formation in both galaxies starting ∼200Myr ago coincident with the suggested time of an M81-M82 interaction. In line with theories of its origin as a tidal dwarf, we find that the luminosity-weighted age of Holmberg IX is a few hundred million years. Both galaxies are best fit by a Milky Way dust extinction law with a prominent 2175 {\AA} bump. In addition, we describe a stacked median filter technique for modeling the diffuse background light within a galaxy and a Markov chain method for cleaning segment maps generated by SExtractor.",
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Hoversten, EA, Gronwall, C, Vanden Berk, DE, Basu-Zych, AR, Breeveld, AA, Brown, PJ, Kuin, NPM, Page, MJ, Roming, PWA & Siegel, MH 2011, 'Swift ultraviolet/Optical Telescope imaging of star-forming regions in M81 and Holmberg IX', Astronomical Journal, vol. 141, no. 6, 205. https://doi.org/10.1088/0004-6256/141/6/205

Swift ultraviolet/Optical Telescope imaging of star-forming regions in M81 and Holmberg IX. / Hoversten, E. A.; Gronwall, C.; Vanden Berk, D. E.; Basu-Zych, A. R.; Breeveld, A. A.; Brown, P. J.; Kuin, N. P.M.; Page, M. J.; Roming, P. W.A.; Siegel, M. H.

In: Astronomical Journal, Vol. 141, No. 6, 205, 01.06.2011.

Research output: Contribution to journalArticle

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AU - Hoversten, E. A.

AU - Gronwall, C.

AU - Vanden Berk, D. E.

AU - Basu-Zych, A. R.

AU - Breeveld, A. A.

AU - Brown, P. J.

AU - Kuin, N. P.M.

AU - Page, M. J.

AU - Roming, P. W.A.

AU - Siegel, M. H.

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N2 - We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928 Å ; uvm2: 2246 Å ; uvw1: 2600Å ) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies. In agreement with earlier studies, we find evidence for a burst in star formation in both galaxies starting ∼200Myr ago coincident with the suggested time of an M81-M82 interaction. In line with theories of its origin as a tidal dwarf, we find that the luminosity-weighted age of Holmberg IX is a few hundred million years. Both galaxies are best fit by a Milky Way dust extinction law with a prominent 2175 Å bump. In addition, we describe a stacked median filter technique for modeling the diffuse background light within a galaxy and a Markov chain method for cleaning segment maps generated by SExtractor.

AB - We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928 Å ; uvm2: 2246 Å ; uvw1: 2600Å ) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies. In agreement with earlier studies, we find evidence for a burst in star formation in both galaxies starting ∼200Myr ago coincident with the suggested time of an M81-M82 interaction. In line with theories of its origin as a tidal dwarf, we find that the luminosity-weighted age of Holmberg IX is a few hundred million years. Both galaxies are best fit by a Milky Way dust extinction law with a prominent 2175 Å bump. In addition, we describe a stacked median filter technique for modeling the diffuse background light within a galaxy and a Markov chain method for cleaning segment maps generated by SExtractor.

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