Extinction towards the cluster R136 in the Large Magellanic Cloud

The properties of ultraviolet interstellar extinction in and near the core of the 30 Doradus Nebula are studied. The pair method is employed using nine reddened stars from within 5′ (80pc) of the core and nine unreddened stars from a variety of locations in the large Magellanic Cloud. All of the 30 Doradus stars examined appear to be reddened by E(B-V) ⋍ 0.12 with an extinction law similar in wavelength dependence to those derived for the LMC by Koornneef and Code (1981) and Nandy et al. (1981). Several of the stars, including R136a, R145 and R147, are found to be additionally reddened by E(B-V) ⋍ 0.18 with an extinction law qualitatively similar in wavelength dependence to the law found in the Orion region. A two-component model, featuring a layer of “LMC foreground dust” which affects all of the stars and a deeper layer of “nebular dust” which affects some of the stars, provides the simplest explanation of the extinction properties. The 2200 Å extinction bump is present in both curves. The wavelength positions of the bump and the bump profiles, when normalized to a linear “background extinction”, are indistinguishable from the average Galactic bump. The strengths of the bumps, relative to E(B-V), are 20–30% weaker than for the Milky Way Curve.

view Abstract Citations (90) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar dust in the Large Magellanic Cloud. Clayton, G. C. ; Martin, P. G. Abstract This paper presents extensive observations of the properties of interstellar dust in the Large Magellanic Cloud. Extinction and polarization analysis of 12 reddened stars spread across the LMC shows that in the optical and infrared the dust characteristics are remarkably similar to the Galaxy. The wavelength dependence of the polarization and the polarization efficiency, p/E(B-V), are also comparable to galactic values. On average, the ultraviolet extinction in the LMC is also different from that in the Galaxy, having proportionately higher far-ultraviolet extinction and a weaker 2200 Å bump. The dust-to-gas ratio, E(B-V)/NH in the LMC is several times lower than the galactic value. A relationship between ultraviolet extinction properties and heavy element abundances in the Galaxy, LMC, and SMC is noted. Publication: The Astrophysical Journal Pub Date: January 1985 DOI: 10.1086/162821 Bibcode: 1985ApJ...288..558C Keywords: Cosmic Dust; Cosmic Gases; Interstellar Matter; Magellanic Clouds; Stellar Spectrophotometry; Chemical Composition; Interstellar Extinction; Iue; Milky Way Galaxy; Optical Polarization; Polarization Characteristics; Ubv Spectra; Astrophysics full text sources ADS | data products SIMBAD (51) NED (1) MAST (1) INES (1)

A study of ultraviolet interstellar extinction in and near the core of the 30 Doradus nebula is presented. The pair method is used to determine the shape of the ultraviolet extinction curve, and reddened stars from within 80 pc of the core and unreddened stars from a variety of locations in the Large Magellanic Cloud (LMC) are considered. All stars near the core appear to be reddened by E(B-V) = 0.09-0.16 with an extinction law similar to previous LMC extinction laws. Some stars, including R136a, R145, and R147, are additionally reddened by E(B-V) = 0.18 with a 'nebular-type' extinction law. A model consisting of a layer of 'LMC foreground dust' which affects all of the stars and a deeper layer of 'nebular dust' which affects some of the stars is used for an explanation of the extinction properties. The extinction curves are then applied to the ultraviolet energy distribution of R136a for a determination of its intrinsic continuum shape. Evidence showing that the brightest LMC OB supergiants have intrinsic (B-V) colors and UV-to-visual continuum slopes which are redder than expected is presented.

In this review, we highlight the contributions made by the Swift/UVOT instrument to the understanding of the ultraviolet (UV) attenuation and extinction properties of interstellar dust and provide insight into hot stars and young stellar populations. The study of these two fields is interconnected: UV-bright objects can only be understood if the effects of foreground dust are accounted for, but foreground dust can only be accounted for by studying the properties of UV-bright objects. Decades worth of work have established that the effects of dust on background starlight vary in the ultraviolet, with proposed extinction laws having a wide variety of slopes and a strong “bump” spectroscopic feature at 2175 Å. We show that UVOT is uniquely suited to probe variations in the UV extinction law, specifically because of the uvm2 filter that is centered on the bump and the telescope’s ability to resolve nearby stellar populations. When used in combination with optical and infrared imaging, UVOT can provide strong constraints on variations in the extinction law, both from galaxy to galaxy and within individual galaxies, as well as the properties of young stellar populations. Surveys of UVOT have included the Milky Way, the galaxies of the Local Group, the Local Volume Legacy Survey (LVLS) and two deep fields. All of these are being utilized to provide the most detailed information yet about the UV dust attenuation law and the connection of its variation to underlying physical processes as well as the UV properties of hot stars and young stellar populations.

Using the Hubble Space Telescope/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along 13 new sight lines, increasing the M31 sample to 17. This sample covers a wide area of M31, having galactocentric distances of 5–16 kpc, enabling the analysis of UV extinction curve variations over a large region of an external galaxy similar to the Milky Way with global galactic characteristics such as metallicity for the first time. No correlation is found between the extinction parameters and galactocentric distance, which might be expected if there is a radial metallicity gradient in M31. Most of the new UV extinction curves presented here are significantly different from the average extinction curves of the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC), but the average M31 extinction curve is similar to the average extinction curve in the 30 Dor region of the LMC. The wide range of extinction curves seen in each individual Local Group galaxy suggests that global galactic properties such as metallicity may be less important than the local environmental conditions, such as density, UV radiation field, and shocks along each sight line. The combined behavior of the Milky Way, LMC, SMC, and now M31 UV extinction curves supports the idea that there is a family of curves in the Local Group with overlapping dust grain properties between different galaxies.

view Abstract Citations (194) References (71) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The galactic distribution of interstellar absorption as determined from the Celescope catalog of ultraviolet stellar observations and a new catalog of UBV, H-beta photoelectric observations. Deutschman, W. A. ; Davis, R. J. ; Schild, R. E. Abstract New UBV data for 2846 stars and Hfl photometry for 2099 stars are presented; all stars had previously been observed in the rocket ultraviolet in project Celescope, and ultraviolet magnitudes for them at U2 or U3 are available. The data are combined in an investigation of the ultraviolet interstellar extinction law, with emphasis placed on finding systematic variations in that law as functions of galactic longitude and distance. Our data confirm the previous finding that the ultraviolet extinction law is more variable in U3 (Ae = 1590 A) than in U2 (Ae = 2180 A), and that the U3 extinction is greatest for directions of view along spiral arms. In addition, the interstellar medium appears to be more homogeneous in some directions (e.g., toward Crux) and relatively inhomogeneous in others (Cygnus, Puppis). While our data show little evidence for a distance dependence of extinction in most directions, we do find a significant decrease in ultraviolet extinction at U2 and U3 relative to longer wavelengths over the galactic longitude interval 270 < 1 < 3600. Subject headings: interstellar: matter - photometry - ultraviolet: general Publication: The Astrophysical Journal Supplement Series Pub Date: February 1976 DOI: 10.1086/190359 Bibcode: 1976ApJS...30...97D Keywords: Galactic Structure; H Beta Line; Interstellar Extinction; Star Distribution; Ubv Spectra; Ultraviolet Absorption; Astronomical Catalogs; Astronomical Photometry; Celescopes; Electrophotometry; Milky Way Galaxy; Stellar Spectrophotometry; Astronomy full text sources ADS | data products SIMBAD (2211) GCPD (1)

The mid-infrared (MIR) extinction law in the Large Magellanic Cloud (LMC) at four IRAC bands is derived using the data of the Spitzer/SAGE Program. The derived mean extinctions are A[3.6]/AKs = 0.68±0.03, A[4.5]/AKs = 0.97±0.03, A[5.8]/AKs = 0.54±0.04, and A[8.0]/AKs = 0.58±0.07. The results show that: (1) The extinctions at [3.6], [5.8] and [8.0] of the LMC consist a flat curve, similar to that of the Milky Way (MW) predicted by the interstellar grain model at Rv = 5.5; (2) The extinction at [4.5] is clearly higher than the other three bands, which may be caused by the additional absorption of the 4.27μm CO2 ice and/or the 4.67μm CO ice in the LMC molecular clouds; (3) As far as individual sightlines are concerned, the MIR interstellar extinction law Aλ/AKs in the LMC varies with sightlines as the MW does.

It has recently been shown that the Large Magellanic Cloud (LMC) has a substantial effect on the Milky Way’s stellar halo and stellar streams. Here, we explore how deformations of the Milky Way and LMC’s dark matter haloes affect stellar streams, and whether these effects are observable. In particular, we focus on the Orphan–Chenab (OC) stream which passes particularly close to the LMC and spans a large portion of the Milky Way’s halo. We represent the Milky Way–LMC system using basis function expansions that capture their evolution in an N-body simulation. We present the properties of this system, such as the evolution of the densities and force fields of each galaxy. The OC stream is evolved in this time-dependent, deforming potential, and we investigate the effects of the various moments of the Milky Way and the LMC. We find that the simulated OC stream is strongly influenced by the deformations of both the Milky Way and the LMC and that this effect is much larger than current observational errors. In particular, the Milky Way dipole has the biggest impact on the stream, followed by the evolution of the LMC’s monopole, and the LMC’s quadrupole. Detecting these effects would confirm a key prediction of collisionless, cold dark matter, and would be a powerful test of alternative dark matter and alternative gravity models.

The Small Magellanic Cloud (SMC) shows a large variation in ultraviolet (UV) dust extinction curves, ranging from Milky Way (MW) like to significantly steeper curves with no detectable 2175 Å bump. This result is based on a sample of only nine sight lines. From Hubble Space Telescope Space Telescope Imaging Spectrograph and IUE spectra of OB stars, we have measured UV extinction curves along 32 SMC sight lines where eight of these curves were published previously. We find 16 sight lines with steep extinction with no detectable 2175 Å bump, four sight lines with MW-like extinction with a detectable 2175 Å bump, two sight lines with fairly flat UV extinction and weak/absent 2175 Å bumps, and 10 sight lines with unreliable curves due to low SMC dust columns. Our expanded sample shows that the sight lines with and without the 2175 Å bump are located throughout the SMC and not limited to specific regions. The average extinction curve of the 16 bump-less sight lines is very similar to the previous average based on four sight lines. We find no correlation between dust column and the strength of the 2175 Å bump. We test the hypothesis that the 2175 Å bump is due to the same dust grains that are responsible for the mid-infrared carbonaceous (polycyclic aromatic hydrocarbon) emission features and find they are correlated, confirming recent work in the MW. Overall, the slope of the UV extinction increases as the amplitudes of the 2175 Å bump and far-ultraviolet curvature decrease. Finally, the UV slope is correlated with N(H i)/A(V) and the 2175 Å bump and nonlinear far-ultraviolet rise amplitudes are anticorrelated with N(H i)/A(V).

In a companion paper by Koposov et al., RR Lyrae from \textit{Gaia} Data Release 2 are used to demonstrate that stars in the Orphan stream have velocity vectors significantly misaligned with the stream track, suggesting that it has received a large gravitational perturbation from a satellite of the Milky Way. We argue that such a mismatch cannot arise due to any realistic static Milky Way potential and then explore the perturbative effects of the Large Magellanic Cloud (LMC). We find that the LMC can produce precisely the observed motion-track mismatch and we therefore use the Orphan stream to measure the mass of the Cloud. We simultaneously fit the Milky Way and LMC potentials and infer that a total LMC mass of $1.38^{+0.27}_{-0.24} \times10^{11}\,\rm{M_\odot}$ is required to bend the Orphan Stream, showing for the first time that the LMC has a large and measurable effect on structures orbiting the Milky Way. This has far-reaching consequences for any technique which assumes that tracers are orbiting a static Milky Way. Furthermore, we measure the Milky Way mass within 50 kpc to be $3.80^{+0.14}_{-0.11}\times10^{11} M_\odot$. Finally, we use these results to predict that, due to the reflex motion of the Milky Way in response to the LMC, the outskirts of the Milky Way's stellar halo should exhibit a bulk, upwards motion.

We use the APOSTLE ΛCDM cosmological hydrodynamical simulations of the Local Group to study the recent accretion of massive satellites into the halo of Milky Way (MW)-sized galaxies. These systems are selected to be close analogues to the Large Magellanic Cloud (LMC), the most massive satellite of the MW. The simulations allow us to address, in a cosmological context, the impact of the Clouds on the MW, including the contribution of Magellanic satellites to the MW satellite population, and the constraints placed on the Galactic potential by the motion of the LMC. We show that LMC-like satellites are twice more common around Local Group-like primaries than around isolated haloes of similar mass; these satellites come from large turnaround radii and are on highly eccentric orbits whose velocities at first pericentre are comparable with the primary’s escape velocity. This implies $V_{\rm esc}^{\rm MW} (50$ kpc) ∼ 365 km s−1, a strong constraint on Galactic potential models. LMC analogues contribute about two satellites with $M_*\gt 10^5\, \mathrm{ M}_\odot$, having thus only a mild impact on the luminous satellite population of their hosts. At first pericentre, LMC-associated satellites are close to the LMC in position and velocity, and are distributed along the LMC’s orbital plane. Their orbital angular momenta roughly align with the LMC’s, but, interestingly, they may appear to ‘counter-rotate’ the MW in some cases. These criteria refine earlier estimates of the LMC association of MW satellites: only the SMC, Hydrus1, Car3, Hor1, Tuc4, Ret2, and Phoenix2 are compatible with all criteria. Carina, Grus2, Hor2, and Fornax are less probable associates given their large LMC relative velocity.

We study the orbits of dwarf galaxies in the combined presence of the Milky Way and Large Magellanic Cloud (LMC) and find six dwarfs that were likely accreted with the LMC (Car 2, Car 3, Hor 1, Hyi 1, Phe 2, and Ret 2), in addition to the Small Magellanic Cloud (SMC), representing strong evidence of dwarf galaxy group infall. This procedure depends on the gravitational pull of the LMC, allowing us to place a lower bound on the Cloud’s mass of $M_{\rm LMC} \gt 1.24\times 10^{11} \, \mathrm{M}_\odot$ if we assume that these are LMC satellites. This mass estimate is validated by applying the technique to a cosmological zoom-in simulation of a Milky Way-like galaxy with an LMC analogue where we find that while this lower bound may be overestimated, it will improve in the future with smaller observational errors. We apply this technique to dwarf galaxies lacking radial velocities and find that Eri 3 has a broad range of radial velocities for which it has a significant chance (&amp;gt;0.4) of having been bound to the Cloud. We study the non-Magellanic classical satellites and find that Fornax has an appreciable probability of being an LMC satellite if the LMC is sufficiently massive ($\text{$\sim$} 2.5\times 10^{11} \, \mathrm{M}_\odot$). In addition, we explore how the orbits of Milky Way satellites change in the presence of the LMC and find a significant change for several objects. Finally, we find that the dwarf galaxies likely to be LMC satellites are slightly smaller than Milky Way satellites at a fixed luminosity, possibly due to the different tidal environments they have experienced.

Indications of disequilibrium throughout the Milky Way (MW) highlight the need for compact, flexible, non-parametric descriptions of phase–space distributions of galaxies. We present a new representation of the current dark matter (DM) distribution and potential derived from N-body simulations of the MW and Large Magellanic Cloud (LMC) system using basis function expansions (BFEs). We incorporate methods to maximize the physical signal in the representation. As a result, the simulations of 108 DM particles representing the distorted MW(MW+LMC) system can be described by ∼236(2067) coefficients. We find that the LMC induces asymmetric perturbations (odd l, m) to the MW’s halo, which are inconsistent with oblate, prolate, or triaxial halos. Furthermore, the energy in high order even modes (l, m &gt; 2) is similar to average triaxial halos found in cosmological simulations. As such, the response of the MW’s halo to the LMC must be accounted for in order to recover the imprints of its assembly history. The LMC causes the outer halo (&gt;30 kpc) to shift from the disk center of mass (COM) by ∼15–25 kpc at present day, manifesting as a dipole in the BFE and in the radial velocities of halo stars. The shift depends on the LMC’s infall mass, the distortion of the LMC’s halo and the MW halo response.Within 30 kpc, halo tracers are expected to orbit the COM of the MW’s disk, regardless of LMC infall mass. The LMC’s halo is also distorted by MW tides; we discuss the implications for its mass loss and the subsequent effects on current Magellanic satellites.

We predict and compare the distributions and properties of hypervelocity stars (HVSs) ejected from the centres of the Milky Way (MW) and the Large Magellanic Cloud (LMC). In our model, HVSs are ejected at a constant rate – equal in both galaxies – via the Hills mechanism and are propagated in a combined potential, where the LMC orbits the MW on its first infall. By selecting $m \gt 2\, \mathrm{M_\odot }$ HVSs well separated from the Magellanic Clouds and Galactic mid-plane, we identify mock HVSs which would stand out from ordinary stars in the stellar halo in future data releases from the Gaia satellite and the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). We find that in these deep surveys, LMC HVSs will outnumber MW ones by a factor of ∼2.5, as HVSs can more easily escape from the shallower potential of the LMC. At an assumed HVS ejection rate of $10^{-4} \, \mathrm{yr^{-1}}$, HVSs detectable in the final Gaia data release and LSST from the LMC (MW) will number $125_{-12}^{+11}$ ($50_{-8}^{+7}$) and $140_{-11}^{+10}$ ($42_{-7}^{+6}$), respectively. The MW and LMC HVS populations show different kinematics and spatial distributions. While LMC HVSs have more modest total velocities and larger Galactocentric distances clustered around those of the LMC itself, HVSs from the MW show broader distributions, including a prominent high-velocity tail above $500 \, \mathrm{km \ s^{-1}}$ that contains at least half of the stars. These predictions are robust against reasonable variation of the Galactic potential and of the LMC central black hole mass.

Ten early-type supergiants in the Large Magellanic Cloud (LMC) have been observed with the International Ultraviolet Explorer (IUE). The spectra (1150-3200 A) are shown, and their photometric properties are discussed. It is confirmed that the LMC interstellar extinction law for these stars deviates significantly from the average galactic law in the sense that the 2200 A feature is deficient in strength and that, in the far-ultraviolet (wavelength less than 2000 A), the observed LMC extinction law is significantly above the galactic curve.