arXiv subjects

Yenifer Angarita

Publications and source records attributed to Yenifer Angarita.

3 recordsLinked to original sources

arXiv2026

A Dual-Band Centimetre Continuum Monitoring Survey of Young Stellar Objects in the Coronet Cluster

We present sensitive ($\sim$9 $μ$Jy), sub-arcsecond resolution radio continuum observations at 9.0 GHz (3.3 cm) and 14.0 GHz (2.1 cm) obtained with the Karl G. Jansky Very Large Array (VLA) toward the nearby Coronet Cluster in Corona Australis (d $\approx$ 150 pc). We monitored the region from March 2012 to February 2015 using all available VLA configurations, allowing us to construct deep X- and Ku-band maps at multiple angular resolutions. We detected 20 radio sources, including 14 previously known Young Stellar Objects (YSOs), five sources possibly associated with shock emission, and one background galaxy. We resolved IRS 5, previously known to be a binary system, and identified IRS 7A and IRS 7B as multiple systems at centimetre wavelengths. The younger Class 0 and I YSOs exhibit spectral indices $α_{pk}$ ranging from -0.4 to 1.7, while the more evolved Class II YSOs show flatter values between 0 and 0.8, consistent with free-free emission, with minor contributions from non-thermal emission. The Class III source is only constrained by an upper limit. Radio variability, measured as a fraction of the mean intensity peak, is found to be ubiquitous and independent of evolutionary stage. Variability structure functions computed for nine sources indicate no preferred timescales for most of them. We also investigate spectral index variability for six sources and find significant variations in only one object. Finally, we analyse the extended radio emission toward IRS 7B, where some subcomponents exhibit negative spectral indices suggestive of non-thermal processes.

astro-ph.GA↗

arXiv2024

Pattern Finding in mm-Wave Spectra of Massive Young Stellar Objects

Massive stars play a pivotal role in shaping their galactic surroundings due to their high luminosity and intense ionizing radiation. However, the precise mechanisms governing the formation of massive stars remain elusive. Complex organic molecules (COMs) offer an avenue for studying star formation across the low- to high-mass spectrum because COMs are found in every young stellar object phase and offer insight into the structure and temperature. We aim to unveil evolutionary patterns of COM chemistry in 41 massive young stellar objects (MYSOs) sourced from diverse catalogues, using ALMA Band 6 spectra. Previous line analysis of these sources showed the presence of CH$_3$OH, CH$_3$CN, and CH$_3$CCH with diverse excitation temperatures and column densities, indicating a possible evolutionary path across sources. However, this analysis usually involves manual line extraction and rotational diagram fitting. Here, we improve upon this process by directly retrieving the physicochemical state of MYSOs from their dimensionally-reduced spectra. We use a Locally Linear Embedding to find a lower-dimensional projection for the physicochemical parameters obtained from individual line analysis. We identify clusters of similar MYSOs in this embedded space using a Gaussian Mixture Model. We find three groups of MYSOs with distinct physicochemical conditions: i) cold, COM-poor sources, ii) warm, medium-COM-abundance sources, and iii) hot, COM-rich sources. We then apply principal component analysis (PCA) to the spectral sample, finding further evidence for an evolutionary path across MYSO groups. Finally, we find that the physicochemical state of our sample can be derived directly from the spectra by training a simple random forest model on the first few PCA components. Our results highlight the effectiveness of dimensionality reduction in obtaining clear physical insights directly from MYSO spectra.

astro-ph.GA↗

arXiv2023

Tomographic Imaging of the Sagittarius Spiral Arm's Magnetic Field Structure

The Galactic global magnetic field is thought to play a vital role in shaping Galactic structures such as spiral arms and giant molecular clouds. However, our knowledge of magnetic field structures in the Galactic plane at different distances is limited, as measurements used to map the magnetic field are the integrated effect along the line of sight. In this study, we present the first-ever tomographic imaging of magnetic field structures in a Galactic spiral arm. Using optical stellar polarimetry over a $17' \times 10'$ field of view, we probe the Sagittarius spiral arm. Combining these data with stellar distances from the $Gaia$ mission, we can isolate the contributions of five individual clouds along the line of sight by analyzing the polarimetry data as a function of distance. The observed clouds include a foreground cloud ($d < 200$ pc) and four clouds in the Sagittarius arm at 1.23 kpc, 1.47 kpc, 1.63 kpc, and 2.23 kpc. The column densities of these clouds range from 0.5 to $2.8 \times 10^{21}~\mathrm{cm}^{-2}$. The magnetic fields associated with each cloud show smooth spatial distributions within their observed regions on scales smaller than 10 pc and display distinct orientations. The position angles projected on the plane-of-sky, measured from the Galactic north to east, for the clouds in increasing order of distance are $135^\circ$, $46^\circ$, $58^\circ$, $150^\circ$, and $40^\circ$, with uncertainties of a few degrees. Notably, these position angles deviate significantly from the direction parallel to the Galactic plane.

astro-ph.GA↗