Hα Distances to the Leading Arm of the Magellanic Stream

Antwi-Danso, Jacqueline; Barger, Kat; Haffner, L. M.

doi:10.3847/1538-4357/ab6ef9

Cited by 12 publications

(10 citation statements)

References 65 publications

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“…If in the strong cooling regime, which seems applicable, the present-day Leading Arm is likely a series of clumps in the long cooling tail behind the progenitor cloud. This is consistent with observations, which find a clear distance variation along the Leading Arm (Venzmer et al 2012;For et al 2016;Antwi-Danso et al 2020). The clumpy, fragmented nature of the Leading Arm, rather than a coherent tail, could be due to cut-offs in observational sensitivity, i.e.…”

Section: The Leading Arm: Analytic Estimatessupporting

confidence: 91%

Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris

Bustard,

Gronke

2021

Preprint

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The Magellanic Stream is sculpted by its infall through the Milky Way's circumgalactic medium, but the rates and directions of mass, momentum, and energy exchange through the Stream-halo interface are relative unknowns critical for determining the origin and fate of the Stream. Complementary to large-scale simulations of LMC-SMC interactions, we apply new insights derived from idealized, highresolution "cloud-crushing" and radiative turbulent mixing layer simulations to the Leading Arm and Trailing Stream. Contrary to classical expectations of fast cloud breakup, we predict that the Leading Arm and much of the Trailing Stream should be surviving infall and even gaining mass due to strong radiative cooling. Provided a sufficiently supersonic tidal swing-out from the Clouds, the present-day Leading Arm could be a series of high-density clumps in the cooling tail behind the progenitor cloud. We back up our analytic framework with a suite of converged wind-tunnel simulations, finding that previous results on cloud survival and mass growth can be extended to high Mach number (M) flows with a modified drag time t drag ∝ 1 + M and longer growth time. We also simulate the Trailing Stream; we find that the growth time is long (∼ Gyrs) compared to the infall time, and approximate Hα emission is low on average (∼few mR) but can be up to tens of mR in bright spots. Our findings also have broader extragalactic implications for e.g. galactic winds, which we discuss.

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Section: The Leading Arm: Analytic Estimatessupporting

confidence: 91%

Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris

Bustard,

Gronke

2021

Preprint

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“…In contrast, there is no evidence for photoionized Si IV and C IV in the Leading Arm, because its Si IV and C IV components tend to be broader and therefore collisionally ionized. The different ionization mechanism for the high ions can be understood in terms of the LA's proximity to the MW (d LA ≈20 kpc; McClure-Griffiths et al 2008;Antwi-Danso et al 2020), which causes it to interact with a much denser external medium than the Stream does (d MS ≈75-150 kpc according to models; Besla et al 2007;Pardy et al 2018;Lucchini et al 2020).…”

Section: Discussionmentioning

confidence: 99%

“…This proximity leads to an interaction with a much denser external medium than the Stream encounters. Both observations (McClure-Griffiths et al 2008;Antwi-Danso et al 2020) and models (Besla et al 2007;Pardy et al 2018) indicate that the Leading Arm (d LA ≈20 kpc) is much closer to the MW than the Stream is (d MS > 55 kpc, and possibly d MS ≈ 75 − 150 kpc). We suggest that distance (and therefore density of the external medium) is the primary reason why the high-ions appear to be collisionally ionized in the LA but not in the Stream.…”

Section: The Kinematics and Ionization Of The Leading Armmentioning

confidence: 96%

HST/COS data from Fox et al. 2020 ApJ Paper "Kinematics of the Magellanic Stream and Implications for its Ionization"

Fox

2020

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The Magellanic Stream and the Leading Arm form a massive, filamentary system of gas clouds surrounding the Large and Small Magellanic Clouds. Here we present a new component-level analysis of their ultraviolet (UV) kinematic properties using a sample of 31 sightlines through the Magellanic System observed with the Hubble Space Telescope/Cosmic Origins Spectrograph. Using Voigt profile fits to UV metal-line absorption, we quantify the kinematic differences between the low-ion (Si II and C II), intermediate-ion (Si III), and high-ion (Si IV and C IV) absorption lines and compare the kinematics between the Stream and Leading Arm. We find that the Stream shows generally simple, single-phase kinematics, with statistically indistinguishable b-value distributions for the low-, intermediate-, and high-ion components, all dominated by narrow (b 25 km s −1 ) components that are well aligned in velocity. In contrast, we find tentative evidence that the Leading Arm shows complex, multi-phase kinematics, with broader high ions than low ions. These results suggest that the Stream is photoionized up to C IV by a hard ionizing radiation field. This can be naturally explained by the Seyfert-flare model of Bland-Hawthorn et al. (2013, in which a burst of ionizing radiation from the Galactic Center photoionized the Stream as it passed below the south Galactic pole. The Seyfert flare is the only known source of radiation that is both powerful enough to explain the Hα intensity of the Stream and hard enough to photoionize Si IV and C IV to the observed levels. The flare's timescale of a few Myr suggests it is the same event that created the giant X-ray/γ-ray Fermi Bubbles at the Galactic Center.

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“…Therefore, we were unable to use either of these lines to calibrate our velocities using the method described in Hausen et al (2002) and . Instead, we used the velocity calibration technique that is described by Barger et al (2017) and Antwi-Danso et al (2020) for WHAM observations that do not overlap with bright atmospheric lines at well established transitions. Using this technique, we calibrated our velocity by monitoring the pressure of the SF 6 gas in the WHAM Fabry-Pérot etalons and by further refining the calibration by comparing our observations with an atmospheric template.…”

Section: Velocity Calibrationmentioning

confidence: 99%

“…Instead, we modeled the H i emission the LMC and its surroundings to convert our Hα observations into a LMCSR velocity reference frame. This is especially beneficial because the gaseous H i emission extends much further than the stellar disk and because Hα emission tends to kinematically follow the H i emission in HVCs (e.g., Haffner et al 2001;Putman et al 2003;Hill et al 2009;Barger et al 2012Barger et al , 2017Antwi-Danso et al 2020).…”

Section: Lmcsr Velocity Framementioning

confidence: 99%

Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in H$α$ Emission I

Ciampa,

Barger,

Lehner

et al. 2021

Preprint

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We present the first spectroscopically resolved Hα emission map of the Large Magellanic Cloud's (LMC) galactic wind. By combining new Wisconsin H-alpha Mapper (WHAM) observations (I Hα 10 mR) with existing H i 21-cm emission observations, we have (1) mapped the LMC's near-side galactic wind over a local standard of rest (LSR) velocity range of +50 ≤ v LSR ≤ +250 km s −1 , (2) determined its morphology and extent, and (3) estimated its mass, outflow rate, and mass-loading factor. We observe Hα emission from this wind to typically 1-degree off the LMC's H i disk. Kinematically, we find that the diffuse gas in the warm-ionized phase of this wind persists at both low ( 100 km s −1 ) and high ( 100 km s −1 ) velocities, relative to the LMC's H i disk. Furthermore, we find that the high-velocity component spatially aligns with the most intense star-forming region, 30 Doradus. We, therefore, conclude that this high-velocity material traces an active outflow. We estimate the mass of the warm (T e ≈ 10 4 K) ionized phase of the near-side LMC outflow to be log (M ionized /M ) = 7.51 ± 0.15 for the combined low and high velocity components. Assuming an ionization fraction of 75% and that the wind is symmetrical about the LMC disk, we estimate that its total (neutral and ionized) mass is log (M total /M ) = 7.93, its mass-flow rate is Ṁoutflow ≈ 1.43 M yr −1 , and its mass-loading factor is η ≈ 4.54. Our average mass-loading factor results are roughly a factor of 2.5 larger than previous Hα imaging and UV absorption line studies, suggesting that those studies are missing nearly half the gas in the outflows.

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Hα Distances to the Leading Arm of the Magellanic Stream

Cited by 12 publications

References 65 publications

Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris

Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris

HST/COS data from Fox et al. 2020 ApJ Paper "Kinematics of the Magellanic Stream and Implications for its Ionization"

Mapping the Supernovae Driven Winds of the Large Magellanic Cloud in H$α$ Emission I

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