Galaxy formation is a very complex process in which many different physical mechanisms intervene. Within the LCDM paradigm processes such as gas inflows and outflows, mergers and interactions contribute to the redistribution of the angular momentum content of the structures. Recent observational results have brought new insights and also triggered several theoretical studies. Some of these new contributions will be analysed here.

Photographic plate archives contain a wealth of information about the positions and brightness of celestial objects decades ago. Plate digitization is necessary to make this information accessible, but extracting it is a technical challenge. We have developed algorithms to extract photometry with an accuracy of better than ∼0.1 mag. in the range 13 < B < 17 mag from photographic images obtained in 1948–1996 with the 40-cm Sternberg Institute astrograph (30 × 30 cm plate size, 10 × 10 deg field of view) and digitized using a flatbed scanner. The extracted photographic light-curves are used to identify thousands of new high-amplitude variable stars (>0.2 mag). The algorithms are implemented in the free software VaST available at http://scan.sai.msu.ru/vast/

We report long-term observations of H2O and OH maser emission sources at wavelengths of 1.35 and 18 cm associated with star-forming regions. Strong quasi-periodic flares of maser emission have been observed. Several sources (in particular, G25.65+1.05, IRAS 16293−2422, Cep A) have displayed strong flares in the H2O line, when their peak flux density raised by a few orders of magnitude above the quiet state. Possible causes of this are discussed.

Blue compact dwarf galaxies(BCDs) are galaxies undergoing violent burst of star formation in compact regions. They are often thought of being an evolutionary stage of dwarf galaxies and thus can provide a unique window to study the formation and evolution of dwarf galaxies. We selected a sample of 48 BCDs from the SDSS-IV MaNGA survey (MPL-7) and separated the starburst(SB) components from their underlying hosts with a new algorithm. Combining the structural properties of the BCDs, we further explore the physical connections between the SB components and theirs hosts.

We present ALMA band 7 data of the extreme OH/IR star, OH 26.5+0.6. In addition to lines of CO and its isotopologues, the circumstellar envelope also exhibits a number of emission lines due to metal-containing molecules, e.g., NaCl and KCl. A lack of C18O is expected, but a non-detection of C17O is puzzling given the strengths of H217O in Herschel spectra of the star. However, a line associated with Si17O is detected. We also report a tentative detection of a gas-phase emission line of MgS. The ALMA spectrum of this object reveals intriguing features which may be used to investigate chemical processes and dust formation during a high mass-loss phase.

Using direct N-body simulations of self-gravitating systems we study the dependence of dynamical chaos on the system size N. We find that the N-body chaos quantified in terms of the largest Lyapunov exponent Λmax decreases with N. The values of its inverse (the so-called Lyapunov time tλ) are found to be smaller than the two-body collisional relaxation time but larger than the typical violent relaxation time, thus suggesting the existence of another collective time scale connected to many-body chaos.

Throughout the Hubble time, gas makes its way from the intergalactic medium into galaxies fuelling their star formation and promoting their growth. One of the key properties of the accreting gas is its angular momentum, which has profound implications for the evolution of, in particular, disc galaxies. Here, we discuss how to infer the angular momentum of the accreting gas using observations of present-day galaxy discs. We first summarize evidence for ongoing inside-out growth of star forming discs. We then focus on the chemistry of the discs and show how the observed metallicity gradients can be explained if gas accretes onto a disc rotating with a velocity 20 – 30% lower than the local circular speed. We also show that these gradients are incompatible with accretion occurring at the edge of the discs and flowing radially inward. Finally, we investigate gas accretion from a hot corona with a cosmological angular momentum distribution and describe how simple models of rotating coronae guarantee the inside-out growth of disc galaxies.

With the hundreds of merging binary black holes (BHs) expected to be detected by LIGO, LISA, and other upcoming instruments, the modelling of astrophysical channels that lead to the formation of compact BH binaries has become of crucial importance. BHs of any size can form bound systems in every astrophysical environment, from the field to galactic nuclei. If a binary is too wide, it needs a catalysis process to harden and merge, as in the case a third objects orbiting the BH binary on a distant orbit. In this case, Kozai-Lidov cycles can pump up the binary eccentricity, thus driving it to a merger thanks to efficient energy dissipation at the pericenter. Some remarkable scenarios where the Kozai-Lidov mechanism operates are in triple and quadruple systems of stellar BHs, and in intermediate-mass BH-stellar BH binaries in orbit around a central supermassive BH in galactic nuclei.

The All-Sky Automated-Survey for SuperNovæ (ASAS-SN) is a fully automated transient search programme that is currently observing the entire night sky every second night to a depth of about 18th magnitude. Since becoming on-line in mid-2014, ASAS-SN has discovered over half of all bright supernovæ, and along the way has also discovered numerous tidal disruption events, cataclysmic variables, stellar flares and even a comet! ASAS-SN currently has two units deployed between Chile and Hawaii, and an additional three units were slated to come on-line by the end of 2017 at observatories in South Africa, Chile and Texas. The poster provided a brief summary of ASAS-SNs accomplishments, and discussed future prospects based on its global expansion.

Dwarf galaxies represent the dominant population at high redshift and they most likely contributed in great part to star formation history of the Universe and cosmic reionization. The importance of dwarf galaxies at high redshift has been mostly recognized in the last decade due to large progress in observing facilities allowing deep galaxy surveys to identify low-mass galaxies. This population appear to have extreme emission lines and ionizing properties that challenge stellar population models. Star formation follows a stochastic process in these galaxies, which has important implication on the ionizing photon production and its escape fraction whose measurements are challenging for both simulations and observations. Outstanding questions include: what are the physical properties at the origin of such extreme properties? What are the smallest dark matter halos that host star formation? Are dwarf galaxies responsible for cosmic reionization?

Recently a large number of Galactic cold clumps were located with the Planck all-sky survey. Our radio line observations have revealed the distribution and physical properties of the interstellar medium in dozens of PGCC sources. Clumps can be affected by many external effects. HCL1 (a.k.a. L1251) and HCL2 (which contains also TMC-1) are examples of low mass star forming clouds in violent and quiet environments.

We determine Zr and Nb elemental abundances in barium stars to probe the operation temperature of the s-process that occurred in the companion asymptotic giant branch (AGB) stars. Along with Zr and Nb, we derive the abundances of a large number of heavy elements. They provide constraints on the s-process operation temperature and therefore on the s-process neutron source. The results are then compared with stellar evolution and nucleosynthesis models. We compare the nucleosynthetic profile of the present sample stars with those of CEMP-s, CEMP-rs and CEMP-r stars. One barium star of our sample is potentially identified as the highest-metallicity CEMP-rs star yet discovered.

Planck cold clump G163.82-8.44 is part of the Auriga-California Molecular Cloud. It was observed with Herschel PACS and SPIRE instruments as part of the Herschel open time key programme Galactic Cold Cores. Follow-up ground-based molecular line observation of NH3 was performed to the densest part of the filament with the Effelsberg-100m telescope. We detected two different velocity components with a separation of 0.5 km/s. We performed radiative transfer modeling with two 3-dimensional spheres to characterise the temperature and density of the dense cores. We have found that the temperatures of the two cores are almost the same, 10.8 K and 11.1 K and their mass and size ratios are 1:10 and 1:5, respectively.

N-body simulation is the necessary tool to investigate the evolution of star clusters. It is important to develop a time integration method which guarantees the appropriate accuracy and calculation cost.

Here we present a new simple method for long term simulation of stars around a massive black hole in stellar systems. Usually the time integration orbits of stars revolving a massive black hole requires much simulation time. We introduce a time transformation which is a kind of ”inverse KS regularization” of time. Using our method, the integration of the long term evolution near a black hole (BH) becomes easier, especially applied to relatively large star clusters and the Galactic Center.

The overwhelming majority of galaxies in the Universe are dwarf galaxies. But although they are important components in understanding galaxy evolution, these systems are typically too faint to be observed at high redshifts. However, we are able to obtain an unobscured view of early star formation and chemical enrichment in these galaxies at low redshift and low-redshift analogs at high redshift. In this talk, I will review the mass-metallicity relation, the mass-star formation rate relation of galaxies, the classifications of dwarf galaxies, and the importance of dwarf galaxies for both astronomy and physics. Then I will introduce some work in our group on connections among between different types of dwarf galaxies,the mass-metallicity relations and the main sequence relations of dwarf galaxies, using the deep optical and near infrared images and spectra of large dwarf galaxy sample. At the end, I will talk about some projects of dwarf galaxies we are working on, including the spectroscopic survey for compact dwarf galaxies using the LAMOST.

A tomographic method, aiming at probing velocity fields at depth in stellar atmospheres, is applied to the red supergiant star μ Cep and to snapshots of 3D radiative-hydrodynamics simulation in order to constrain atmospheric motions and relate them to photometric variability.

With so many spectroscopic surveys, both past and upcoming, such as SDSS and LAMOST, the number of accessible stellar spectra is continuously increasing. There is therefore a great need for automated procedures that will derive estimates of stellar parameters. Working with spectra from SDSS and LAMOST, we put forward a hybrid approach of Kernel Principal Component Analysis (KPCA) and Support Vector Machine (SVM) to determine the stellar atmospheric parameters effective temperature, surface gravity and metallicity. For stars with both APOGEE and LAMOST spectra, we adopt the LAMOST spectra and APOGEE parameters, and then use KPCA to reduce dimensionality and SVM to measure parameters. Our method provides reliable and precise results; for example, the standard deviation of effective temperature, surface gravity and metallicity for the test sample come to approximately 47–75 K, 0.11–0.15 dex and 0.06–0.075 dex, respectively. The impact of the signal:noise ratio of the observations upon the accuracy of the results is also investigated.

We investigate the dissolution process of star clusters embedded in an external tidal field and harboring a subsystem of stellar-mass black hole. For this purpose we analyzed the MOCCA models of real star clusters contained in the Mocca Survey Database I. We showed that the presence of a stellar-mass black hole subsystem in tidally filling star cluster can lead to abrupt cluster dissolution connected with the loss of cluster dynamical equilibrium. Such cluster dissolution can be regarded as a third type of cluster dissolution mechanism. We additionally argue that such a mechanism should also work for tidally under-filling clusters with a top-heavy initial mass function.

Formaldehyde (H2CO) and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Our recent single dish observation of formaldehyde and its deuterated species suggests that they form mostly on grain surfaces although some gas-phase contribution is expected at the warm HMPO stage. Since the single dish beam is larger, and since these high-mass star-forming regions are clustered and complex, it is however unclear whether the emission arises from the protostellar sources or from starless/pre-stellar cores associated with them. Therefore, interferometric observations are needed to separate the emission originating from the small and dense cores, to disentangle their formation routes and then being able to use them as powerful diagnostic tools of the physical and chemical properties of high-mass star forming regions.