The CO-to-H2 conversion factor (αCO) is crucial for accurate estimation of the amount and properties of molecular gas. However, αCO is known to vary with environmental conditions, and previous kpc-scale studies have revealed lower αCO in the centers of some barred galaxies, including NGC 3351, 3627, and 4321. We present ALMA Band 3, 6, and 7 observations toward the inner ∼2 kpc of these galaxies tracing 12CO, 13CO, and C18O lines at ∼100 pc resolution. We show that dynamical effects resulting from turbulence/shear can lead to substantially lower αCO in the bar-driven inflows of NGC 3351 due to lower optical depth. A clear, positive correlation between αCO and 12CO optical depth is seen in all three galaxy centers. We also find that the CO/13CO(2–1) ratio mainly traces the 12CO optical depth, and thus it may be a useful observable in predicting αCO variation in galaxy centers.

We investigated the evolution of HS Hya system’s inclination based on analysis of its light curves in the period 1964–2021. HS Hya is EA type eclipsing binary star, belonging to separate group with changing orbital inclination. We used our recent observations as well as the data from sky surveys.

Feedback from supernovae (SNe) is an essential mechanism that self-regulates the growth of galaxies. We build an SN feedback model based on high-resolution simulations of superbubble and SN-driven outflows for the physical understanding of the galaxy–CGM connection. Using an Eulerian hydrodynamic code Athena++, we find universal scaling relations for the time evolution of superbubble momentum, when the momentum and time are scaled by those at the shell-formation time. We then develop an SN feedback model utilizing Voronoi tessellation, and implement it into the GADGET3-Osaka smoothed particle hydrodynamic code. We show that our stochastic thermal feedback model produces galactic outflow that carries the metals high above the galactic plane but with weak suppression of star formation. Additional mechanical feedback further suppresses star formation. Therefore, we argue that both thermal and mechanical feedback is necessary for the SN feedback model of galaxy evolution when an individual SN bubble is unresolved.

Due to observational constraints, our detailed knowledge of stellar populations, formation, and evolution of galaxies is limited to a few dozen galaxies located in the Local Group. The Local Group of galaxies offers a unique opportunity to construct the formation histories and probe the structure and dynamics of many dwarf galaxies surrounding the Milky Way and Andromeda and of isolated dwarf galaxies. In this regard, we monitored the majority of galaxies in the Local Group, including the M33 galaxy and satellites galaxies surrounding the Milky Way and Andromeda galaxy, as well as isolated dwarf galaxies. We identified stellar populations and based on light curve analysis, the cool evolved stars pulsating in the fundamental mode were identified. In this paper, first, we will present the results we obtained for SFH and dust production rate in individual galaxies separately to answer how different types of galaxies have been formed and evolved over cosmic time. Then, we will discuss whether the mass return from dusty evolved stars can provide enough gas reservoirs to sustain the star formation or even rejuvenate the dwarf galaxy, as some seem to harbor relatively young stars.

In this invited review talk I summarize some of the recent observational advances in understanding mass loss from low-mass stars. This can take the form of a relatively steady wind, or stochastically occurring coronal mass ejections (CMEs). In recent years, there has been an expansion of observational signatures used to probe mass loss in low-mass stars. These observational tools span the electromagnetic spectrum. There has also been a resurgence of interest in this topic because of its potential impact on exoplanet space weather and habitability. The numerous recent observational and theoretical results also point to the complexities involved, rather than using simple scalings from solar understanding. This underscores the need to understand reconnection and eruption processes on magnetically active stars as a tool to putting our Sun in context.

The long-term behavior of a colliding wind binary WR 25 is presented using archival X-ray data obtained over a time span of : 16 years. The present analysis reveals phase-locked variations repeating consistently over many consecutive orbits of the source (with binary orbital period : 208 days). A significant deviation of the X-ray flux with respect to the theoretical 1/D trend (D is the binary separation) close to periastron passage has been observed. This may occur due to the shifting of the adiabatic wind collision to the radiative regime in that part of the orbit. Further, no signature of X-ray emission in 10.0-79.0 keV energy range attributable to inverse Compton scattering is detected by NuSTAR.

We explore the relationship between globular cluster total number, NGC, and central black hole mass, M•, in spiral galaxies. Including cosmic scatter, log M• ∝ (1.64 ± 0.24) log NGC. Whereas in ellipticals the correlation is linear [log M• ∝ (1.02 ± 0.10) log NGC], and hence could be due to statistical convergence through mergers, this mechanism cannot explain the much steeper correlation in spirals. Additionally, we derive total stellar galaxy mass, M*, from its two-slope correlation with NGC (Hudson et al. 2014). In the M• versus M* parameter space, with M* derived from NGC, M• ∝ (1.48 ± 0.18) log M* for ellipticals, and M• ∝ (1.21 ± 0.16) log M* for spirals. The observed agreement between ellipticals and spirals may imply that black holes and galaxies co-evolve through “calm” accretion, AGN feedback and other secular processes.

We studied the problem of two spherical celestial bodies in the general case when the masses of the bodies change non-isotropically at different rates in the presence of reactive forces. The problem was investigated by methods of perturbation theory based on aperiodic motion along a quasi-conic section, using the equation of perturbed motion in the form of Newton’s equations. The problem is described by the variables a, e, i, π, ω, λ, which are analogs of the corresponding Keplerian elements and the equations of motion in these variables are obtained. Averaging over the mean longitude, we obtained the evolution equations of the two-body problem with variable masses in the presence of reactive forces. The obtained evolution equations have the exact analytic integral ${a^3 e^4 = a^3_0 e^4_0} = {const}$.

We studied the probability distribution function of the column density (N-PDF) of molecular clouds based on a fit with a multi-log-normal function using the Nobeyama 45-m Cygnus X CO survey data. We identified 124 molecular clouds in 13CO data using the DENDROGRAM and SCIMES algorithms. The N-PDF was constructed for 11 extended (≥ 0.4 deg2) molecular clouds of these identified clouds. We found that every N-PDF is well-fitted with one or two log-normal (LN) distributions. We investigated the distributions of the column density, C18O dense cores, and radio continuum source in each cloud and found that the N-PDF was less correlated with the star-forming activity. The LN N-PDF parameters showed two impressive features. First, the LN distribution at the low-density part had the same mean column density (∼1021.5 cm−2 ) for almost all the molecular clouds. Second, the wider LN distribution tended to show the lower mean density of the structures.

Star formation laws are empirical relations between the cold gas (HI+H2) content of a galaxy and its star formation rate (SFR), being crucial for any model of galaxy formation and evolution. A well known example of such laws is the Schmidt-Kennicutt law, which is based on the projected surface densities. However, it has been long unclear whether a more fundamental relation exists between the intrinsic volume densities. By assuming the vertical hydrostatic equilibrium, we infer radial profiles for the thickness of gaseous discs in a sample of 23 local galaxies, and use these measurements to convert the observed surface densities of the gas and the SFR into the de-projected volume densities. We find a tight correlation linking these quantities, that we call the volumetric star formation law. This relation and its properties have crucial implications for our understanding of the physics of star formation.

We report a CO(3-2) detection of 23 molecular clouds in the extended ultraviolet (XUV) disk of the spiral galaxy M83 with ALMA. The observed 1 kpc2 region is at about 1.24R25 from the disk center, where CO(2-1) was previously not detected. The detection and non-detection, as well as the level of star formation (SF) activity in the region, can be explained consistently if the clouds have the mass distribution common among Galactic clouds, such as Orion A – with star-forming dense clumps embedded in thick layers of bulk molecular gas, but in a low-metallicity regime where their outer layers are CO-deficient and CO-dark. The cloud masses, estimated from CO(3-2), range from 8.2×102 to 2.3×104M⊙. The most massive clouds appear similar to Orion A in SF activity as well as in gas mass. The common cloud mass structure also justifies the use of high-J CO transitions to trace the total gas mass of clouds, or galaxies, even in the high-z universe. This study is the first demonstration that CO(3-2) is an efficient tracer of molecular clouds even in low-metallicity environments. This study is published in the Astronomical Journal, entitled “First Detection of the Molecular Cloud Population in the Extended Ultraviolet (XUV) Disk of M83" by J. Koda, L. Watson, F. Combes, M. Rubio, S. Boissier, M. Yagi, D. Thilker, A. M Lee, Y. Komiyama, K. Morokuma-Matsui, and C. Verdugo.

Red supergiants (RSGs) are evolved massive stars in a stage preceding core-collapse supernova. Understanding evolved-phases of these cool stars is key to understanding the cosmic matter cycle of our Universe, since they enrich the cosmos with newly formed elements. However, the physical processes that trigger mass loss in their atmospheres are still not fully understood, and remain one of the key questions in stellar astrophysics. We use a new method to study the extended atmospheres of these cold stars, exploring the effect of a stellar wind for both a simple radiative equilibrium model and a semi-empirical model that accounts for a chromospheric temperature structure. We then can compute the intensities, fluxes and visibilities matching the observations for the different instruments at the Very Large Telescope Interferometer (VLTI). Specifically, when comparing with the atmospheric structure of HD 95687 based on published VLTI/AMBER data, we find that our model can accurately match these observations in the K-band, showing the enormous potential of this methodology to reproduce extended atmospheres of RSGs.

The evolution of star formation properties of galaxies depends on the environment where galaxies reside, and generally star formation of galaxies in dense environment decreases more quickly. Interestingly, the star formation property of high-redshift galaxies clusters vary largely even though they are at similar redshift. We have found that the large-scale environment surrounding each galaxy cluster can contribute to make this cluster-by-cluster variation. This correlation is found in the results from observational data as well as in the simulations of galaxy formation. We suggest the ‘Web-feeding model’ to explain this trend. Star-forming galaxies falling into the galaxy cluster from surrounding large-scale structure make the quiescent galaxy fraction of the cluster lower than relatively isolated clusters.

Ultra-luminous infrared galaxies (ULIRGs) are extreme in many ways. The major mergers trigger star formation at very high rates that cause the ISM to be dominated by infrared (IR) photons. We show the ammonia spectra toward the two cores of Arp 220, the nearest ULIRG, in three Very Large Array (VLA) bands (Ku, K, Ka). Typical decay times of the non-metastable transitions ∼ 100 s and are therefore usually difficult to observe. The FIR excitation of Arp 220, however, shows that non-metastable states are widely populated up to a limiting energy of ∼ 1500 K. We assume that this atypical ammonia spectrum is due to the strong FIR field that re-excites the ammonia molecule on timescales much shorter than the already short decay times. The resulting level population causes a break-down of the typical assumptions made for the use of ammonia as a molecular thermometer.

Jellyfish galaxies are starburst galaxies with ram-pressure-stripped tails and blue star-forming knots. These galaxies show a snapshot of star formation enhancement triggered by ram pressure stripping (RPS), being important targets for studying the RPS-induced star formation in gas-rich galaxies. Here we investigate the star formation activity of five jellyfish galaxies in massive clusters, using Gemini GMOS/IFU observations. From the Hα-derived star formation rates (SFRs), we find that our sample shows higher SFR excess to the star formation main sequence than the jellyfish galaxies in low-mass clusters. From the compiled sample of jellyfish galaxies in low-mass to high-mass host clusters, we suggest that the star formation activity of jellyfish galaxies has positive correlations with host cluster mass and degree of RPS. These relationships imply that higher ram pressure environments tend to trigger stronger starbursts in jellyfish galaxies in the early stage of RPS.

Galaxies, particularly disc galaxies, show a wide variety of internal structures (e.g. spirals, bars, and bulges). Mapping Nearby Galaxies at Apache Point Observatory (MaNGA, part of the fourth incarnation of the Sloan Digital Sky Surveys), obtained spatially resolved spectral maps for 10,010 nearby galaxies. Many results from MaNGA have collapsed this structure into azimuthally averaged radial gradients, or symmetric 2D shapes, but there is significantly more information about the effect internal structures have on the evolution of galaxies available if we can identify different internal structures. One of the simplest ways to identify irregular internal structures in galaxies is by visual inspection. By employing a citizen science technique to ask this question of N independent volunteers we have obtained quantitatively robust masks (and errors) for spirals and bars in MaNGA target galaxies. In addition to internal features the interface asked users to identify foreground stars and foreground/background galaxies.

Atmospheric escape has traditionally been observed using hydrogen Lyman-α transits, but more recent detections utilise the metastable helium triplet lines at 1083nm. Capable of being observed from the ground, this helium signature offers new possibilities for studying atmospheric escape. Such detections are dependent however on the specific high-energy flux received by the planet. Previous studies show that the extreme-UV band both drives atmospheric escape and populates the triplet state, whereas lower energy mid-UV radiation depopulates the state through photoionisations. This is supported observationally, with the majority of planets with 1083nm detections orbiting a K-type star, which emits a favourably high ratio of EUV to mid-UV flux. The goal of our work is understanding how the observability of escaping helium evolves. We couple our one-dimensional hydrodynamic non-isothermal model of atmospheric escape with a ray-tracing technique to achieve this. We consider the evolution of the stellar radiation and the planet’s gravitational potential.

We draw the K-band luminosity functions (CLFs) of young massive clusters (YMCs) hosted by 34 SUNBIRD targets to evaluate the impact of the host galaxy environment on their YMC properties. The depth and high resolution of the NIR images (PSF ∼ 0.1”) allow us to test whether CLF power-law slopes (α) of high star-forming galaxies are similar to those of gas-poor low star formation rate (SFR) galaxies. We found that α ranges between 1.53 and 2.41 with a median value of 1.87 ± 0.23. We also performed correlation searches between α and the host global properties and noticed that α decreases with an increasing SFR and SFR density. On sub-galactic scales, CLF slopes of cluster-rich galaxies differ by ∼0.5. Our NIR CLF analyses suggest that the extreme environment of high SFR galaxies such as the SUNBIRD sample is likely to affect the formation mechanisms of YMCs and hence to govern the ongoing small-scale SF processes of the host galaxy.

Detection of transients such as supernovae (SNe) and kilonovae (KNe) in early phase has recently become important for understanding the progenitor properties and multi-messenger astronomy. Predicting which galaxy has the higher probability of hosting the transient events would help detect the early phase of the events and get information on their progenitors. The SN and KN rates are known to be a function of star formation rate (SFR) and stellar mass of the host galaxy. The SFR of a galaxy can be estimated from ultraviolet (UV) luminosity. However, the UV magnitudes have been derived carefully only for a limited number of nearby galaxies. Here, we introduce GALEX galaxy catalog of all-sky UV brightness of low redshift galaxies. To do so, we derive the UV photometry of galaxies in the GLADE catalog using the GALEX AIS images, supplemented by GALEX NGS and MIS data. From the near-UV (NUV) and far-UV (FUV) magnitudes, we calculate the SFRs of the galaxies, which will further be useful for estimating the SN and KN rate. The results are compared with previous GALEX UV catalog of galaxies. There will be an updated catalog based on this catalog for calculating KN rate of the galaxies in the future work.

We have carried out ALMA observations toward the environments of G333.0162+00.7615 which was considered as a candidate of high-mass young stellar object (HMYSO) in previous studies. Our dust continuum, molecular line emission and radio recombination line emission observations show that this source is not HMYSO associated with hypercompact (HC) HII regions. Instead, we discovered two new hot cores associate with earliest stages of high mass star formation region. We estimated the rotational temperatures of these cores about 270 K from J=14→13 rotational transition of CH3CN ladder. The moment maps show velocity gradients confirming that this cores are rotating.