Related papers: Southern massive stars at high angular resolution.…
This thesis focuses on the statistical properties of wide binary (WB) star systems in the Galactic field. For the present study we select a homogeneous sample covering about 675 square degrees in the direction of the NGP. It contains nearly…
Imaging the bright maser emission produced by several molecular species at centimeter wavelengths is an essential tool for understanding the process of massive star formation because it provides a way to probe the kinematics of dense…
We present and release the full dataset for the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. This survey used the Submillimeter Array (SMA) to image the 74 known protostars within the Perseus molecular…
A galaxy's stellar mass is one of its most fundamental properties, but it remains challenging to measure reliably. With the advent of very large optical spectroscopic surveys, efficient methods that can make use of low signal-to-noise…
Young, intermediate-mass stars are experiencing renewed interest as targets for direct-imaging planet searches. However, these types of stars are part of multiple systems more often than not. Close stellar companions affect the formation…
Known bright S stars, recognized as such by their enhanced s-process abundances and C/O ratio, are typically members of the asymptotic giant branch (AGB) or the red giant branch (RGB). Few modern digital spectra for these objects have been…
Asteroseismology, i.e. the study of the internal structures of stars via their global oscillations, is a valuable tool to obtain stellar parameters such as mass, radius, surface gravity and mean density. These parameters can be obtained…
Using precise galaxy stellar mass function measurements in the COSMOS field we determine the stellar-to-halo mass relationship (SHMR) using a parametric abundance matching technique. The unique combination of size and highly complete…
Modern large-scale photometric surveys have provided us with multi-band photometries of billions of stars. Determining the stellar atmospheric parameters, such as the effective temperature (\teff) and metallicities (\feh), absolute…
In this empirical work, we aim to quantify the systematic uncertainties in stellar mass $(M_\star)$ estimates made from spectral energy distribution (SED) fitting through stellar population synthesis (SPS), for galaxies in the local…
Using a combination of radio and optical imaging at 0.1\arcs to 0.2\arcs resolution with the VLA/MERLIN and HST has led to a breakthrough in our understanding of radio emission from distant (0.1<z<3) starburst galaxies. We have recently…
We measure the merger fraction of massive galaxies using the UltraVISTA/COSMOS $Ks$-band selected catalog, complemented with the deeper, higher resolution 3DHST+CANDELS catalog selected in the HST/WFC3 $H$-band, presenting the largest…
Accurate determinations of atmospheric parameters (effective temperature $T_{\rm eff}$, surface gravity log $g$ and metallicity [Fe/H]) and distances for large complete samples are of vital importance for various Galactic studies. We have…
We examine the possibility that very massive stars greatly exceeding the commonly adopted stellar mass limit of 150 Msun may be present in young star clusters in the local universe. We identify ten candidate clusters, some of which may host…
Galaxy pairs with separations of only a few kpc represent important stages in the merger-driven growth of supermassive black holes (SMBHs). However, such mergers are difficult to identify observationally due to the correspondingly small…
Massive stars exhibit a perplexing mismatch between their inferred masses from different observational techniques, posing a significant challenge to our understanding of stellar evolution and structure. This discrepancy is believed to be…
We study the statistical properties of the wide binary population in the Galaxy field with projected separations larger than 200 AU by constructing the stellar angular two-point correlation function (2PCF) from a homogeneous sample of…
We present the results of a direct-imaging survey for very large separation ($>$100 au), companions around 95 nearby young K5-L5 stars and brown dwarfs. They are high-likelihood candidates or confirmed members of the young ($\lessapprox$150…
Context. The "mass discrepancy" in massive O stars represents a long-standing problem in stellar astrophysics with far-reaching implications for the chemical and dynamical feedback in galaxies. Aims. Our goal is to investigate this mass…
We use two-dimensional kinematic maps of simulated binary disc mergers to investigate the $\lambda_R$-parameter, which is a luminosity weighted measure of projected angular momentum per unit mass. This parameter was introduced to subdivide…