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 ) towards 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 multi-phase absorber , delivering important constraints on the nature and origin of LA II .
We derive a uniform , moderate \alpha abundance in the two main absorber groups at +245 and +190 km s ^ { -1 } of \alpha /H = 0.30 \pm 0.05 solar , a low nitrogen abundance of N/H = 0.05 \pm 0.01 solar , and a high dust content with substantial dust depletion values for Si , Fe , Al , and Ca .
These \alpha , N , and dust abundances in LA II are similar to those observed in the Small Magellanic Cloud ( SMC ) .
From the analysis of the H _ { 2 } absorption , we determine a high thermal pressure of P / k \approx 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 break-up of a metal- and dust-enriched progenitor cloud that was recently ( 200 - 500 Myr ago ) stripped from the SMC .