The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way

Andrew J. Fox, Bart P. Wakker, Kathleen A. Barger, Audra K. Hernandez, Philipp Richter, Nicolas Lehner, Joss Bland-Hawthorn, Jane Camilla Charlton, Tobias Westmeier, Christopher Thom, Jason Tumlinson, Toru Misawa, J. Christopher Howk, L. Matthew Haffner, Justin Ely, Paola Rodriguez-Hidalgo, Nimisha Kumari

Research output: Contribution to journalReview article

61 Citations (Scopus)

Abstract

Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg2, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 109 M (d/55 kpc)2, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of ∼0.5-1.0 Gyr, it will represent an average inflow rate of ∼3.7-6.7 M yr-1, potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.

Original languageEnglish (US)
Article number147
JournalAstrophysical Journal
Volume787
Issue number2
DOIs
StatePublished - Jun 1 2014

Fingerprint

inflow
ionization
gases
gas
Magellanic clouds
coronas
gas ionization
corona
atomic weights
monatomic gases
ionized gases
star formation rate
Hubble Space Telescope
spectrographs
sky
rate
photoionization
halos
interactions
cross sections

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Fox, A. J., Wakker, B. P., Barger, K. A., Hernandez, A. K., Richter, P., Lehner, N., ... Kumari, N. (2014). The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way. Astrophysical Journal, 787(2), [147]. https://doi.org/10.1088/0004-637X/787/2/147
Fox, Andrew J. ; Wakker, Bart P. ; Barger, Kathleen A. ; Hernandez, Audra K. ; Richter, Philipp ; Lehner, Nicolas ; Bland-Hawthorn, Joss ; Charlton, Jane Camilla ; Westmeier, Tobias ; Thom, Christopher ; Tumlinson, Jason ; Misawa, Toru ; Howk, J. Christopher ; Haffner, L. Matthew ; Ely, Justin ; Rodriguez-Hidalgo, Paola ; Kumari, Nimisha. / The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way. In: Astrophysical Journal. 2014 ; Vol. 787, No. 2.
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abstract = "Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81{\%} (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg2, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 109 M ⊙ (d/55 kpc)2, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of ∼0.5-1.0 Gyr, it will represent an average inflow rate of ∼3.7-6.7 M ⊙ yr-1, potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.",
author = "Fox, {Andrew J.} and Wakker, {Bart P.} and Barger, {Kathleen A.} and Hernandez, {Audra K.} and Philipp Richter and Nicolas Lehner and Joss Bland-Hawthorn and Charlton, {Jane Camilla} and Tobias Westmeier and Christopher Thom and Jason Tumlinson and Toru Misawa and Howk, {J. Christopher} and Haffner, {L. Matthew} and Justin Ely and Paola Rodriguez-Hidalgo and Nimisha Kumari",
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Fox, AJ, Wakker, BP, Barger, KA, Hernandez, AK, Richter, P, Lehner, N, Bland-Hawthorn, J, Charlton, JC, Westmeier, T, Thom, C, Tumlinson, J, Misawa, T, Howk, JC, Haffner, LM, Ely, J, Rodriguez-Hidalgo, P & Kumari, N 2014, 'The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way', Astrophysical Journal, vol. 787, no. 2, 147. https://doi.org/10.1088/0004-637X/787/2/147

The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way. / Fox, Andrew J.; Wakker, Bart P.; Barger, Kathleen A.; Hernandez, Audra K.; Richter, Philipp; Lehner, Nicolas; Bland-Hawthorn, Joss; Charlton, Jane Camilla; Westmeier, Tobias; Thom, Christopher; Tumlinson, Jason; Misawa, Toru; Howk, J. Christopher; Haffner, L. Matthew; Ely, Justin; Rodriguez-Hidalgo, Paola; Kumari, Nimisha.

In: Astrophysical Journal, Vol. 787, No. 2, 147, 01.06.2014.

Research output: Contribution to journalReview article

TY - JOUR

T1 - The COS/UVES absorption survey of the Magellanic stream. III. ionization, total mass, and inflow rate onto the Milky Way

AU - Fox, Andrew J.

AU - Wakker, Bart P.

AU - Barger, Kathleen A.

AU - Hernandez, Audra K.

AU - Richter, Philipp

AU - Lehner, Nicolas

AU - Bland-Hawthorn, Joss

AU - Charlton, Jane Camilla

AU - Westmeier, Tobias

AU - Thom, Christopher

AU - Tumlinson, Jason

AU - Misawa, Toru

AU - Howk, J. Christopher

AU - Haffner, L. Matthew

AU - Ely, Justin

AU - Rodriguez-Hidalgo, Paola

AU - Kumari, Nimisha

PY - 2014/6/1

Y1 - 2014/6/1

N2 - Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg2, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 109 M ⊙ (d/55 kpc)2, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of ∼0.5-1.0 Gyr, it will represent an average inflow rate of ∼3.7-6.7 M ⊙ yr-1, potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.

AB - Dynamic interactions between the two Magellanic Clouds have flung large quantities of gas into the halo of the Milky Way. The result is a spectacular arrangement of gaseous structures, including the Magellanic Stream, the Magellanic Bridge, and the Leading Arm (collectively referred to as the Magellanic System). In this third paper of a series studying the Magellanic gas in absorption, we analyze the gas ionization level using a sample of 69 Hubble Space Telescope/Cosmic Origins Spectrograph sightlines that pass through or within 30° of the 21 cm emitting regions. We find that 81% (56/69) of the sightlines show UV absorption at Magellanic velocities, indicating that the total cross-section of the Magellanic System is ≈11,000 deg2, or around one-quarter of the entire sky. Using observations of the Si III/Si II ratio together with Cloudy photoionization modeling, we calculate the total gas mass (atomic plus ionized) of the Magellanic System to be ≈2.0 × 109 M ⊙ (d/55 kpc)2, with the ionized gas contributing around three times as much mass as the atomic gas. This is larger than the current-day interstellar H I mass of both Magellanic Clouds combined, indicating that they have lost most of their initial gas mass. If the gas in the Magellanic System survives to reach the Galactic disk over its inflow time of ∼0.5-1.0 Gyr, it will represent an average inflow rate of ∼3.7-6.7 M ⊙ yr-1, potentially raising the Galactic star formation rate. However, multiple signs of an evaporative interaction with the hot Galactic corona indicate that the Magellanic gas may not survive its journey to the disk fully intact and will instead add material to (and cool) the corona.

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