Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global starformation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallowpotential wells, and observational measures of their prevalence inform our understanding of a wide range of issues ingalaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxiesin the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths ofmassive stars may further our understanding of open issues in galaxy evolution.

The intensity ratios of HCO+/HCN and HNC/HCN (1-0) reveal the relative influence of star formation and active galactic nuclei (AGN) or black holes on the circum-nuclear gas of a galaxy, allowing the identification of X-ray dominated regions (XDRs) and Photon-dominated regions (PDRs). It is not always clear in the literature how this intensity ratio calculation has been, or should be performed. This paper discusses ratio calculation methods for interferometric data.

ChemiX is a Bragg crystal spectrometer that will fly on the two Interhelioprobe spacecraft due for launch in 2025 and 2026. The spacecraft perihelion will be only 0.3 a.u. and the orbit inclination up to 30°, and so instruments on board will have a close view of solar active regions and flares and regions near each solar pole. The ChemiX X-ray spectrometer, built by a consortium of groups led by the Space Research Centre, Polish Academy of Sciences, will fly on each of the spacecraft, and observe X-ray spectra in the 1.5 - 9 Å range. Spectral lines in this range include resonance lines of helium-like and hydrogen-like ions of elements such as Fe, Ca, Ar, S, and Si, with less abundant elements such as K and Cl represented by weaker lines which the high sensitivity of ChemiX should be able to detect. The free–free and free–bound continua should also be detected since instrumental background will be eliminated. Three of the seven channels of ChemiX will be in a “dopplerometer” arrangement by which spatial and spectral shifts present in flare impulsive stages can be disentangled.

We found that star-forming regions in extended ultraviolet (XUV) disks are generally consistent with the molecular-hydrogen Kennicutt-Schmidt law that applies within the inner, optical disk. This is true for star formation rates based on Hα + 24 μm data or FUV + 24 μm data. We estimated that the star-forming regions have ages of 1 − 7 Myr and propose that the presence or absence of molecular gas provides an additional “clock” that may help distinguish between aging and stochasticity as the explanation for the low Hα-to-FUV flux ratios in XUV disks. This contribution is a summary of the work originally presented in Watson et al. (2016).

We probe many kinds of approaches used for photometric redshift estimation of quasars, including KNN (K-nearest neighbor algorithm), Lasso (Least Absolute Shrinkage and Selection Operator), PLS (Partial Least Square regression), ridge regression, SGD (Stochastic Gradient Descent) and Extra-Trees.

The local dark matter density plays the key role in the distribution of the dark matter halo near the Galactic disk. It will also answer whether a dark matter disk exists in the Milky Way. We measure the local dark matter density with LAMOST observed stars located at around the north Galactic pole. The selection effects of the observations are well considered and corrected. We find that the derived DM density, which is around 0.0159+0.0047−0.0057M⊙ pc−3 providing a flat local rotation curve.

The early Solar system produced a variety of bodies with different properties. Among the small bodies, objects that contain notable amounts of water ice are of particular interest. Water-rock separation on such worlds is probable and has been confirmed in some cases. We couple accretion and water-rock separation in a numerical model. The model is applicable to Ceres, icy satellites, and Kuiper belt objects, and is suited to assess the thermal metamorphism of the interior and the present-day internal structures. The relative amount of ice determines the differentiation regime according to porous flow or Stokes flow. Porous flow considers differentiation in a rock matrix with a small degree of ice melting and is typically modelled either with the Darcy law or two-phase flow. We find that for small icy bodies two-phase flow differs from the Darcy law. Velocities derived from two-phase flow are at least one order of magnitude smaller than Darcy velocities. The latter do not account for the matrix resistance against the deformation and overestimate the separation velocity. In the Stokes regime that should be used for large ice fractions, differentiation is at least four orders of magnitude faster than porous flow with the parameters used here.

We take a closer look at the dependence of the galactic colour histogram on the environment density using a volume-limited sample of SDSS galaxies. We find that the strongest changes with environment are taking place with spiral galaxies. In dense environment, discs become considerably redder, apparently due to the shortage of gas, and less concentrated. Contrary to expectation, the mean Sérsic index of luminous elliptical galaxies decreases in denser environments.

Molecular gas has still only been detected beyond the R25 radius in a few galaxies. Is this due to the low H2 content or to the difficulty of using Carbon Monoxide (CO) to trace H2? Similarly, star formation (SF) decreases sharply in the outer disks of spirals although HI is often plentiful; is the decrease in SF because there is little H2 or because the SF is very inefficient in the outer disk environment?

Existing observations suggest that while outer disk clouds tend to be smaller (steeper mass function), their CO brightness temperature is only slightly lower than in the inner disk, at least when observed with sufficiently high angular resolution. In near-solar metallicity galaxies (Z ⩾ 0.5Zsol), the CO does not become intrinsically difficult to detect when H2 is present, even in the outer disk. While more observations of CO or other means of tracing H2 in the outer disks are necessary, current data tend to show that the SF rate per unit H2 remains approximately constant with galactocentric distance, indicating that the star formation proceeds normally but the transformation of HI into H2 is very slow in the outer disk.

I review the recent observational progresses of star-forming galaxies at a redshift up to z~10. Inconjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD)continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by thecombination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple thecontribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) ofhigh-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo massrelation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different betweenthe present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedbacksignatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with andwithout an AGN heating. There are similarly-large hydrogen Lyα halos and blobs associated with high-z star-forminggalaxies, but the physical origin of these Lyα halos and blobs is an open question. At z≳6, UV radiation of ionizingphotons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UVradiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as acosmological feedback effect. I discuss this reionizations cosmological feedback effect with the up-to-date resultsfrom the HST and Planck data.

The properties of galaxies depend on their environment: red, passive elliptical galaxies are usually located in denser environments than blue, star-forming spiral galaxies. This difference in galaxy populations can be detected at all scales from groups of galaxies to superclusters. In this paper, we will discuss the effect of the large-scale environment on galaxies. Our results suggest that galaxies in superclusters are more likely to be passive than galaxies in voids even when they belong to groups with the same richness. In addition, the galaxies in superclusters are also affected by the morphology of the supercluster: filament-type superclusters contain relatively more red, passive galaxies than spider-type superclusters. These results suggest that the evolution of a galaxy is not determined by its local environment alone, but the large-scale environment also affects.

Planets form in disks around young stars. In these disks, condensation fronts or snowlines of water, CO2, CO and other abundant molecules regulate the outcome of planet formation. Snowline locations determine how the elemental and molecular compositions of the gaseous and solid building blocks of planets evolve with distance from the central star. Snowlines may also locally increase the planet formation efficiency. Observations of snowlines have only become possible in the past couple of years. This proceeding reviews these observations as well as the theory on the physical and chemical processes in disks that affect snowline locations.

We have constructed two types of analytical models for an isothermal filamentary cloud supported mainly by magnetic tension. The first one describes an isolated cloud while the second considers filamentary clouds spaced periodically. The filamentary clouds are assumed to be highly flattened in both the models. The former is proved to be the asymptotic limit of the latter in which each filamentary cloud is much thinner than the distance to the neighboring filaments. These models show that the mass to flux ratio is crucial for the magnetohydrodynamical equilibrium. The upper bound for the line density, i.e., the mass per unit length, is proportional to the magnetic flux. The mass to flux ratio is slightly larger than the critical value, ($2 \pi \sqrt{G}$)−1, in the first model and lower in the second model. The first model is unstable against fragmentation and the wavelength of the fastest growing mode is several times longer than the cloud diameter. The second model is likely to be unstable only when the mass to flux ratio is supercritical.

We find that for the galaxy groups, the luminosity gap between the brightest and the subsequent brightest member galaxies in a halo (group) can be used to significantly reduce the scatter in the halo mass estimation based on the luminosity of the brightest galaxy alone. These corrections can significantly reduce the scatter in the halo mass estimations by ~ 50% to ~ 70% in massive halos.

Excellent sites are necessary for developing and installing ground-based large telescopes. For very-high-resolution solar observations, it had been unclear whether there exist good candidate sites in the west areas in China, including the Tibetan Plateau and the Pamirs Plateau. The project of solar site survey for the next-generation large solar telescopes, i.e., the Chinese Giant Solar Telescope (CGST) and the large coronagraph, has been launched since 2011. Based on the close collaboration among Chinese solar society and the scientists from NSO, HAO and other institutes, we have successfully developed the standard instruments for solar site survey and applied them to more than 50 different sites distributed in Xinjiang, Tibet, Qinghai, Sichuan, Yunnan and Ningxia provinces. We have built two long-term monitoring sites in Tibet and the large Shangri-La to take systematic site data. Clear evidence, including the key parameters of seeing factor, sky brightness and water vapor content, has indicated that a few potential sites in the large Tibetan areas should obtain the excellent astronomical conditions for our purpose to develop CGST and large coronagraph. We introduce the fresh site survey results in this report.

High-mass stars usually form in giant molecular clouds (GMCs) as part of a young stellar cluster, but some isolated O/B stars are observed. What are the initial conditions that lead to the formation of these objects? The aim of this study is to measure the distribution and basic physical properties of the neutral gas associated with isolated intermediate- and high-mass young stellar objects (YSOs) in the Large Magellanic Cloud.

As part of the SAGE Spitzer Legacy program for the LMC, we have identified and confirmed YSOs using Spitzer IRAC photometry and IRS spectroscopy. By examining the spatial coincidence between the YSOs and 12CO(1–0) emission detected by the NANTEN mapping survey, we identified more than one hundred intermediate/massive YSOs in the LMC that appear to be isolated, i.e. not associated with CO emission. Deeper follow-up CO observations by our team with the higher resolution by Mopra Telescope (beam=30”) detected CO emission at the YSO positions for ~80% of the isolated LMC YSOs. We obtained ALMA data of some of the targets during Cycle 2. We targeted a small but representative (in terms of their association with neutral gas tracers) sample of the isolated high-mass YSOs that we have been studying in the LMC. All of our 12 targets are separated by more than 200 pc from known CO clouds. Our analysis of the ALMA data shows that a compact molecular cloud whose mass is a few thousand solar masses or smaller is associated with most of the YSOs.

Gamma-ray burst host galaxies are deficient in molecular gas, and show anomalous metal-poor regions close to GRB positions. Using recent Australia Telescope Compact Array (ATCA) Hi observations we show that they have substantial atomic gas reservoirs. This suggests that star formation in these galaxies may be fuelled by recent inflow of metal-poor atomic gas. While this process is debated, it can happen in low-metallicity gas near the onset of star formation because gas cooling (necessary for star formation) is faster than the Hi-to-H2 conversion.

We briefly review what is currently known of 14N/15N ratios in interstellar molecules. We summarize the fractionation ratios measured in HCN, HNC, CN, N2 and NH3, and compare these to theoretical predictions and to the isotopic inventory of cometary volatiles.

In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a “tilted ring model” allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.