The Parkes H I Survey of the Magellanic System

Abstract

Abstract. We present the first fully and uniformly sampled, spatially complete H  survey of the entire Magellanic System with high velocity resolution (∆v = 1.0 km s −1 ), performed with the Parkes Telescope . Approximately 24 percent of the southern sky was covered by this survey on a ≈5 grid with an angular resolution of HPBW = 14. 1. A fully automated data-reduction scheme was developed for this survey to handle the large number of H  spectra (1.5 × 10 6 ). The individual Hanning smoothed and polarization averaged spectra have an rms brightness temperature noise of σ = 0.12 K. The final data-cubes have an rms noise of σ rms ≈ 0.05 K and an effective angular resolution of ≈16 . In this paper we describe the survey parameters, the datareduction and the general distribution of the H  gas. , if all H  gas is at the same distance of 55 kpc. Approximately two thirds of this H  gas is located close to the Magellanic Clouds (Magellanic Bridge and Interface Region), and 25% of the H  gas is associated with the Magellanic Stream. The Leading Arm has a four times lower H  mass than the Magellanic Stream, corresponding to 6% of the total H  mass of the gaseous features.We have analyzed the velocity field of the Magellanic Clouds and their neighborhood introducing a LMC-standard-of-rest frame. The H  in the Magellanic Bridge shows low velocities relative to the Magellanic Clouds suggesting an almost parallel motion, while the gas in the Interface Region has significantly higher relative velocities indicating that this gas is leaving the Magellanic Bridge building up a new section of the Magellanic Stream. The Leading Arm is connected to the Magellanic Bridge close to an extended arm of the LMC. The clouds in the Magellanic Stream and the Leading Arm show significant differences, both in the column density distribution and in the shapes of the line profiles. The H  gas in the Magellanic Stream is more smoothly distributed than the gas in the Leading Arm. These morphological differences can be explained if the Leading Arm is at considerably lower z-heights and embedded in a higher pressure ambient medium.

Under pressure: quenching star formation in low-mass satellite galaxies via stripping

“…However, the total HI gas mass attributed to the Magellanic Stream and Leading Arm versus that of the two Magellanic Clouds jointly is consistent with an average stripped fraction for the two systems of 25%, consistent with our expectations at M > 10 8 M (see Fig. 6, Brüns et al 2005;Nidever, Majewski & Butler Burton 2008;Nidever et al 2010).…”

Neutral Gas Accretion onto Nearby Galaxies

“…A distance of 55 kpc is assumed for both objects, though this has a large uncertainty; for a recent review see D 'Onghia & Fox (2016). The relevant H I masses are 3 × 10 8 M , and 3 × 10 7 M , for the Stream and Leading Arm, respectively (Brüns et al, 2005). The total mass of the Stream is ∼ 10 9 M , and is dominated by ionized gas (Fox et al, 2014).…”

“…If the HVCs are even in approximate pressure equilibrium with a galaxy's CGM they must be orders of magnitude more dense than the hot gas around them and thus falling toward the disk. There is some evidence for the interaction of Galactic HVCs with the CGM in the form of distortions of the cloud shapes (Brüns et al, 2000), and there is rather spectacular evidence for the direct accretion of H I onto the Milky Way from one HVC: The Smith Cloud.…”

The evolution of superluminous supernova LSQ14mo and its interacting host galaxy system

“…Fig. 3 of Brüns et al 2005). Hence, these three components may be kinematically associated, although it is not possible to distinguish whether the three components are part of a single galaxy with B and C being tidal tails of A, or if C is a satellite galaxy of A.…”