A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond
Maria-Rosa L. Cioni, Martino Romaniello, Richard I. Anderson
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The Messenger 181 – Quarter 3 | 2020
Report on the ESO Workshopheld at ESO Headquarters, Garching, Germany, 9–13 September 2019
A Synoptic View of the Magellanic Clouds: VMC, Gaia, and Beyond
Maria-Rosa L. Cioni Martino Romaniello Richard I. Anderson Leibniz-Institut für Astrophysik Potsdam (AIP), Germany ESO
The year 2019 marked the quincente-nary of the arrival in the southern hemi-sphere of Ferdinand Magellan, the namesake of the Magellanic Clouds, our nearest example of dwarf galaxies in the early stages of a minor merging (cid:72)(cid:89)(cid:72)(cid:81)(cid:87)(cid:17)(cid:3)(cid:55)(cid:75)(cid:72)(cid:86)(cid:72)(cid:3)(cid:74)(cid:68)(cid:79)(cid:68)(cid:91)(cid:76)(cid:72)(cid:86)(cid:3)(cid:75)(cid:68)(cid:89)(cid:72)(cid:3)(cid:69)(cid:72)(cid:72)(cid:81)(cid:3)(cid:314)(cid:85)(cid:80)(cid:79)(cid:92)(cid:3) established as laboratories for the study of variable stars, stellar evolution, and galaxy interaction, as well as being anchors for the extragalactic distance scale. The goal of this conference was to provide fertile ground for shaping future research related to the Magellanic Clouds by combining state-of-the-art results based on advanced observa-tional programmes with discussions of (cid:87)(cid:75)(cid:72)(cid:3)(cid:75)(cid:76)(cid:74)(cid:75)(cid:79)(cid:92)(cid:3)(cid:80)(cid:88)(cid:79)(cid:87)(cid:76)(cid:83)(cid:79)(cid:72)(cid:91)(cid:72)(cid:71)(cid:3)(cid:90)(cid:76)(cid:71)(cid:72)(cid:16)(cid:314)(cid:72)(cid:79)(cid:71)(cid:3)(cid:86)(cid:83)(cid:72)(cid:70) -troscopic surveys that will come online in the 2020s.Motivations
Observational access to the Magellanic Clouds system was one of the key scien- (cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:67)(cid:81)(cid:72)(cid:85)(cid:68)(cid:81)(cid:82)(cid:3)(cid:83)(cid:78)(cid:3)(cid:65)(cid:84)(cid:72)(cid:75)(cid:67)(cid:3)(cid:75)(cid:64)(cid:81)(cid:70)(cid:68)(cid:3)(cid:83)(cid:68)(cid:75)(cid:68)(cid:82)(cid:66)(cid:78)(cid:79)(cid:68)(cid:82)(cid:3)(cid:72)(cid:77)(cid:3) the southern hemisphere, which led to the foundation of ESO itself. Almost 60 years later, the Magellanic Clouds are still very much at the centre of the discourse, pro-viding fundamental insight into several hot research topics. The Magellanic Clouds are our nearest examples of dwarf galax-ies at an early stage of a minor merger event. The distribution of their stars and gas provides evidence of an active his-tory of formation and interaction. Thanks to wide and deep photometric observa-tions obtained during the last decade, we have been able to describe the star for-mation history and the geometry of the Magellanic Clouds at an unprecedented level of detail. The VISTA near-infrared ESO Public Survey of the Magellanic Clouds system (VMC) has played a major role in this endeavour. In this workshop, the most interesting discoveries emerging from the VMC and other contemporary multi-wavelength surveys were discussed. These results have cemented stellar populations as important diagnostics of galaxy proper-ties. Cepheid stars have, for example, revealed the three-dimensional structure of the system, giant stars have shown (cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106)(cid:66)(cid:64)(cid:77)(cid:83)(cid:75)(cid:88)(cid:3)(cid:68)(cid:87)(cid:83)(cid:68)(cid:77)(cid:67)(cid:68)(cid:67)(cid:3)(cid:79)(cid:78)(cid:79)(cid:84)(cid:75)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:82)(cid:11)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3) blue horizontal branch stars have indi-cated protuberances and possible streams in the outskirts of the galaxies. The complementary view provided by (cid:49)(cid:49)(cid:368)(cid:43)(cid:88)(cid:81)(cid:64)(cid:68)(cid:3)(cid:82)(cid:83)(cid:64)(cid:81)(cid:82)(cid:3)(cid:82)(cid:71)(cid:78)(cid:86)(cid:82)(cid:3)(cid:72)(cid:77)(cid:82)(cid:83)(cid:68)(cid:64)(cid:67)(cid:3)(cid:81)(cid:68)(cid:70)(cid:84)(cid:75)(cid:64)(cid:81)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3) ellipsoidal systems. The analysis of the star formation history suggests that the Small Magellanic Cloud (SMC) formed half of its mass prior to about 6 Gyr ago, while a proper motion map reveals tidal features, for example, behind the main body of the galaxy and along the line of sight. The Magellanic Clouds may have arrived at the Milky Way system only recently, together with associated satellite galaxies, and may be more massive than we used to think. The chemical informa-tion that was derived, albeit for limited types and numbers of stars, is highly valuable for understanding the internal structure of the galaxies as well as the geometry and chemical evolution of the system — for example, the origin of the (cid:44)(cid:64)(cid:70)(cid:68)(cid:75)(cid:75)(cid:64)(cid:77)(cid:72)(cid:66)(cid:3)(cid:50)(cid:83)(cid:81)(cid:68)(cid:64)(cid:76)(cid:13)(cid:3)(cid:37)(cid:78)(cid:81)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:83)(cid:72)(cid:76)(cid:68)(cid:11)(cid:3) astronomers are beginning to link age and metallicity distributions with the kine-matics and structure of stellar popula-tions, thereby deciphering the formation and evolution of the Magellanic Clouds in great detail.Within the next year, important observing programmes targeting the Magellanic Clouds will reach completion and provide unique datasets through which the study of the stellar populations will unfold. Moreover, the imminent release of new Gaia data is expected to shed new light on the precision to which stellar popula-tions parameters can be characterised. The Magellanic Clouds remain a unique astrophysical laboratory, for investiga-tions of stellar evolution, star clusters, the distance scale and the measurement of the local value of the Hubble constant to high precision. Future developments (cid:69)(cid:78)(cid:66)(cid:84)(cid:82)(cid:3)(cid:78)(cid:77)(cid:3)(cid:84)(cid:82)(cid:72)(cid:77)(cid:70)(cid:3)(cid:86)(cid:72)(cid:67)(cid:68)(cid:12)(cid:106)(cid:68)(cid:75)(cid:67)(cid:11)(cid:3)(cid:71)(cid:72)(cid:70)(cid:71)(cid:12)(cid:76)(cid:84)(cid:75)(cid:83)(cid:72)(cid:79)(cid:75)(cid:68)(cid:87)(cid:3) spectrographs and powerful images to obtain a robust chemical understanding of the system and use stellar population diagnostics across the Hertzsprung- Russell diagram with unprecedented pre-cision. Most of these developments will culminate in the early 2020s and discus-sions on how to formulate the most rele- (cid:85)(cid:64)(cid:77)(cid:83)(cid:3)(cid:82)(cid:66)(cid:72)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:80)(cid:84)(cid:68)(cid:82)(cid:83)(cid:72)(cid:78)(cid:77)(cid:82)(cid:3)(cid:64)(cid:81)(cid:68)(cid:3)(cid:64)(cid:75)(cid:81)(cid:68)(cid:64)(cid:67)(cid:88)(cid:3) advanced.
Summaries of talks and highlights from sessions
The workshop revolved around eight (cid:82)(cid:66)(cid:72)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:82)(cid:68)(cid:82)(cid:82)(cid:72)(cid:78)(cid:77)(cid:82)(cid:3)(cid:64)(cid:83)(cid:3)(cid:86)(cid:71)(cid:72)(cid:66)(cid:71)(cid:3)(cid:64)(cid:3)(cid:83)(cid:78)(cid:83)(cid:64)(cid:75)(cid:3)(cid:78)(cid:69)(cid:3)
64 talks were presented and a summary is given below. There were also 28 post-ers complementing each session. A vote was held to select the best among them and the winner was the poster by Raphael Oliveira on “Age and metallicity gradients in the Magellanic Bridge with the VISCACHA survey”, which received a prize — a framed photograph of the 30 Doradus press-release image that was produced by the VMC survey.
The Magellanic Clouds in context
Joss Bland-Hawthorn opened the meet-ing by highlighting the importance of the Magellanic Clouds as galaxies that have contributed to the growth of the Milky Way. Recent results on the gas distribu-tion, the internal motions of stars and their chemical composition reinforce the Clouds as a place to study many astro-physical processes under different envi-ronmental conditions. The orbital history of the Magellanic Clouds, which is re- (cid:107)(cid:68)(cid:66)(cid:83)(cid:68)(cid:67)(cid:3)(cid:72)(cid:77)(cid:3)(cid:83)(cid:71)(cid:68)(cid:72)(cid:81)(cid:3)(cid:82)(cid:83)(cid:64)(cid:81)(cid:3)(cid:69)(cid:78)(cid:81)(cid:76)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:71)(cid:72)(cid:82)(cid:83)(cid:78)(cid:81)(cid:88)(cid:11)(cid:3)(cid:66)(cid:64)(cid:77)(cid:3)(cid:65)(cid:68)(cid:3)(cid:84)(cid:82)(cid:68)(cid:67)(cid:3)(cid:83)(cid:78)(cid:3)(cid:68)(cid:82)(cid:83)(cid:64)(cid:65)(cid:75)(cid:72)(cid:82)(cid:71)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)
Milky Way and to probe the physics of the dark matter halo. Subsequently, Laura Sales reminded us that Lambda-Cold-Dark-Matter ( (cid:82)
CDM) substructures around dwarf galaxies indicate that the Large Magellanic Cloud (LMC) must have brought along several of its own dwarf satellites. She argued that, as a result of their recent infall, the dark and baryonic (cid:76)(cid:64)(cid:83)(cid:83)(cid:68)(cid:81)(cid:3)(cid:86)(cid:78)(cid:84)(cid:75)(cid:67)(cid:3)(cid:69)(cid:78)(cid:75)(cid:75)(cid:78)(cid:86)(cid:3)(cid:64)(cid:3)(cid:82)(cid:79)(cid:68)(cid:66)(cid:72)(cid:106)(cid:66)(cid:3)(cid:79)(cid:64)(cid:83)(cid:71)(cid:3)(cid:78)(cid:77)(cid:3) the sky. Indeed, the combination of deep photometry and accurate astrometry from Gaia has revelaed that several ultra-faint dwarfs, together with some low-mass classical dwarfs, are consistent with having been accreted as part of the Astronomical News
DOI: 10.18727/0722-6691/5211 The Messenger 181 – Quarter 3 | 2020
LMC group. This also implies a large LMC virial mass at infall ( M (cid:174)(cid:3)(cid:18)(cid:368)(cid:151)(cid:368)(cid:16)(cid:15) (cid:368) M (cid:3692) ) (cid:64)(cid:77)(cid:67)(cid:3)(cid:64)(cid:3)(cid:67)(cid:72)(cid:81)(cid:68)(cid:66)(cid:83)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:43)(cid:44)(cid:34)(cid:3)(cid:78)(cid:77)(cid:3) the star formation history of its satellites. Elena Sacchi concluded that the star for-mation history of ultra-faint dwarfs asso-ciated with the Magellanic Clouds differs from that of similar objects associated with the Milky Way.Satellites that are likely members of the Magellanic Clouds are characterised by bright horizontal branches, dispersed red giant branches and a star formation his-tory that stopped 1–2 Gyr earlier than in ultra-dwarf systems of the Milky Way. Ethan Jahn illustrated, using zoom-in cosmological simulations to study LMC-mass analogues, that tidal interactions with the central galaxy allow the retention of more substructure than in Milky Way-mass hosts, but similarly cause tidal strip-ping of satellites, suggesting that future kinematical studies will reveal additional satellites associated with the Clouds. Alice Minelli addressed both the LMC and the Sagittarius dwarf galaxy, the lat-ter being in a more advanced stage of gravitational interaction with the Milky Way than the LMC is. A high-resolution spectroscopic study of 25–30 red giant branch stars per galaxy, measuring the abundance of alpha-, light-, Fe-peak and neutron- capture elements, showed that the two dwarfs experienced a very similar chemical enrichment history despite their current differences, i.e., the LMC still contains gas and presents ongoing star formation while the Sagittarius dwarf is predominantly an old system deprived of gas. Marcel Pawlowski’s review dealt with the plane of satellite galaxies problem. Satellite galaxies of the Local Group arrange themselves in narrow structures, with the Magellanic Clouds associated with the Vast Polar Structure, and the Magellanic Stream curiously aligned with other structures, with signs of kinematic correlation (supported by Gaia proper motions) indicative of corotation. Planes of satellites are not common in (cid:82) CDM simulations and their potential origins include the following: accretions from (cid:79)(cid:81)(cid:68)(cid:69)(cid:68)(cid:81)(cid:81)(cid:68)(cid:67)(cid:3)(cid:67)(cid:72)(cid:81)(cid:68)(cid:66)(cid:83)(cid:72)(cid:78)(cid:77)(cid:82)(cid:3)(cid:7)(cid:106)(cid:75)(cid:64)(cid:76)(cid:68)(cid:77)(cid:83)(cid:82)(cid:8)(cid:11)(cid:3)(cid:70)(cid:81)(cid:78)(cid:84)(cid:79)(cid:3) infall or a tidal nature of the dwarf galax-ies — there are elements both in favour and against such possibilities.
Evolution of stars and star clusters in the Magellanic Clouds
The meeting continued with a rich session devoted to the evolution of stars and star clusters, since the Magellanic Clouds provide, in this context, the best samples at sub-solar metallicities. Leo Girardi dis-cussed the calibration of overshooting in main-sequence stars and the evolution of asymptotic giant branch stars, which are critical to determining the nuclear fuel burnt by blue and red stars, and model spectra of 0.1–5 Gyr-old distant galaxies. This work is usually performed in respect of stars that are members of star clus- (cid:83)(cid:68)(cid:81)(cid:82)(cid:11)(cid:3)(cid:86)(cid:71)(cid:68)(cid:81)(cid:68)(cid:3)(cid:82)(cid:83)(cid:68)(cid:75)(cid:75)(cid:64)(cid:81)(cid:3)(cid:81)(cid:78)(cid:83)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:79)(cid:75)(cid:64)(cid:88)(cid:82)(cid:3)(cid:64)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106) -cant role. Field stars, however, where the star formation history is derived, repre-sent a promising input to the calibration of asymptotic giant branch models that also take pulsation and mass-loss into account. The phenomenon of multiple populations, observed in star clusters of different ages, was reviewed by Nate Bastian. The split main sequence in young (< 1 Gyr old) clusters and the extended main- sequence turnoff in clusters < 2 Gyr old can both be explained using rotation as the dominant mechanism; the large frac-tion of rapidly rotating stars is supported by a large (~ 60%) fraction of Be stars in these clusters. Seth Gossage demon-strated that stellar evolutionary models that include stellar rotation are able to account for the majority of extendend main-sequence turnoff morphologies. However, other effects like age spreads and braking are not ruled out. Andrea Dupree showed that important con-straints to the models of these effects are obtained from high- resolution spectro-scopic observations of H (cid:95) and He I. Fur- (cid:83)(cid:71)(cid:68)(cid:81)(cid:76)(cid:78)(cid:81)(cid:68)(cid:11)(cid:3)(cid:40)(cid:85)(cid:64)(cid:77)(cid:3)(cid:34)(cid:64)(cid:65)(cid:81)(cid:68)(cid:81)(cid:64)(cid:12)(cid:3)(cid:57)(cid:72)(cid:81)(cid:72)(cid:3)(cid:66)(cid:78)(cid:77)(cid:106)(cid:81)(cid:76)(cid:68)(cid:67)(cid:3) that neither massive stars nor low-mass stars in young clusters show element abundance variations. On the contrary, a spread in light element abundances (for example, N, Na, C, O, Mg, Al) is likely responsible for the split red giant branches in older clusters. Silvia Martocchia showed the results of a study of about 20 massive (> 10 M (cid:4330) ) star clusters in the Magellanic (cid:34)(cid:75)(cid:78)(cid:84)(cid:67)(cid:82)(cid:3)(cid:86)(cid:71)(cid:68)(cid:81)(cid:68)(cid:11)(cid:3)(cid:69)(cid:78)(cid:81)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:83)(cid:72)(cid:76)(cid:68)(cid:11)(cid:3)(cid:76)(cid:84)(cid:75)(cid:83)(cid:72)(cid:79)(cid:75)(cid:68)(cid:3) populations were found in clusters as young as 2 Gyr. A larger abundance spread was found in older clusters com- pared to younger ones, while age differ-ences within a given cluster are < 20 Myr. Complicating the picture, Paul Goudfrooij showed that the faint main sequence of young LMC star cluters is characterised by a kink which is not reproduced by stel-lar isochrones. This is probably associ-ated with a sudden decrease of tempera-ture resulting from an expansion of the convective envelope in stars with masses < 1.45 M (cid:3692) , at the metallicity of the LMC, which may cause braking. Interestingly, the main sequence below the kink of sev-eral clusters is consistent with that of a single stellar population.The properties of the high-mass popula-tions of the Clouds were reviewed by Chris Evans who emphasised the results obtained from the VLT-FLAMES Tarantula Survey. In particular, it was shown that the percentage of binary stars is similar to that in the Galaxy, that it extends to (cid:33)(cid:368)(cid:82)(cid:83)(cid:64)(cid:81)(cid:82)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3)(cid:83)(cid:71)(cid:68)(cid:81)(cid:68)(cid:3)(cid:72)(cid:82)(cid:3)(cid:64)(cid:77)(cid:3)(cid:68)(cid:87)(cid:66)(cid:68)(cid:82)(cid:82)(cid:3)(cid:78)(cid:69)(cid:3) massive stars in the region of 30 Doradus with respect to predictions based on the initial mass function. Future observational projects will target SMC massive stars in the ultraviolet to support models at low metallicity. Joachim Bestenlehner focused on the star cluster R136 at the core of 30 Doradus. The cluster age peaks at 1.2 Myr and its most massive stars ( M > 100 M (cid:3692) ) account for a quarter (cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:72)(cid:78)(cid:77)(cid:72)(cid:82)(cid:72)(cid:77)(cid:70)(cid:3)(cid:107)(cid:84)(cid:87)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:17)(cid:14)(cid:18)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:76)(cid:68)(cid:66)(cid:71)(cid:64)(cid:77) -ical feedback. A comprehensive catalogue of 1405 red, 217 yellow and 1369 blue supergiant stars across the SMC was presented by Ming Yang. It stemmed from multi-wavelength observations, from ultraviolet to far-infrared with 29 different (cid:106)(cid:75)(cid:83)(cid:68)(cid:81)(cid:82)(cid:11)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:66)(cid:78)(cid:76)(cid:65)(cid:72)(cid:77)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:86)(cid:72)(cid:83)(cid:71)(cid:3)(cid:38)(cid:64)(cid:72)(cid:64)(cid:3) data to identify SMC members down to a minimum mass of 6–7 M (cid:3692) . Among the intermediate-mass (3–10 M (cid:3692) ) red super-giants are also Cepheids for which ages strongly depend on model physics — for example, including stellar rotation makes the stars older. Richard Anderson argued that new tests confronting dynamical and evolutionary timescales for Cepheid members of star clusters are needed. Star formation history and chemistry across the Magellanic system
Andrew Cole opened the third section of the meeting with a review of the star Astronomical News Cioni M.-R. L. et al., Report on the Workshop “A Synoptic View of the Magellanic Clouds”5
The Messenger 181 – Quarter 3 | 2020
Figure 1.
Conference photo. formation history of the Magellanic Clouds. He highlighted that these nearby galaxies could be both a blessing and a curse, in that they provide an extremely rich population of stars across a Hubble time on the one hand, and on the other hand a level of detail over a large area of (cid:82)(cid:74)(cid:88)(cid:3)(cid:82)(cid:84)(cid:66)(cid:71)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:11)(cid:3)(cid:102)(cid:77)(cid:78)(cid:3)(cid:82)(cid:72)(cid:77)(cid:70)(cid:75)(cid:68)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:3)(cid:72)(cid:82)(cid:3)(cid:68)(cid:85)(cid:68)(cid:81)(cid:3) going to be totally representative”. The LMC had a strong initial phase of star for-mation that then declined, picking up again 3–5 Gyr ago, while the SMC started forming stars vigorously only 5 Gyr ago.Star formation histories derived from deep photometry were presented by Tomás Ruiz- Lara from the application of a well- (cid:68)(cid:82)(cid:83)(cid:64)(cid:65)(cid:75)(cid:72)(cid:82)(cid:71)(cid:68)(cid:67)(cid:3)(cid:66)(cid:78)(cid:75)(cid:78)(cid:84)(cid:81)(cid:12)(cid:76)(cid:64)(cid:70)(cid:77)(cid:72)(cid:83)(cid:84)(cid:67)(cid:68)(cid:3)(cid:67)(cid:72)(cid:64)(cid:70)(cid:81)(cid:64)(cid:76)(cid:3)(cid:106)(cid:83) -ting technique. Additonal episodes of star (cid:69)(cid:78)(cid:81)(cid:76)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:86)(cid:68)(cid:81)(cid:68)(cid:3)(cid:72)(cid:67)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:68)(cid:67)(cid:11)(cid:3)(cid:64)(cid:82)(cid:3)(cid:86)(cid:68)(cid:75)(cid:75)(cid:3)(cid:64)(cid:82)(cid:3)(cid:67)(cid:72)(cid:69) -ferences in the building up of particular regions. The extremes of the LMC bar appear younger and more metal rich than the disc which appears metal poor, but older in the south than in the north. Alessio Mucciarelli reviewed the chemical information obtained from spectroscopic investigations at low resolution (based on the CaII triplet method for a general as- sessment of the overall metallicity) and at high resolution (based on the abundance of other elements such as Ba and Eu). Different studies agree on the lower [ (cid:95) /Fe] abundance in the LMC compared to that in the Milky Way, which also indicates a lower star formation rate. However, there is disagreement on the slope of [ (cid:95) /Fe] as a function of [Fe/H] and on the position of the [ (cid:95) /Fe] knee, marking the onset of the (cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:88)(cid:79)(cid:68)(cid:3)(cid:40)(cid:64)(cid:3)(cid:82)(cid:84)(cid:79)(cid:68)(cid:81)(cid:77)(cid:78)(cid:85)(cid:64)(cid:68)(cid:13)(cid:3)(cid:44)(cid:64)(cid:83)(cid:71)(cid:72)(cid:68)(cid:84)(cid:3)
Van der Swaelmen presented the analysis of FLAMES spectra of red giant branch (cid:82)(cid:83)(cid:64)(cid:81)(cid:82)(cid:3)(cid:72)(cid:77)(cid:3)(cid:64)(cid:3)(cid:69)(cid:68)(cid:86)(cid:3)(cid:43)(cid:44)(cid:34)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:82)(cid:13)(cid:3)(cid:39)(cid:68)(cid:3)(cid:69)(cid:78)(cid:84)(cid:77)(cid:67)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3) [Mg, O/Fe] are indeed lower in the LMC than in the Milky Way, while [Si, Ca, Ti/Fe] are similar. This suggests that the chemi-cal history of the LMC was dominated by type Ia supernovae and intermediate- (cid:76)(cid:64)(cid:82)(cid:82)(cid:3)(cid:83)(cid:88)(cid:79)(cid:68)(cid:3)(cid:40)(cid:40)(cid:3)(cid:82)(cid:84)(cid:79)(cid:68)(cid:81)(cid:77)(cid:78)(cid:85)(cid:64)(cid:68)(cid:11)(cid:3)(cid:86)(cid:72)(cid:83)(cid:71)(cid:78)(cid:84)(cid:83)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106) - (cid:66)(cid:64)(cid:77)(cid:83)(cid:3)(cid:67)(cid:72)(cid:69)(cid:69)(cid:68)(cid:81)(cid:68)(cid:77)(cid:66)(cid:68)(cid:82)(cid:3)(cid:64)(cid:76)(cid:78)(cid:77)(cid:70)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:83)(cid:71)(cid:81)(cid:68)(cid:68)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:82)(cid:13) Large-scale infrared surveys have allowed (cid:83)(cid:71)(cid:68)(cid:3)(cid:72)(cid:67)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:78)(cid:69)(cid:3)(cid:70)(cid:64)(cid:75)(cid:64)(cid:87)(cid:88)(cid:12)(cid:86)(cid:72)(cid:67)(cid:68)(cid:3)(cid:82)(cid:64)(cid:76)(cid:79)(cid:75)(cid:68)(cid:82)(cid:3) of young stars, as explained in Joana Oliveira’s presentation. This is a crucial step in studying environmental depend-encies on star formation and early stellar evolution in order to understand the role of metallicity and galactic structure. In par-ticular, LMC young stellar objects show (cid:71)(cid:72)(cid:70)(cid:71)(cid:3)(cid:64)(cid:66)(cid:66)(cid:81)(cid:68)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:81)(cid:64)(cid:83)(cid:68)(cid:82)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106)(cid:66)(cid:64)(cid:77)(cid:83)(cid:3)(cid:75)(cid:72)(cid:70)(cid:71)(cid:83) -curve variations, while the distributions of upper- and pre-main sequence stars support hierarchical and dust heating substructures. Clifton Johnson showed the powerful impact of the combination of observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope (HST) on studies of pre-main sequence stars and their environment in the Magellanic (cid:34)(cid:75)(cid:78)(cid:84)(cid:67)(cid:82)(cid:13)(cid:3)(cid:51)(cid:71)(cid:68)(cid:3)(cid:82)(cid:83)(cid:64)(cid:81)(cid:3)(cid:69)(cid:78)(cid:81)(cid:76)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:68)(cid:69)(cid:106)(cid:66)(cid:72)(cid:68)(cid:77)(cid:66)(cid:88)(cid:3)(cid:78)(cid:69)(cid:3) molecular clouds in the SMC (~ 2% with 0.5 dex spread) appears consistent with that in the Milky Way and shows a corre-lation with cloud age.
Gas and dust within the Magellanic system (cid:45)(cid:64)(cid:78)(cid:76)(cid:72)(cid:3)(cid:44)(cid:66)(cid:34)(cid:75)(cid:84)(cid:81)(cid:68)(cid:12)(cid:38)(cid:81)(cid:72)(cid:69)(cid:106)(cid:83)(cid:71)(cid:82)(cid:3)(cid:79)(cid:81)(cid:68)(cid:82)(cid:68)(cid:77)(cid:83)(cid:68)(cid:67)(cid:3) an overview of the atomic gas in the Magellanic system, including the Magellanic Bridge, Stream and Leading Arm, which are predominantly gaseous features. A spectacular map of the SMC, with a spatial resolution 10 times higher than that of previous maps, shows a cold (cid:7)(cid:51)(cid:3)(cid:27)(cid:3)(cid:19)(cid:15)(cid:15)(cid:3)(cid:42)(cid:8)(cid:3)(cid:70)(cid:64)(cid:82)(cid:3)(cid:78)(cid:84)(cid:83)(cid:107)(cid:78)(cid:86)(cid:3)(cid:7)(cid:18)(cid:20)(cid:108)(cid:21)(cid:15)(cid:3)(cid:74)(cid:76)(cid:3)(cid:82) -1 ), about 40% of which is beyond escape (cid:85)(cid:68)(cid:75)(cid:78)(cid:66)(cid:72)(cid:83)(cid:88)(cid:13)(cid:3)(cid:51)(cid:71)(cid:72)(cid:82)(cid:3)(cid:72)(cid:76)(cid:79)(cid:75)(cid:72)(cid:68)(cid:82)(cid:3)(cid:64)(cid:77)(cid:3)(cid:39)(cid:40)(cid:3)(cid:76)(cid:64)(cid:82)(cid:82)(cid:3)(cid:107)(cid:84)(cid:87)(cid:3)(cid:78)(cid:69)(cid:3) M (cid:3692) yr –1 , 2–10 times larger than the rate of star formation in the SMC, which is therefore likely to quench in 0.2–3 Gyr. The rotation curve resembles that of a rotating disc. Both cold and ionised gas (for example, Si I, Si II, H (cid:95) ) reside in both the Stream and the Leading Arm. Andrew Fox highlighted the dual chemical origin of the Stream, from both the LMC and the SMC, whilst abundances in the Leading Arm suggest an SMC origin; their varia-tion corroborates a scenario in which the different clumps represent shredded dwarfs accreted as part of the Magellanic group. The average temperature of HI clouds is 30 K and there seems to be a clear correspondence between the loca-tion of these clouds and that of the small clumps of CO emission and/or molecular gas, as revelaed by ALMA observations and presented by Katie Jameson. Kat Barger provided an overview of the signif-icant amount of ionising debris surround-ing the Magellanic Clouds as revealed by the highest sensitivity emission-line Wisconsin H (cid:95) Mapper (WHAM) survey. She also showed that supernova explo-sions in the LMC sustain a large-scale emerging wind (0.4 M (cid:3692) yr –1 ). The level of ionisation in the Stream cannot be explained simply by photoionisation.The dust content and stellar feedback of the Magellanic Clouds were discussed by Margaret Meixner with a particular focus on the results obtained from projects based on infrared observations with the Spitzer and Herschel space telescopes. The LMC and SMC contain 7.3 x 10 M (cid:3692) (cid:64)(cid:77)(cid:67)(cid:3)(cid:23)(cid:13)(cid:18)(cid:3)(cid:151)(cid:3)(cid:16)(cid:15) M (cid:3692) of dust, respectively, accounted for by asymptotic giant branch stars, red supergiants and supernova production, as well as by dust growth by accretion. The LMC dust is predominantly made of amorphous silicates, while both amorphous silicates and carbon are 6 The Messenger 181 – Quarter 3 | 2020 present in equal amounts in the SMC. Future space missions like the James Webb Space Telescope will allow us to determine the compositon of the dust in the ejecta of supernova 1987A. Sikia Gautam studied the correlation between far-ultraviolet (associated with dust) and mid-infrared (associated with polycyclic aromatic hydrocarbon mole-cules) intensities in many diffuse locations in the SMC, concluding that ultraviolet (cid:68)(cid:76)(cid:72)(cid:82)(cid:82)(cid:72)(cid:78)(cid:77)(cid:3)(cid:78)(cid:81)(cid:72)(cid:70)(cid:72)(cid:77)(cid:64)(cid:83)(cid:68)(cid:82)(cid:3)(cid:72)(cid:77)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:72)(cid:77)(cid:83)(cid:68)(cid:81)(cid:82)(cid:83)(cid:68)(cid:75)(cid:75)(cid:64)(cid:81)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:3) rather than in the intervening medium along the line of sight. Pierre Maggi showed that dust is destroyed as a result of supernova explosions at a rate that (cid:67)(cid:68)(cid:79)(cid:68)(cid:77)(cid:67)(cid:82)(cid:3)(cid:78)(cid:77)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:82)(cid:79)(cid:68)(cid:66)(cid:72)(cid:106)(cid:66)(cid:3)(cid:68)(cid:75)(cid:68)(cid:76)(cid:68)(cid:77)(cid:83)(cid:25)(cid:3)(cid:72)(cid:83)(cid:3)(cid:72)(cid:82)(cid:3) higher for O and Fe and lower for Mg and Si. X-ray survey results also show that the higher numbers of core-collapse superno-vae compared to type I in the SMC, com-pared to the LMC, are perhaps related to their star formation history. Furthermore, supernovae in the LMC appear located in front of the disc (projected onto the bar) or behind it (belonging to 30 Doradus). By studying the spectral energy distribution of background galaxies (from u to K (cid:368)(cid:65)(cid:64)(cid:77)(cid:67)(cid:82)(cid:3) and with redshift < 6), Cameron Bell mapped the total instrinsic reddening of the SMC. This method successfully recovers high values in the centre and low values in the external regions utilising gal-axies with low levels of intrinsic reddening. Internal kinematics and dynamics of the Magellanic Clouds
Denis Erkal demonstrated that the mass of the LMC is large, ~ 10 M (cid:3692) , and because (cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3)(cid:72)(cid:83)(cid:3)(cid:76)(cid:84)(cid:82)(cid:83)(cid:3)(cid:71)(cid:64)(cid:85)(cid:68)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:67)(cid:3)(cid:83)(cid:81)(cid:64)(cid:66)(cid:68)(cid:81)(cid:82)(cid:3)(cid:78)(cid:69)(cid:3) the Milky Way structure. In particular, a better sky track, distance, proper motion and radial velocity for members of the Orphan stream are obtained when the LMC mass is taken into account. In addi-tion, velocity shifts of Milky Way satellites, warps of the Milky Way disc and a pull of the Milky Way mass internal to 30 kpc (cid:66)(cid:64)(cid:77)(cid:3)(cid:65)(cid:68)(cid:3)(cid:68)(cid:87)(cid:79)(cid:75)(cid:64)(cid:72)(cid:77)(cid:68)(cid:67)(cid:3)(cid:65)(cid:88)(cid:3)(cid:64)(cid:77)(cid:3)(cid:43)(cid:44)(cid:34)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:13)(cid:3) Gurtina Belsa argued that only a massive (cid:43)(cid:44)(cid:34)(cid:3)(cid:78)(cid:77)(cid:3)(cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:72)(cid:77)(cid:69)(cid:64)(cid:75)(cid:75)(cid:3)(cid:66)(cid:64)(cid:77)(cid:3)(cid:76)(cid:64)(cid:72)(cid:77)(cid:83)(cid:64)(cid:72)(cid:77)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:50)(cid:44)(cid:34)(cid:3) as a binary companion and survive a sta-ble disc after a recent (< 200 Myr) and direct (< 10 kpc) collision. This event is probably responsible for the formation of the one spiral arm and the offset of the disc from the bar in the LMC. At least 30% of Milky Way-type galaxies host an LMC-mass galaxy, with 70% having accreted at least one. Dwarf pairs around these hosts are however rare — they occur in only 6% of cases. Dana Casetti-Dinescu examined the ele-mental abundance and three-dimensional kinematics of OB-type stars in the periph- (cid:68)(cid:81)(cid:88)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:43)(cid:44)(cid:34)(cid:11)(cid:3)(cid:86)(cid:71)(cid:68)(cid:81)(cid:68)(cid:3)(cid:82)(cid:71)(cid:68)(cid:3)(cid:66)(cid:78)(cid:77)(cid:106)(cid:81)(cid:76)(cid:68)(cid:67)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3) some stars were born in situ. While the origin of similar stars in the Leading Arm is not clear, they could have formed (and may still be forming) in the LMC disc or in the Milky Way. Lara Cullinane explored the kinematics of the periphery of the LMC using data from the Magellanic Edges Survey (MagES) combined with Gaia. A feature in the northern disc of the LMC shows different kinematics from that of the disc, as obtained from a variety of disc rotation models. Scott Lucchini used hydrodynamical simulations in a tidal scenario to reproduce the Stream and Leading Arm gas. (cid:40)(cid:83)(cid:3)(cid:72)(cid:82)(cid:11)(cid:3)(cid:71)(cid:78)(cid:86)(cid:68)(cid:85)(cid:68)(cid:81)(cid:11)(cid:3)(cid:67)(cid:72)(cid:69)(cid:106)(cid:66)(cid:84)(cid:75)(cid:83)(cid:3)(cid:83)(cid:78)(cid:3)(cid:64)(cid:66)(cid:66)(cid:78)(cid:84)(cid:77)(cid:83)(cid:3)(cid:69)(cid:78)(cid:81)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3) gas mass in the Stream and the fragmen-tation of the Leading Arm at the same time. Preliminary simulations including the (cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:44)(cid:72)(cid:75)(cid:74)(cid:88)(cid:3)(cid:54)(cid:64)(cid:88)(cid:3)(cid:71)(cid:78)(cid:83)(cid:3)(cid:66)(cid:78)(cid:81)(cid:78)(cid:77)(cid:64)(cid:3) show a diffused Leading Arm made pre-dominantly of LMC material and some fragmentation in the trailing arm while matching the observations of the two LMC (cid:64)(cid:77)(cid:67)(cid:3)(cid:50)(cid:44)(cid:34)(cid:3)(cid:106)(cid:75)(cid:64)(cid:76)(cid:68)(cid:77)(cid:83)(cid:82)(cid:13)(cid:3)(cid:56)(cid:64)(cid:77)(cid:70)(cid:3)(cid:56)(cid:64)(cid:77)(cid:65)(cid:72)(cid:77)(cid:3)(cid:82)(cid:71)(cid:78)(cid:86)(cid:68)(cid:67)(cid:3) instead that a hydrodynamical simulation in a ram-pressure-plus-collision scenario is able to reproduce many properties of the Magellanic system, such as the den-sity of HI and the mass of ionised gas in the Stream with a 20% accuracy, the lead-ing arms, and the three-dimensional structure of young and old stars. Florian Niederhofer used data from the VMC survey to calculate the proper motion of young and old stars across the SMC. The median SMC motion and the velocity pat-tern across tiles are consistent with litera-ture determinations for both samples. Andres del Pino used Gaia data and a neural network method trained on the line-of-sight velocity of young, < 1 Gyr old, stars and on the distance of old RR Lyrae stars, and applied this to > 6 million stars with six-dimensional information, including age and metallicity, to study the distribution and kinematics of stellar popu- lations within the Magellanic Clouds. Their results reproduce two bridges (young and old) separated in distance by about 1.5 kpc, connecting extended distributions characterised by different kinematics.
The Magellanic Clouds as a distance scale anchor
Grzegorz Pietrzynski led us through the necessary steps to determine an accu-rate distance to the LMC using eclipsing binaries, one of the primary distance indi-cators in nearby galaxies, addressing the major sources of error in the calibration of the distance scale (population, extinction, zero-point, blending and physics of the indicator). Many years of extensive photo-metric and spectroscopic observations were invested to reach an accuracy of 1%. The role of the LMC in the distance scale was further discussed by Lucas Macri with respect to results on Cepheids and Mira stars, among the secondary dis-tance indicators. In particular, the combi-nation of sparse near-infrared observa-tions and highly sampled optical light curves, as well as single observations with the HST to overcome crowding, pro- (cid:85)(cid:72)(cid:67)(cid:68)(cid:82)(cid:3)(cid:64)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106)(cid:66)(cid:64)(cid:77)(cid:83)(cid:3)(cid:72)(cid:76)(cid:79)(cid:81)(cid:78)(cid:85)(cid:68)(cid:76)(cid:68)(cid:77)(cid:83)(cid:3)(cid:83)(cid:78)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3) period-luminosity relations used to derive distances, effectively reducing the uncer-tainty in the Hubble costant. Furthermore, a new periodogram technique based on (cid:64)(cid:3)(cid:76)(cid:84)(cid:75)(cid:83)(cid:72)(cid:12)(cid:65)(cid:64)(cid:77)(cid:67)(cid:3)(cid:76)(cid:78)(cid:67)(cid:68)(cid:75)(cid:3)(cid:83)(cid:78)(cid:3)(cid:106)(cid:83)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:75)(cid:72)(cid:70)(cid:71)(cid:83)(cid:3)(cid:66)(cid:84)(cid:81)(cid:85)(cid:68)(cid:82)(cid:3) will allow us to recover the period of many Mira stars beyond the LMC, to be detected in the future by the Synoptic Survey Telescope at Rubin Observatory. Anupam Bhardwaj showed that period- luminosity relations for Mira stars at maxi-mum light have a 30% less dispersion than at mean light. This is likely due to the destruction of unstable molecules when the Mira is at its warmest phase. Marek Gorski focused on the tip of red giant branch method to derive distances of systems at ~ 2 Mpc from ground-based and ~ 16 Mpc from space-based obser-vations. He highlighted recent improve-ments to the reddening, edge-detection method and to the near-infrared absolute magnitude calibration.The most accurate period-luminosity relations for Cepheids in the LMC and SMC, based on near-infrared photometry Astronomical News Cioni M.-R. L. et al., Report on the Workshop “A Synoptic View of the Magellanic Clouds”7
The Messenger 181 – Quarter 3 | 2020 from the VMC survey, were presented by Vincenzo Ripepi. However, the calibra-tion of these relations, which is based on Cepheids in the Milky Way and the cur- (cid:81)(cid:68)(cid:77)(cid:83)(cid:3)(cid:38)(cid:64)(cid:72)(cid:64)(cid:3)(cid:67)(cid:64)(cid:83)(cid:64)(cid:11)(cid:3)(cid:72)(cid:82)(cid:3)(cid:82)(cid:83)(cid:72)(cid:75)(cid:75)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:67)(cid:3)(cid:65)(cid:88)(cid:3)(cid:64)(cid:3) metallicity effect and parallax uncertain- (cid:83)(cid:72)(cid:68)(cid:82)(cid:13)(cid:3)(cid:51)(cid:71)(cid:68)(cid:82)(cid:68)(cid:3)(cid:72)(cid:82)(cid:82)(cid:84)(cid:68)(cid:82)(cid:3)(cid:86)(cid:72)(cid:75)(cid:75)(cid:3)(cid:76)(cid:78)(cid:82)(cid:83)(cid:3)(cid:75)(cid:72)(cid:74)(cid:68)(cid:75)(cid:88)(cid:3)(cid:65)(cid:68)(cid:3)(cid:106)(cid:87)(cid:68)(cid:67)(cid:3) in subsequent releases of the Gaia data. (cid:51)(cid:78)(cid:3)(cid:80)(cid:84)(cid:64)(cid:77)(cid:83)(cid:72)(cid:69)(cid:88)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:76)(cid:68)(cid:83)(cid:64)(cid:75)(cid:75)(cid:72)(cid:66)(cid:72)(cid:83)(cid:88)(cid:3) on the Cepheid period-luminosity rela-tions, Wolfgang Gieren showed an appli-cation of the infrared surface brightness technique to Milky Way, LMC and SMC sources. While the slopes of the relations (cid:64)(cid:81)(cid:68)(cid:3)(cid:77)(cid:78)(cid:83)(cid:3)(cid:72)(cid:77)(cid:107)(cid:84)(cid:68)(cid:77)(cid:66)(cid:68)(cid:67)(cid:3)(cid:65)(cid:88)(cid:3)(cid:76)(cid:68)(cid:83)(cid:64)(cid:75)(cid:75)(cid:72)(cid:66)(cid:72)(cid:83)(cid:88)(cid:11)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3) zero-points are — in the sense that more metal- poor Cepheids are fainter by (cid:108)(cid:15)(cid:13)(cid:17)(cid:18)(cid:3)(cid:10)(cid:14)(cid:108)(cid:3)(cid:15)(cid:13)(cid:15)(cid:21)(cid:3)(cid:76)(cid:64)(cid:70)(cid:14)(cid:67)(cid:68)(cid:87)(cid:13)(cid:3)(cid:33)(cid:78)(cid:70)(cid:84)(cid:76)(cid:72)(cid:143)(cid:3)(cid:47)(cid:72)(cid:75)(cid:68)(cid:66)(cid:74)(cid:72)(cid:3) explained that Cepheids in eclipsing binary systems allow us to derive physical parameters (for example, period, mass, and radius) from which to obtain evolution and pulsation models. These results place important constraints on, for example, the projection factor (the ratio between the pulsation velocity of the star and its radial motion), a crucial quantity for the calibra-tion of the infrared surface brightness technique. Roberto Molinaro showed the (cid:81)(cid:68)(cid:82)(cid:84)(cid:75)(cid:83)(cid:82)(cid:3)(cid:78)(cid:69)(cid:3)(cid:106)(cid:83)(cid:83)(cid:72)(cid:77)(cid:70)(cid:3)(cid:77)(cid:78)(cid:77)(cid:12)(cid:75)(cid:72)(cid:77)(cid:68)(cid:64)(cid:81)(cid:3)(cid:66)(cid:78)(cid:77)(cid:85)(cid:68)(cid:66)(cid:83)(cid:72)(cid:85)(cid:68)(cid:3) pulsation models to the light and radial velocity curves of a sample of Cepheids in both the LMC and the SMC. Extensive grids of models are built for each individ-ual star to derive structural parameters, distance and reddening, as well as to contruct period-luminosity and period- mass relations for comparison with those derived from observations.
Morphology and structure of the Magellanic Clouds from different stellar populations
Smitha Subramanian analysed data from the VMC survey and showed evidence for a population of red clump stars ~ 12 kpc in front of the SMC, emerging from a region ~ 2.5 kpc away from the centre and towards the east. This population was probably stripped during the last interac-tion episode with the LMC 300–400 Myr ago. Michele Cignoni presented data from the STEP (SMC in Time: Evolution of a Prototype interacting late-type galaxy) survey, where a bimodal red clump is also detected and where the bright com-ponent dominates the Magellanic Bridge. Furthermore, an analysis of blue-loop (core He burning) stars showed that star formation moved from the northeast of the SMC to the southwest; the age ranges in these regions span 120–200 Myr to 120–60 Myr, respectively, while both ranges are present in the central regions. (cid:35)(cid:64)(cid:75)(cid:64)(cid:75)(cid:3)(cid:36)(cid:75)(cid:3)(cid:56)(cid:78)(cid:84)(cid:82)(cid:82)(cid:78)(cid:84)(cid:106)(cid:3)(cid:84)(cid:82)(cid:68)(cid:67)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:53)(cid:44)(cid:34)(cid:3)(cid:82)(cid:84)(cid:81)(cid:85)(cid:68)(cid:88)(cid:3) data to explore the morphology of the Magellanic Clouds, creating maps with a spatial resolution of 0.13–0.16 kpc at dif-ferent ages. These maps demonstrate in great detail the history of interaction and evolution of the Magellanic Clouds. Anna Jacyszyn-Dobrzeniecka analysed data from the OGLE-IV survey to characterise the three-dimensional structure of the Magellanic Clouds. The clumpy appear-ance traced by Cepheids contrasts with the regular distribution traced by RR Lyrae stars in both galaxies. The spatial extension of old stars supports the pres-ence of two halos rather than a bridge connecting the LMC with the SMC. Massimiliano Gatto searched for stellar clusters in the outskirts of the LMC using deep photometric data obtained at the VLT Survey Telescope, from the YMCA (Yes, Magellanic Clouds Again) survey, and found 55 new candidates. Most of these clusters are of intermediate age (1–4 Gyr old) with a peak at 2 Gyr and only a few clusters in the age gap (4–10 Gyr).Doug Geisler showed that the metallicity distribution of stellar clusters in the SMC is bimodal, with peaks at about [Fe/H] = –0.8 and –1.1 dex, and does not show evidence (cid:78)(cid:69)(cid:3)(cid:64)(cid:3)(cid:82)(cid:83)(cid:81)(cid:78)(cid:77)(cid:70)(cid:3)(cid:70)(cid:81)(cid:64)(cid:67)(cid:72)(cid:68)(cid:77)(cid:83)(cid:11)(cid:3)(cid:86)(cid:71)(cid:72)(cid:75)(cid:68)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:3)(cid:81)(cid:68)(cid:67)(cid:3)(cid:70)(cid:72)(cid:64)(cid:77)(cid:83)(cid:3) branch stars have a unimodal distribution (peaked at [Fe/H] = –1.0 dex) and a nega-tive gradient that reverses to positive beyond 4 degrees from the centre of the galaxy. The age-metallicity relation of the (cid:66)(cid:75)(cid:84)(cid:82)(cid:83)(cid:68)(cid:81)(cid:82)(cid:3)(cid:82)(cid:71)(cid:78)(cid:86)(cid:82)(cid:3)(cid:64)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106)(cid:66)(cid:64)(cid:77)(cid:83)(cid:3)(cid:67)(cid:72)(cid:82)(cid:79)(cid:68)(cid:81)(cid:82)(cid:72)(cid:78)(cid:77)(cid:3) at all ages. In the presentation by Noelia Noël, supporting evidence was given for the disruption of the SMC: the gas appears decoupled from the stars, the kinematics of giant stars shows a lot of debris around a bound core and there are breaks in the low surface-brightness (cid:79)(cid:81)(cid:78)(cid:106)(cid:75)(cid:68)(cid:3)(cid:78)(cid:69)(cid:3)(cid:88)(cid:78)(cid:84)(cid:77)(cid:70)(cid:3)(cid:82)(cid:83)(cid:64)(cid:81)(cid:82)(cid:13)(cid:3)(cid:40)(cid:83)(cid:3)(cid:72)(cid:82)(cid:3)(cid:64)(cid:75)(cid:82)(cid:78)(cid:3)(cid:75)(cid:72)(cid:74)(cid:68)(cid:75)(cid:88)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3) the total mass of the SMC was much larger than the accepted value. Pushing to low surface brightnesses, Vasily Belokurov reviewed the recent studies of the detec-tion of ultra-faint satellites and their asso- ciation with the Magellanic system; cur-rently 7% of the Milky Way satellites could be brought in by the LMC. Satellites might also have been destroyed in the LMC group environment and this process most likely created stellar streams. In the LMC the southern arm appears as the counterpart of the north-ern arm, while there are many other ten-tacles that are possibly associated with episodes of earlier interactions between the Clouds. Further insight into the periphery of the Magellanic Clouds was given by Gary da Costa (on behalf of Dougal Mackey). Numerous structural distortions were found within the area covered by the MagES survey (~ 1200 square degrees around the LMC and ~ 200 square degrees around the SMC). The offset of several degrees between intermediate-age and old stars in the SMC might be related to an LMC-SMC encounter > 2 Gyr ago. Young stars in the Bridge form a chain of diffuse clusters in line with HI observa-tions, supporting a feedback process from supernovae and stellar winds. Camila (cid:45)(cid:64)(cid:85)(cid:64)(cid:81)(cid:81)(cid:68)(cid:83)(cid:68)(cid:3)(cid:66)(cid:78)(cid:77)(cid:106)(cid:81)(cid:76)(cid:68)(cid:67)(cid:11)(cid:3)(cid:84)(cid:82)(cid:72)(cid:77)(cid:70)(cid:3)(cid:82)(cid:79)(cid:68)(cid:66)(cid:83)(cid:81)(cid:78)(cid:82)(cid:66)(cid:78)(cid:79)(cid:72)(cid:66)(cid:3) observations of individual stars, that two of the streams previously detected from the distribution of blue horizontal branch stars are indeed kinematically coherent structures. On the other hand, the Pisces (cid:78)(cid:85)(cid:68)(cid:81)(cid:67)(cid:68)(cid:77)(cid:82)(cid:72)(cid:83)(cid:88)(cid:3)(cid:72)(cid:82)(cid:3)(cid:67)(cid:72)(cid:69)(cid:106)(cid:66)(cid:84)(cid:75)(cid:83)(cid:3)(cid:83)(cid:78)(cid:3)(cid:64)(cid:82)(cid:82)(cid:78)(cid:66)(cid:72)(cid:64)(cid:83)(cid:68)(cid:3)(cid:86)(cid:72)(cid:83)(cid:71)(cid:3)
Magellanic debris, but may be consistent with the expected Magellanic wake into the Galactic halo. The discovery of a young cluster, associated with the Leading Arm because of its distance, metallicity and radial velocity, was presented by Adrian Price-Whelan. This cluster was found from a search of co-moving blue horizontal branch stars and subsequent follow-up studies; it might have formed as a result of the interaction between the Leading Arm and the Milky Way gas.
Ongoing and future surveys of the Magellanic Clouds
David Niedever opened the last session by presenting results from two surveys: the Survey of the Magellanic Stellar History (SMASH) and the Magellanic Clouds sur-vey using the Apache Point Observatory Galactic Evolution Experiment (APOGEE). 8
The Messenger 181 – Quarter 3 | 2020
Their combination will set constraints on the evolution of the galaxies. In particular, deep photometry was used to derive a three-dimensional map of the LMC, to detect a warp and a stellar ring in its disc, and to probe the stellar periphery to 21 degrees from the centre. Extensive spectroscopy was used to derive the (low) (cid:82)(cid:83)(cid:64)(cid:81)(cid:3)(cid:69)(cid:78)(cid:81)(cid:76)(cid:64)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:68)(cid:69)(cid:106)(cid:66)(cid:72)(cid:68)(cid:77)(cid:66)(cid:88)(cid:3)(cid:66)(cid:78)(cid:76)(cid:79)(cid:64)(cid:81)(cid:68)(cid:67)(cid:3)(cid:83)(cid:78)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3) of the Milky Way — supporting their for-mation in low-density environments and a (cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:72)(cid:77)(cid:69)(cid:64)(cid:75)(cid:75)(cid:3)(cid:82)(cid:66)(cid:68)(cid:77)(cid:64)(cid:81)(cid:72)(cid:78)(cid:13)(cid:3)(cid:33)(cid:81)(cid:84)(cid:77)(cid:78)(cid:3)(cid:35)(cid:72)(cid:64)(cid:82)(cid:3)(cid:72)(cid:77)(cid:83)(cid:81)(cid:78)(cid:12) duced the VIsible Soar photometry of star Clusters in tApii and Coxi HuguA (VISCACHA) survey aimed at the study of stellar clusters in the Magellanic Clouds. The spatial resolution of this survey is better than that achieved by other ground-based photometric surveys because of the use of adaptive optics, which should improve the derivation of the physical properties of stellar clusters (age, mass, reddening, distance, and structural parameters) from the interpre-tation of colour-magnitude diagrams. Maria-Rosa Cioni focused on two surveys using the VISTA telescope: the recently completed near-infrared photometric sur-vey VMC and the planned spectroscopic 1001MC (One Thousand and One (cid:44)(cid:64)(cid:70)(cid:68)(cid:75)(cid:75)(cid:64)(cid:77)(cid:72)(cid:66)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:82)(cid:8)(cid:3)(cid:82)(cid:84)(cid:81)(cid:85)(cid:68)(cid:88)(cid:13)(cid:3)(cid:39)(cid:72)(cid:70)(cid:71)(cid:75)(cid:72)(cid:70)(cid:71)(cid:83)(cid:82)(cid:3)(cid:69)(cid:81)(cid:78)(cid:76)(cid:3) the VMC include: the spatial variation of the distribution of mass in the SMC, developing an elongated shape between 5 and 3 Gyr ago, truncated to the west between 500 and 200 Myr ago; the domi-nant number of 100 Myr-old Cepheids in the northwest of the SMC at closer dis-tances compared to the majority of 200 (cid:44)(cid:88)(cid:81)(cid:12)(cid:78)(cid:75)(cid:67)(cid:3)(cid:78)(cid:77)(cid:68)(cid:82)(cid:3)(cid:72)(cid:77)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:66)(cid:68)(cid:77)(cid:83)(cid:81)(cid:68)(cid:26)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:82)(cid:72)(cid:70)(cid:77)(cid:72)(cid:106) -cant distance modulus variation across the LMC and SMC obtained from the tip of the red giant branch method. The sci- (cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:70)(cid:78)(cid:64)(cid:75)(cid:82)(cid:11)(cid:3)(cid:64)(cid:81)(cid:68)(cid:64)(cid:11)(cid:3)(cid:83)(cid:88)(cid:79)(cid:68)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:77)(cid:84)(cid:76)(cid:65)(cid:68)(cid:81)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:64)(cid:81) -gets (about 0.5 million stars and 0.1 million background galaxies) that the 1001MC plans to observe, as part of the consor-tium that develops the 4-metre Multi- Object Spectroscopic Telescope (4MOST), were also presented. First results from the Galactic ASKAP (Australian Square (cid:42)(cid:72)(cid:75)(cid:78)(cid:76)(cid:68)(cid:83)(cid:68)(cid:81)(cid:3)(cid:32)(cid:81)(cid:81)(cid:64)(cid:88)(cid:3)(cid:47)(cid:64)(cid:83)(cid:71)(cid:106)(cid:77)(cid:67)(cid:68)(cid:81)(cid:8)(cid:3)(cid:82)(cid:84)(cid:81)(cid:85)(cid:68)(cid:88)(cid:11)(cid:3) including the Magellanic Clouds and Bridge, were shown by Nickolas Pingel. (cid:40)(cid:77)(cid:3)(cid:79)(cid:64)(cid:81)(cid:83)(cid:72)(cid:66)(cid:84)(cid:75)(cid:64)(cid:81)(cid:11)(cid:3)(cid:71)(cid:68)(cid:3)(cid:81)(cid:68)(cid:79)(cid:78)(cid:81)(cid:83)(cid:68)(cid:67)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:67)(cid:68)(cid:83)(cid:68)(cid:66) -tion of a break in the power spectrum of HI, demonstrating that this high spatial and spectral resolution survey will allow us to characterise turbulence (and kine-matics) to an unprecedented level. A cata-logue of OH masers will also be provided. In the X-ray domain, Frank Haberl re-viewed the status of population studies from the XMM-Newton surveys of the Magellanic Clouds and elaborated on fu-ture prospects using the eROSITA instru-ment on board the Spectrum- Roentgen-Gamma satellite. In particular, he high- lighted studies of a large sample (~ 120) of high-mass (Be) X-ray binaries in the SMC, correlated with star formation at 25–60 Myr, where only half of them are pulsars. The expected exposure time of eROSITA across the Magellanic Clouds during the course of the survey, details about the instruments, its performance, (cid:64)(cid:77)(cid:67)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:106)(cid:81)(cid:82)(cid:83)(cid:3)(cid:75)(cid:72)(cid:70)(cid:71)(cid:83)(cid:3)(cid:66)(cid:78)(cid:76)(cid:76)(cid:72)(cid:82)(cid:82)(cid:72)(cid:78)(cid:77)(cid:72)(cid:77)(cid:70)(cid:3)(cid:72)(cid:76)(cid:64)(cid:70)(cid:68)(cid:3) were also presented. To conclude this session, Knut Olsen presented the Rubin Observatory Legacy Survey of Space and Time (LSST) which is due to begin in 2023 at Vera C. Rubin Observatory. The pro-posed science case for observing the Magellanic Clouds makes use of the three main advantages of the telescope: i.e., wide, fast and deep. It addresses a broad range of questions that encompass most of the topics discussed in the meeting so far. It also faces technical challenges, such as solving the problem of separating stars (cid:69)(cid:81)(cid:78)(cid:76)(cid:3)(cid:70)(cid:64)(cid:75)(cid:64)(cid:87)(cid:72)(cid:68)(cid:82)(cid:3)(cid:72)(cid:77)(cid:3)(cid:67)(cid:68)(cid:77)(cid:82)(cid:68)(cid:3)(cid:82)(cid:83)(cid:68)(cid:75)(cid:75)(cid:64)(cid:81)(cid:3)(cid:106)(cid:68)(cid:75)(cid:67)(cid:82)(cid:11)(cid:3)(cid:68)(cid:87) -tracting photometry for objects in these (cid:106)(cid:68)(cid:75)(cid:67)(cid:82)(cid:11)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:67)(cid:68)(cid:106)(cid:77)(cid:72)(cid:77)(cid:70)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:69)(cid:78)(cid:78)(cid:83)(cid:79)(cid:81)(cid:72)(cid:77)(cid:83)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3) cadence of a multitude of repeated observations.
Main conclusions and ways forward
The workshop was a great success. It provided a crucial platform for the pres-entation of a state-of-the-art view of the Magellanic system, comparing and com-bining results from different teams and projects, and stimulating a discussion that brought us to a better understanding of our neighbouring galaxies and their role as important suppliers of material to the Milky Way halo, demonstrating and quantifying the processes related to gal-axy interactions, as well as group accre-tion in general that may be applicable to more distant systems. The workshop enhanced the impact of the VMC ESO Public Survey in the context of other ded-icated and complementary programmes, for example using CTIO telescopes, and the plans formulated for future consor-tium observations of the Magellanic Clouds using the Multi Object Optical and Near-infrared Spectrograph (MOONS) and 4MOST instruments (see, for exam-ple, Cioni et al., 2019).
Demographics
The 104 participants at the workshop came from 17 different countries. The majority were from the United States of America and Germany, with 20% each, followed by ESO, Italy, Australia and the United Kindgom with 10% each; about 60% of the participants were from ESO Member States. Of the attendees, 35% were female and the Science Organising (cid:34)(cid:78)(cid:76)(cid:76)(cid:72)(cid:83)(cid:83)(cid:68)(cid:68)(cid:3)(cid:69)(cid:78)(cid:81)(cid:76)(cid:84)(cid:75)(cid:64)(cid:83)(cid:68)(cid:67)(cid:3)(cid:64)(cid:3)(cid:82)(cid:66)(cid:72)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:79)(cid:81)(cid:78) - (cid:70)(cid:81)(cid:64)(cid:76)(cid:76)(cid:68)(cid:3)(cid:83)(cid:71)(cid:64)(cid:83)(cid:3)(cid:81)(cid:68)(cid:107)(cid:68)(cid:66)(cid:83)(cid:68)(cid:67)(cid:3)(cid:83)(cid:71)(cid:72)(cid:82)(cid:3)(cid:79)(cid:68)(cid:81)(cid:66)(cid:68)(cid:77)(cid:83)(cid:64)(cid:70)(cid:68)(cid:13)(cid:3) The selection of contributed talks was made without considering the gender of the applicants while invited talks were selected to include, where possible, female speakers. It is interesting to note that the percentage of female partici-pants matched the percentage of females who delivered review presentations. In addition, the workshop had a good bal-ance of career level and seniority. Each of the eight workshop sessions had three review talks and two talks from students.
Acknowledgements
A big thank you goes to many people: the other (cid:76)(cid:68)(cid:76)(cid:65)(cid:68)(cid:81)(cid:82)(cid:3)(cid:78)(cid:69)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:50)(cid:66)(cid:72)(cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:46)(cid:81)(cid:70)(cid:64)(cid:77)(cid:72)(cid:82)(cid:72)(cid:77)(cid:70)(cid:3)(cid:34)(cid:78)(cid:76)(cid:76)(cid:72)(cid:83)(cid:83)(cid:68)(cid:68)(cid:3)(cid:134)(cid:3)
Kenji Bekki, Andrew Cole, Elena D’Onghia, Eva Grebel, Vanessa Hill, Rolf-Peter Kudritzki, Jacco van (cid:43)(cid:78)(cid:78)(cid:77)(cid:11)(cid:3)(cid:45)(cid:64)(cid:78)(cid:76)(cid:72)(cid:3)(cid:44)(cid:66)(cid:34)(cid:75)(cid:84)(cid:81)(cid:68)(cid:12)(cid:38)(cid:81)(cid:72)(cid:69)(cid:106)(cid:83)(cid:71)(cid:82)(cid:11)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:40)(cid:70)(cid:78)(cid:81)(cid:3)(cid:50)(cid:78)(cid:82)(cid:89)(cid:88)(cid:77)(cid:82)(cid:74)(cid:72)(cid:3)(cid:134)(cid:3) for their valuable help in preparing an excellent sci- (cid:68)(cid:77)(cid:83)(cid:72)(cid:106)(cid:66)(cid:3)(cid:79)(cid:81)(cid:78)(cid:70)(cid:81)(cid:64)(cid:76)(cid:76)(cid:68)(cid:26)(cid:3)(cid:83)(cid:71)(cid:68)(cid:3)(cid:36)(cid:50)(cid:46)(cid:3)(cid:75)(cid:78)(cid:70)(cid:72)(cid:82)(cid:83)(cid:72)(cid:66)(cid:82)(cid:3)(cid:64)(cid:77)(cid:67)(cid:3)(cid:66)(cid:64)(cid:83)(cid:68)(cid:81)(cid:72)(cid:77)(cid:70)(cid:3)(cid:69)(cid:78)(cid:81)(cid:3) a smooth and enjoyable experience; the local organ-iser committee members, Lisa Löbling and Sara Mancino; and, in particular, Stella Chasiotis- Klingner for her effective and swift management of the meet- (cid:72)(cid:77)(cid:70)(cid:13)(cid:3)(cid:51)(cid:71)(cid:68)(cid:3)(cid:106)(cid:77)(cid:64)(cid:77)(cid:66)(cid:72)(cid:64)(cid:75)(cid:3)(cid:66)(cid:78)(cid:77)(cid:83)(cid:81)(cid:72)(cid:65)(cid:84)(cid:83)(cid:72)(cid:78)(cid:77)(cid:3)(cid:69)(cid:81)(cid:78)(cid:76)(cid:3)(cid:36)(cid:50)(cid:46)(cid:3)(cid:86)(cid:64)(cid:82)(cid:3)(cid:64)(cid:75)(cid:82)(cid:78)(cid:3) instrumental in facilitating the participation of early career scientists.
References
Cioni, M.-R. L. et al. 2019, The Messenger, 175, 55
Links