TY  - JOUR
A1  - Richter, Philipp
A1  - Fox, Andrew J.
A1  - Wakker, Bart P.
A1  - Howk, J. Christopher
A1  - Lehner, Nicolas
A1  - Barger, Kathleen A.
A1  - Lockman, Felix J.
T1  - New constraints on the nature and origin of the leading arm of the magellanic stream
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present a new precision measurement of gas-phase abundances of S, O, N, Si, Fe, P, Al, Ca as well as molecular hydrogen (H-2) in the Leading Arm (region II, LA II) of the Magellanic Stream (MS) toward the Seyfert galaxy NGC 3783. The results are based on high-quality archival ultraviolet/optical/radio data from various different instruments (HST/STIS, FUSE, AAT, GBT, GB140 ft, ATCA). Our study updates previous results from lower-resolution data and provides for the first time a self-consistent component model of the complex multiphase absorber, delivering important constraints on the nature and origin of LA II. We derive a uniform, moderate a abundance in the two main absorber groups at +245 and +190 km s(-1) of alpha/H = 0.30 +/- 0.05 solar, a low nitrogen abundance of N/H = 0.05 +/- 0.01 solar, and a high dust content with substantial dust depletion values for Si, Fe, Al, and Ca. These a, N, and dust abundances in LA II are similar to those observed in the Small Magellanic Cloud (SMC). From the analysis of the H2 absorption, we determine a high thermal pressure of P/k approximate to 1680 K cm(-3) in LA II, in line with the idea that LA II is located in the inner Milky Way halo at a z-height of < 20 kpc, where it hydrodynamically interacts with the ambient hot coronal gas. Our study supports a scenario in which LA II stems from the breakup of a metal- and dust-enriched progenitor cloud that was recently (200-500 Myr ago) stripped from the SMC.
KW  - Galaxy: evolution
KW  - Galaxy: halo
KW  - ISM: abundances
KW  - Magellanic Clouds
KW  - quasars: absorption lines
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aadd0f
SN  - 0004-637X
SN  - 1538-4357
VL  - 865
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Fox, Andrew J.
A1  - Barger, Kathleen A.
A1  - Wakker, Bart P.
A1  - Richter, Philipp
A1  - Antwi-Danso, Jacqueline
A1  - Casetti-Dinescu, Dana I.
A1  - Howk, J. Christopher
A1  - Lehner, Nicolas
A1  - Crowther, Paul A.
A1  - Lockman, Felix J.
T1  - Chemical Abundances in the Leading Arm of the Magellanic Stream
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The Leading Arm (LA) of the Magellanic Stream is a vast debris field of H I clouds connecting the Milky Way and the Magellanic Clouds. It represents an example of active gas accretion onto the Galaxy. Previously, only one chemical abundance measurement had been made in the LA. Here we present chemical abundance measurements using Hubble Space Telescope/Cosmic Origins Spectrograph and Green Bank Telescope spectra of four AGN sightlines passing through the LA and three nearby sightlines that may trace outer fragments of the LA. We find low oxygen abundances, ranging from 4.0+(2.0)(2.0)% 12.6(4.1)(6.0)% solar, in the confirmed LA directions, with the lowest values found in the region known as LA III, farthest from the LMC. These abundances are substantially lower than the single previous measurement, S/H = 35 +/- 7% solar, but are in agreement with those reported in the SMC filament of the trailing Stream, supporting a common origin in the SMC (not the LMC) for the majority of the LA and trailing Stream. This provides important constraints for models of the formation of the Magellanic System. Finally, two of the three nearby sightlines show high-velocity clouds with H I columns, kinematics, and oxygen abundances consistent with LA membership. This suggests that the LA is larger than traditionally thought, extending at least 20 degrees further to the Galactic northwest.
KW  - Galaxy: evolution
KW  - Galaxy: halo
KW  - ISM: abundances
KW  - Magellanic Clouds
KW  - quasars: absorption lines
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aaa9bb
SN  - 0004-637X
SN  - 1538-4357
VL  - 854
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -