Nuclear star clusters (NSCs) are found in at least 60% of galaxies, but their formation path is still unclear. NSCs could form from infalling gas at the galactic centre or might build up from in-spiraling globular clusters (GCs). In the first scenario, the NSC should show high angular momentum and higher metallicities from subsequent star bursts while in the second scenario, the NSC should reflect the low angular momentum and low metallicities of the surroundingGC population. To constrain these scenarios, we use observations taken with the Multi Unit Spectroscopic Explorer (MUSE) of three early-type galaxies in the Fornax galaxy cluster to study the kinematic and stellar population properties of their GC systems.I will present my current work on the kinematic analysis of the three galaxies by comparing the integrated light to GCs and planetary nebulae as point source tracers.

In order to understand the nature of dark matter, reliable and comprehensive dynamical studies of dark matter dominated galaxies are of utmost importance. Local dwarf spheroidal (dSph) galaxies are the perfect objects for those kind of studies. So far, most approaches have assumed spherical symmetry on their dynamical models; however, we know that the stellar component of these galaxies is not spherical. Assuming spherical symmetry might produce a bias in their mass measurements. Here we present a generalisation, utilising axisymmetric Jeans equations, in order to model their internal dynamics and velocity dispersion profiles. This approach allows us to determine the mass distribution of the underlying axisymmetric stellar system in general, and apply it into dSph galaxies. Utilising mock catalogs, we have analysed the parameter space of the dark matter halo model. If only line-of-sight velocities are used, the halo parameters show a significant degeneracy, which is strongest between the meridional anisotropy and the axis ratio of the halo. This degeneracy cannot be broken with line-of-sight velocities alone, even if the sample size is increased or if the analysis is done utilising a discrete approach rather than the usual binning of the data. We have applied our axisymmetric Jeans models to the Local Group dSph galaxies Fornax and Sculptor, the ones with the largest datasets available in the literature, and conclude that even if this degeneracy limits our constraints on the shape of the dark matter halo, the mass within the half-light radius is still a robust result.

Galaxy groups are believed to be important sites of gas pre-processing in galaxies, which in turn impacts their stellar and morphological evolution.  As groups accrete more galaxies, the groups themselves become increasingly poor in neutral atomic hydrogen (HI), and more cluster-like.  Studies of compact groups suggest that gas processing through tidal interactions simultaneously depletes the cold gas in galaxies and contributes to the build-up of the warm-hot intragroup medium that is sometimes detected in X-rays.  We present the results of stacking ROSAT All-Sky Survey images for a large sample of groups for which we have simultaneous HI data from the ALFALFA survey in an attempt to detect the build-up of the WHIM in intermediate mass groups M>10^13 M_Sun, where we begin to see the impact of the group environment on the HI content of their member galaxies.  With HI and X-ray observations together, the goal is to simultaneously trace the recent accretion of galaxies and groups, and build-up of the hot gas reservoirs in groups and clusters.

The physical processes leading to the conversion of gas to stars can be best understood through direct observations of cold atomic and molecular gas, which act as the reservoir for star formation. Considerable progress has been made in mapping the distribution of diffuse gas in the circumgalactic medium of galaxies using absorption from Lyman-alpha and metal lines like Mg II. However, the distribution of high neutral hydrogen column density (N(HI) >~ 10^19 cm^-2) cold (T ~ few 100 K) gas around galaxies is not yet well understood. Such cold gas can be traced via HI 21-cm absorption without being affected by dust and luminosity biases. Hence, with a view to map the distribution of cold HI gas around galaxies, we have carried out systematic surveys of HI 21-cm absorption at both low (z < 0.4) and high (0.5 < z < 1.5) redshifts, using quasar-galaxy-pairs and strong Mg II/ Fe II systems, respectively. The main results from our studies will be presented in this talk.

The dynamical scaling relations of galaxies -- connecting their luminosity and velocity profiles -- have long been an important source of information about galaxy formation. In this talk I will present a detailed statistical study of four such scalings -- the Tully-Fisher, Faber-Jackson, mass discrepancy-acceleration relations, and Fundamental Plane -- with the aim of inferring the galaxy-halo connection and assessing the validity of current empirical models.

I will demonstrate that the relations provide evidence for correlations of galaxy size and morphology with halo properties at fixed stellar mass, and constrain the scatter of the galaxy-halo connection and the impact of galaxy formation on halo profiles. Finally, I quantify various discrepancies between the data and model predictions, most notably in the relations' intrinsic scatter.

Radio-loud AGN (RLAGN) tend to reside in the most massive dark matter halos, and have a long history of being used to efficiently identify rich, high-redshift structures (i.e., clusters and protoclusters). Our team contributed to this effort with a targeted 400hr Spitzer program surveying 420 RLAGN (radio-loud quasars and high-z radio galaxies) at 1.3 < z < 3.2 across the full sky: Clusters Around RLAGN (CARLA; Wylezalek et al., 2013, 2014). The CARLA Survey identified 200 cluster candidates at 1.3 < z < 3.2 as 2-8 sigma overdensities of red color-selected Spitzer/IRAC galaxies around the targeted powerful RLAGN. I will present results from our follow-up 40-orbit HST program on the 20 densest CARLA cluster candidates at 1.4 < z < 2.8. We spectroscopically confirm 16/20 distant structures associated with the RLAGN, up to z=2.8 (Noirot et al., 2016, 2017). For the first time at these redshifts, we statistically investigate the star-formation content of a large sample of galaxies in dense structures. We find that massive galaxies are located below their star-forming main-sequence up to z=2. This implies that the massive star-forming end of the (proto)cluster population already followed an accelerated evolution at these high redshifts. We also find an increasing concentration of star-forming members with smaller radii relative to the RLAGN, consistent with a reversal of the SFR-density relation.

I will show that our confirmed CARLA structures represent rich environments comprised of mixed populations, including both evolved, passive, massive galaxies, and galaxies with ongoing star formation. Together, this unprecedented sample of 16 confirmed structures at 1.4 < z < 2.8 constitutes an ideal sample for further statistical investigation of the cluster transition phase, including study of quenching mechanisms

I will discuss our recent results studying light curves of hydrogen-rich supernovae during the first few days after explosion. The first days of emission encode important information about the physical system, and it is possible to relate the early-time light curve to the radius of the progenitor star by using shock-cooling models. I will show the first systematic application of these models to data from the Palomar Transient Factory (PTF). I will also discuss improved observing strategies to obtain more constraining results in the future. One important question is the effect of circumstellar material on the light curves, motivating future systematic spectroscopic sequencing of these events.

To this end, we have designed a new medium resolution UV-VIS spectrograph. The Multi-Imaging Transient Spectrograph (MITS) is the R~4500 UV-VIS arm of the Son Of X-Shooter (SOXS) spectrograph proposed for ESO’s 3.6 m New Technology Telescope. Our design divides the spectrum into several channels, allowing optimization for each narrow part of the spectrum. We estimate a 50-100% improvement in throughput relative to a classical 4-C echelle design. Our design has passed a preliminary design review and is expected on the telescope in 2021.

Throughout history, the light from stellar populations has been the dominant way we determine the properties of galaxies. The stellar initial mass function (IMF) parameterises the number of stars formed as a function of their mass, and is commonly assumed to have a universal form regardless of the star forming environment. Recently the universality of the IMF has become a hotly debated topic in astrophysics, as evidence for the detections of real variations are becoming substantial. In this work, I present constraints on the high mass slope (m∗ > 1M⊙) of the IMF using Hubble Space Telescope (HST) observations of three nearby dwarf irregular galaxies that are resolved into individual stars. My approach compares observed Hα flux and the luminosity distribution  of main sequence stars  to the expectations from simulated populations with varying IMFs. Where possible, the two methods are  combined to derive tighter constraints. Finally, I determine the local Kennicutt-Schmidt star formation law to quantify how star formation and the IMF are correlated.

Gravitational collapse during the Universe's first billion years transformed a nearly homogeneous matter distribution into a network of filaments - the Cosmic Web - where galaxies form and evolve. Because most of this material is too diffuse to form stars, its study has been limited so far to absorption probes against background sources. In this talk, I will present the results of a new program to directly detect and study high-redshift cosmic gas in emission using bright quasars and galaxies as external "sources of illumination’’. In particular, I will show results from ultra-deep narrow-band imaging and recent integral-field-spectroscopy as a part of the MUSE Guaranteed Time of Observation program that revealed numerous giant Lyman-alpha emitting filaments extending up to several hundred kpc around quasars and bright galaxies. I will discuss how the unexpectedly high luminosities of these systems, together with the constraints from Helium and metal extended emission, represent a challenge for our current understanding of cosmological structure formation. In particular, I will show that current observations suggest that a large amount of “cold" and dense gaseous “clumps" should be present around high-redshift galaxies and I will present our first attempts to understand the origin and nature of these structures using high-resolution hydrodynamical simulations.

Bars are common in the local Universe, approximately ⅓ of the nearby disc galaxies host strong bars. However, the role of bars in the evolution of their host galaxies is still uncertain. I will present the results of a multi-component (disc+bar and disc+bar+bulge) and multi-wavelength (SDSS ugriz) image decomposition on what is currently the largest sample of local galaxies with strong bars (~3,500 barred SDSS galaxies), selected using Galaxy Zoo morphologies. Measuring the properties of these galaxies reveals differences in the colours of the components of the barred galaxies and a similar mass-matched sample of galaxies without bars, suggesting that bars can lead to the quenching of star formation by driving gas to the galaxy centres, as shown by some simulations.

I will also show a curious sample of low mass galaxies with a bar that is offset from the disc, which I identified in the sample of barred galaxies (Kruk et al. 2017). It is hypothesised that these offsets arise in galaxy interactions, but a nearest neighbour search does not produce a correlation between the offsets and companions. I will also discuss alternative scenarios that can give rise to the offsets.

Finally, I will show the new Zooniverse Project Builder, that allows anyone to build their own citizen science project in just a few minutes!

Jellyfish galaxies are objects exhibiting disturbed morphology, mostly in the form of tails of gas stripped
from the main body of the galaxy. We have undertaken the first systematical investigation of this
phenomenon in a sample of ~100 cluster galaxies selected because of they disturbed morphologies in B-
band images. MUSE data have been so far obtained for most of the sample. In this talk I will briefly present
the details of the survey and some of its preliminary results.

In this talk, I will present the first detection of laser-induced Raman (in addition to Rayleigh and Mie) scattering above Cerro Paranal with the MUSE integral field unit. This additional source of (non-elastic) scattering for the photons from the 4LGSF lasers (and the PARLA laser too) gives rise to a very specific set of emission lines that can contaminate certain observations at visible wavelengths. Beyond the physical description of the phenomena and the characterisation of its spectral signature, I will discuss some of the direct consequences of this effect for operations.

Despite several years of studies, the chemical evolution history of the Large Magellanic Cloud (LMC), as well as its star formation history, is still poorly understood. Three main stellar populations have been identified in the LMC: (a) an old population, coeval to the Galactic Halo, (b) an intermediate-age population (1-3 Gyr) that is the dominant one, and (c) a young component related to the most recent bursts of star formation.  The studies available so far based on high-resolution spectroscopy provide mainly information about the chemical composition of the young/intermediate-age populations, while only a few studies on old LMC globular clusters provide information about the chemistry in the oldest stars of LMC.

In this talk I will present the first homogeneous metallicity scale of old LMC clusters obtained using high-resolution spectroscopy, discussing the differences in the main groups of elements between old LMC and Milky Way clusters.

Currently, the Baade-Wesselink (BW) method is able to determine the
distances to individual classical Cepheids with an uncertainty
of 7-10 percent. In my talk I will describe our efforts to reduce
the systematic uncertainty of the method down to an expected 2-3%,
mainly by improving our knowledge about the p-factors of Cepheids
which are needed to transform the observed radial velocity curves
to the Cepheid pulsational velocity curves. The current uncertainty
on the p-factors dominates the systematic error on BW distances.

Galaxy clusters are known to host a variety of diffuse and extended
radio sources, including tailed radio galaxies, radio bubbles filling
holes in the ICM distribution, diffuse giant radio sources revealing
the presence of relativistic electrons and magnetic fields in the
intra-cluster volume. It is currently matter of debate how the
non-thermal components that we observe at radio wavelengths affect the
evolutionary physics of galaxy clusters. In this talk, I will give an
overview of the expected impact of Square Kilometre Array (SKA)
observations on non-thermal cluster studies.

Being much brighter than red giant stars, globular clusters allow old stellar populations of galaxies to be studied spectroscopically to much greater distances. Using data from the WAGGS survey of massive star clusters in the Milky Way and its satellite galaxies and the SLUGGS survey of the globular cluster systems of massive early-type galaxies, I will talk about how we can measure the metallicities of globular clusters using the strength of the calcium triplet in integrated light. Using globular cluster metallicity distributions and the relationships between globular cluster colour and metallicity, I will present evidence that different galaxies with similar masses experienced different formation histories. I will compare these observations with the predictions of the E-MOSAICS simulations of the formation of globular cluster systems.

Extreme kinematics in the white dwarf population might imply old age
and halo membership for some of its members, although in a few cases
more unusual pathways are implicated. Spectral analyses of high-
proper motion white dwarfs deliver stellar parameters from which we
obtain a photometric distance and surface abundances from which
we collect some clues of past interaction and binary ejection.
I will summarize past and present work, including our own, aimed
at identifying possible halo white dwarfs that are used to estimate
the age the Milky Way. I will also describe a few extreme objects
with unusual hyper-velocity trajectories. Distance measurements
are the most challenging aspect of this work and, as we all often say,
Gaia should help sort this one out.

The mass loss from evolved stars plays a number of key roles in stellar and galactic evolution. As well as being the main source of dust and chemically-enriched material for the ISM, mass-loss is crucial to understanding the final fates of stars. At the high-mass end, mass-loss is the key parameter that determines when a given star will explode as a supernova, and what kind of supernova it will become. Meanwhile for low- and intermediate-mass stars, mass loss on the asymptotic giant branch (AGB) allows them to avoid this fate. I will present some recent developments in understanding the mass loss of AGB and red supergiant stars, along with some open challenges and new projects aiming to solve them.

The observational properties of a special class of stars (the so-called Blue Straggler stars – BSS) in Globular Clusters are discussed in the framework of using this stellar population as probe of the dynamical processes occurring in these high-density stellar systems. In particular, the shape of the BSS radial distribution and their level of central segregation have been found to be powerful tracers of the level of the dynamical evolution of the hosting cluster, thus allowing the definition of an empirical 'dynamical clock'.

VESTIGE (A Virgo Environmental Survey Tracing Ionised Gas Emission) is a deep
blind Halpha narrow-band imaging survey of the Virgo cluster within its virial
radius (~ 104 deg.sq.). VESTIGE is a CFHT large program that will be carried
out with MegaCam in 2017-2019 (50 alloctaed nights). I will introduce the
survey describing its technical aspects and its scientific objectives, and
present the first results obtained after the analysis of some pilot observations
of a few representative Virgo cluster galaxies. The data obtained so far suggest
that the observation of the ionised gas emission at very low surface brightness
levels is to date one of the most powerful tools to study ongoing perturbations
in rich environments.

The cold phase of the interstellar medium has a central role in galaxy growth and evolution. In normal galaxies following the so-called “main sequence” of star-forming galaxies, the star formation rate is believed to be regulated uniquely by the amount of gas available, and more specifically by the mass of cold and dense molecular gas. Despite the enormous efforts to trace molecular gas in larger and larger samples of galaxies, at multiple scales and at multiple epochs, nearly all of our empirical knowledge of scaling relations linking molecular gas and galaxy properties is still based on observations of massive (e.g. M*>10^10 M_Sun), metal-rich and gas-rich spirals. There is therefore a strong motivation to test molecular gas scaling relations over a much broader dynamic range of galaxy properties. With this goal in mind, we have undertaken the “APEX low-redshift legacy survey of molecular gas (ALLSMOG)”, an ESO large programme to survey the CO(2-1) line emission in a sample of ~100 normal star forming galaxies in the local Universe, characterised by stellar masses (10^8.5<M*[M_Sun]<10^10), SFRs and gas-phase metallicities significantly lower than have been probed by previous CO observations. The reduced spectra have been recently released through the ESO Phase 3 platform. I will present our latest results based on the full ALLSMOG dataset.

Dwarf galaxies are tracers of the fine-structure of the large-scale structure of the universe. In my talk I will present our recent dwarf galaxy surveys in the nearby Centaurus Group (Dark Energy Camera) and the M101 group complex (SDSS). Two planes of satellites around CenA were recently discovered, which provide a unique opportunity to test cosmological predictions beyond the Local Group. We find evidence that these satellite planes are corotating, posing a major challenge to Lamda+CDM. The implications of our findings for the standard model of cosmology and alternative models are critically discussed.

The SkyMapper Southern Survey is now approaching its first large data release, covering nearly all of the Southern hemisphere in six optical bands. This talk will cover all aspects of the project, from its history and operations to the science currently pursued. This includes searching for metal-poor stars in the Milky Way and bright quasars at high redshift as well as mapping temporal variations of star formation in nearby galaxies. SkyMapper also operates a transient survey to supply the local anchoring for SN Ia cosmology, and engages in optical follow-up of fast radio bursts and neutron star mergers. Public awareness for SkyMapper benefits from our Hunt for Planet Nine as broadcast by BBC Stargazing Live.

I will describe the shape of the bar and bulge of the inner Galaxy traced using red clump stars in VVV and UKIDSS as standard candles. These demonstrate that the Milky Way has a 5kpc bar whose central ~2kpc is the boxy/peanut bulge. This is significantly longer than previous estimates and thus limits the rotation speed of the bar since corotation must lie beyond 5kpc, making the bar longer and slower than previously thought.

This shape, together with a wealth of kinematic data on individual bulge stars, has been included in made-to-measure models of the inner Galaxy to produce dynamical models of the whole bar and bulge. The models have wide applicability and we have used them together with microlensing data to determinate that the IMF in inner Galaxy is indistinguishable from the local IMF despite the very different timescale and redshift of star formation.

The dynamical models place corotation at 6.1kpc, and they naturally reproduce the dynamics of the well known Hercules stream in the solar neighbourhood. A longer 5kpc bar and central bulge, rotating so that corotation lies at 6.1kpc, is therefore a consistent description that can be further tested with data from VVVX and GAIA DR2 next year.

I will present numerical models of the gas dynamics in the inner parsec of the Galactic centre. We follow the gas from its origin as stellar winds of around 30 observed young massive stars, until it is either captured by the central black hole, or leaves the region.  I will show how comparing the simulations with recent Chandra observations confirms the origin of the gas in stellar winds, and constrains the properties of Sgr A* outflows during the last few hundred years.

Due to their steep spectra, low-frequency observations of FR II radio galaxies potentially provide key insights in to the morphology, energetics and underlying physics of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored.

In this talk, I present the latest results from the nearby-AGN KSP using LOFAR and the VLA at frequencies between 50 and 460 MHz to investigate the dynamics, energetics and particle acceleration in FR II radio galaxies. For the first time, this allows us to undertake well resolved, detailed studies of FR IIs at low frequencies and place tight constraints on the low-energy electron distribution, magnetic field strength, and total energy content of the lobes. I discuss the impact this has on our understanding of nearby FR II radio galaxies and how an improved knowledge of their spectral structure on small spatial scales advances our understanding of the mechanisms which drive these powerful radio sources.

I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are arguably its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the inspiral and merger of a binary system of neutron stars is more than a strong source of gravitational waves. Indeed, while the gravitational signal can provide tight constraints on the equation of state for matter at nuclear densities, the formation of a black-hole--torus system can explain much of the phenomenology of short gamma-ray bursts, while the the ejection of matter during the merger can shed light on the chemical enrichment of the universe.

Circumgalactic medium (CGM), the interface between the interstellar medium and the intergalactic medium (IGM), is a complicated site of entwined gas from the IGM accretion and galactic outflows. QSO absorption line systems are amongst the best places to study the physical properties of the CGM. MUSE observations of the host galaxy absorbers along with the QSO absorption line data provide a unique set of data to explore the gas flows in CGM. Here I present the results of our recent CGM studies using MUSE observations. In particular, I demonstrate the detailed analysis of a sightline where we find a bonafide candidate for the “cold-flow disk”.

Starburst galaxies at the zenith of the cosmic star-formation history are among the most   extreme star-forming engines in the universe. Their star formation rates, in the range  100–1000 solar mass per year, require large reservoirs of cold molecular gas to be delivered to their  compact cores in a sustained way over timescales of about 100 Myr, despite powerful feedback.  It is unclear how this is achieved. Because of its unique chemical and spectroscopic properties, CH⁺ unveils gas components invisible in CO emission: CH⁺ cannot form in cold  gas without supra-thermal energy input, so its presence highlights on-going dissipation of  mechanical energy or high UV-irradiation. The CH⁺ (J =1-0) line has a high critical density, so its detection in emission traces very dense gas, while absorption traces low-density gas.

We report ALMA detections of CH⁺ (J =1-0) lines in emission and absorption from  gravitationally lensed starburst galaxies  at redshifts between 2 and 4. The broad CH⁺ emission lines (linewidths > 1000 km/s) originate in a myriad of shocks, powered by massive stars and possibly active galactic nuclei. The CH⁺ absorption lines reveal highly turbulent reservoirs of diffuse gas, extending far out (> 10 kpc) the starburst cores of radii < 1kpc. We conclude that powerful galactic winds stir turbulence in the 10kpc-scale environment of the starburst cores, building up massive, multi-phase and gravitationally bound reservoirs that act as sustained mass and energy buffers to feed further star formation over the required timescales. In this picture, galactic feedback, mediated jointly by turbulence and gravity, extends the starburst phase instead of quenching it.

I will briefly introduce the ESA Gaia astrometric mission, its capabilities, science goals, and expected releases. I will then proceed to illustrate the potential and the limitations of Gaia data in crowded stellar regions, and in particular I will show some toy simulations of the Gaia science performances in globular-cluster-like fields.

The fine structure line [CII] at 158 microns is one of the brightest emission lines in the spectra of galaxies. It is considered to be the dominant coolant for neutral atomic gas in the interstellar medium. Conveniently, [CII] is redshifted into the sub-millimeter and millimeter atmospheric windows for 4.5<z<9. At high redshift, [CII] is thus a unique tracer of galaxy formation and a promising probe of the epoch of reionization (z>6). However, so far, [CII] studies of very distant
galaxies have been limited, with detection of only a handful of galaxies. The full power of ALMA will revolutionize the field, detecting [CII] in individual galaxies in the heart of the reionization era. However, while ALMA will probably follow-up hundreds of high-redshift galaxies, its small field of view and narrow bandwidth will strongly limit its sensitivity/efficiency to conduct large unbiased spectral line surveys.

Rather than detecting [CII] in selected galaxies, we propose to map in 3-D the intensity due to the [CII] line emission, a technique known as Intensity Mapping. This technique measures signal fluctuations produced by the combined emission of the galaxy population on large regions of the sky in a wide frequency (thus redshift) band, and thus increases sensitivity to faint sources. I will discuss how [CII] intensity mapping measurements can offer a straightforward alternative for tracing the
large structure of galaxies at z>4.5. By measuring [CII] fluctuations, I will show how we can obtain unprecedented constraints on star formation and dust build-up at a key epoch in the Universe. I will also discuss how cross-correlation of the signals (e.g. [CII] and galaxy surveys), as well as the lower redshift (z<2) CO-line fluctuations, could be used to
further understand the physics of galaxy formation and reionization. Finally I will present the CONCERTO experiment, a [CII] spectrometer capable of covering few square degrees with a high sensitivity and proposed as a new intensity mapping experiment.

Water is a key molecule in interstellar oxygen chemistry: it links grain-surface and gas-phase chemistry in molecular clouds, is a major gas coolant in star-forming regions, and plays a crucial role for life on Earth. Our understanding of where water is, and its abundance, particularly in star-forming regions, has increased manyfold with data from the Herschel Space Observatory. We are now approaching a complete picture of the water chemistry in star-forming regions, a picture which I will present.

In spite of our increased knowledge of the interstellar water chemistry, several open questions still remain regarding which physical components water traces near low-mass protostars. I will conclude the talk with an outlook of what can be done in the very near future with ALMA to address these questions, particularly with the new Band 5 receivers.

Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features found in the spectra of stars viewed trough one or several clouds of interstellar medium (ISM). Almost one century after their discovery the precise nature of their carriers (the agent originating these features) remains a mystery. Still, DIBs present good correlations with the amount of neutral hydrogen along a given line of sight, the extinction and the interstellar Na I D and Ca H&K lines. Thus, irrespective of the actual nature of carriers, DIBs can be used to trace the structure of the ISM in the same way as others species, and they even offer certain advantages when used instead of (or in addition to) other tracers. In this lunch talk, I will present our on going work to use both optical and infrared DIBs to trace the ISM in our Galaxy.

I will present recent results from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database: the largest collection of mass models currently available for late-type galaxies (spirals and irregulars) at z=0. HI/Ha rotation curves provide the centripetal acceleration (gobs) at different radii, while Spitzer photometry at 3.6 um allows us to precisely estimate the baryonic gravitational field (gbar). We find that gobs tightly correlates with gbar over 4 dex. The correlation persists even when dark matter dominates. The observed scatter is remarkably small (0.13 dex) and largely driven by observational uncertainties. Early-type galaxies and dwarf spheroidals follow the same relation as late-type galaxies. The radial acceleration relation is tantamount to a "Kepler Law" for galactic systems: when the baryonic contribution is measured, the rotation curve follows, and vice versa.

It now seems that Cosmic Rays (CRs) can destroy the CO molecule in star forming galaxies very effectively, potentially rendering large H2 gas distributions (CO-line)-invisible, especially in the so-called Main Sequence (MS) galaxies. I will discuss the chemistry behind it and a way out in re-acquiring the CO-invisible H2 gas distributions in galaxies. Finally the effects of CRs in resetting the initial conditions for star formation in galaxies will be discussed, along observations that may have started revealing this already.

I will present results based on sub-arcsecond resolution observations of massive Young Stellar Objects (YSOs) in the Magellanic Clouds. I will start by briefly describing the background and context for this study. The observations, carried out in the NIR with SINFONI at the VLT, reveal a wide variety of spatially extended emission line morphologies, indicative of outflows and compact HII regions. Through a comparison of massive YSOs in the Magellanic Clouds and a Galactic sample, evidence of significantly enhanced accretion rates towards the YSOs in the Magellanic Clouds is detected. Whilst the underlying mechanism of this enhancement is uncertain, there appears to be a convincing correlation between metallicity and accretion rates in massive YSOs.

​Through analysis of the ancillary optical spectra in the context of the SINFONI data the massive YSOs in the SMC appear to reside in a porous ISM, allowing a large mean-free-path for energetic photons.​ These results have been published by Ward et al. (2016, 2017).

Evolved hot, luminous stars are known to drive strong mass loss
(10^{^-10} - 10-5 Msol /yr) from their surfaces through UV-scattering
forces. These same forces also efficiently ablate material o ff the
surface of circumstellar disks, both in the late phases of massive
star formation, and during the main sequence phase of Classical Oe and
Be stars. By using a fully three-dimensional UV-scattering
prescription (Castor, Abbott, and Klein 1975; Cranmer and Owocki
1995), we here quantify the role of radiative ablation in removing
material from such disks, focusing on results for Classical Oe and Be
stars (Kee et al. 2016).