Transformation of a virgo cluster dwarf irregular galaxy by ram pressure stripping: IC3418 and its fireballs

Jeffrey D.P. Kenney, Marla Geha, Pavel Jáchym, Hugh H. Crowl, William Dague, Aeree Chung, Jacqueline Van Gorkom, Bernd Vollmer

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We present optical imaging and spectroscopy and H I imaging of the Virgo Cluster galaxy IC 3418, which is likely a "smoking gun" example of the transformation of a dwarf irregular into a dwarf elliptical galaxy by ram pressure stripping. IC 3418 has a spectacular 17 kpc length UV-bright tail comprised of knots, head-tail, and linear stellar features. The only Hα emission arises from a few H II regions in the tail, the brightest of which are at the heads of head-tail UV sources whose tails point toward the galaxy ("fireballs"). Several of the elongated tail sources have Hα peaks outwardly offset by 80-150 pc from the UV peaks, suggesting that gas clumps continue to accelerate through ram pressure, leaving behind streams of newly formed stars which have decoupled from the gas. Absorption line strengths, measured from Keck DEIMOS spectra, together with UV colors, show star formation stopped 300 ± 100 Myr ago in the main body, and a strong starburst occurred prior to quenching. While neither Hα nor H I emission are detected in the main body of the galaxy, we have detected 4 × 10 7 M of H I from the tail with the Very Large Array. The velocities of tail H II regions, measured from Keck LRIS spectra, extend only a small fraction of the way to the cluster velocity, suggesting that star formation does not happen in more distant parts of the tail. Stars in the outer tail have velocities exceeding the escape speed, but some in the inner tail should fall back into the galaxy, forming halo streams.

Original languageEnglish
Article number119 (20pp)
JournalAstrophysical Journal
Volume780
Issue number2
DOIs
Publication statusPublished - 2014 Jan 10

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irregular galaxies
ram
fireballs
dwarf galaxies
stripping
galaxies
H II regions
star formation
gas
stars
Very Large Array (VLA)
elliptical galaxies
clumps
spectroscopy
gases
escape
halos
quenching
color

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kenney, Jeffrey D.P. ; Geha, Marla ; Jáchym, Pavel ; Crowl, Hugh H. ; Dague, William ; Chung, Aeree ; Van Gorkom, Jacqueline ; Vollmer, Bernd. / Transformation of a virgo cluster dwarf irregular galaxy by ram pressure stripping : IC3418 and its fireballs. In: Astrophysical Journal. 2014 ; Vol. 780, No. 2.
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Kenney, JDP, Geha, M, Jáchym, P, Crowl, HH, Dague, W, Chung, A, Van Gorkom, J & Vollmer, B 2014, 'Transformation of a virgo cluster dwarf irregular galaxy by ram pressure stripping: IC3418 and its fireballs', Astrophysical Journal, vol. 780, no. 2, 119 (20pp). https://doi.org/10.1088/0004-637X/780/2/119

Transformation of a virgo cluster dwarf irregular galaxy by ram pressure stripping : IC3418 and its fireballs. / Kenney, Jeffrey D.P.; Geha, Marla; Jáchym, Pavel; Crowl, Hugh H.; Dague, William; Chung, Aeree; Van Gorkom, Jacqueline; Vollmer, Bernd.

In: Astrophysical Journal, Vol. 780, No. 2, 119 (20pp), 10.01.2014.

Research output: Contribution to journalArticle

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AU - Kenney, Jeffrey D.P.

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AU - Crowl, Hugh H.

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AU - Van Gorkom, Jacqueline

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N2 - We present optical imaging and spectroscopy and H I imaging of the Virgo Cluster galaxy IC 3418, which is likely a "smoking gun" example of the transformation of a dwarf irregular into a dwarf elliptical galaxy by ram pressure stripping. IC 3418 has a spectacular 17 kpc length UV-bright tail comprised of knots, head-tail, and linear stellar features. The only Hα emission arises from a few H II regions in the tail, the brightest of which are at the heads of head-tail UV sources whose tails point toward the galaxy ("fireballs"). Several of the elongated tail sources have Hα peaks outwardly offset by 80-150 pc from the UV peaks, suggesting that gas clumps continue to accelerate through ram pressure, leaving behind streams of newly formed stars which have decoupled from the gas. Absorption line strengths, measured from Keck DEIMOS spectra, together with UV colors, show star formation stopped 300 ± 100 Myr ago in the main body, and a strong starburst occurred prior to quenching. While neither Hα nor H I emission are detected in the main body of the galaxy, we have detected 4 × 10 7 M of H I from the tail with the Very Large Array. The velocities of tail H II regions, measured from Keck LRIS spectra, extend only a small fraction of the way to the cluster velocity, suggesting that star formation does not happen in more distant parts of the tail. Stars in the outer tail have velocities exceeding the escape speed, but some in the inner tail should fall back into the galaxy, forming halo streams.

AB - We present optical imaging and spectroscopy and H I imaging of the Virgo Cluster galaxy IC 3418, which is likely a "smoking gun" example of the transformation of a dwarf irregular into a dwarf elliptical galaxy by ram pressure stripping. IC 3418 has a spectacular 17 kpc length UV-bright tail comprised of knots, head-tail, and linear stellar features. The only Hα emission arises from a few H II regions in the tail, the brightest of which are at the heads of head-tail UV sources whose tails point toward the galaxy ("fireballs"). Several of the elongated tail sources have Hα peaks outwardly offset by 80-150 pc from the UV peaks, suggesting that gas clumps continue to accelerate through ram pressure, leaving behind streams of newly formed stars which have decoupled from the gas. Absorption line strengths, measured from Keck DEIMOS spectra, together with UV colors, show star formation stopped 300 ± 100 Myr ago in the main body, and a strong starburst occurred prior to quenching. While neither Hα nor H I emission are detected in the main body of the galaxy, we have detected 4 × 10 7 M of H I from the tail with the Very Large Array. The velocities of tail H II regions, measured from Keck LRIS spectra, extend only a small fraction of the way to the cluster velocity, suggesting that star formation does not happen in more distant parts of the tail. Stars in the outer tail have velocities exceeding the escape speed, but some in the inner tail should fall back into the galaxy, forming halo streams.

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