arXiv subjects

Ricardo Muñoz

Publications and source records attributed to Ricardo Muñoz.

6 recordsLinked to original sources

arXiv2026

Critical lengths for the linear Kadomtsev-Petviashvili II equation

The critical length phenomenon of the Korteweg-de Vries equation is well known; however, in higher dimensions, it is unknown. This work explores this property in the context of the Kadomtsev-Petviashvili equation, a two-dimensional generalization of the Korteweg-de Vries equation. Specifically, we demonstrate observability inequalities for this equation, which allow us to deduce the exact boundary controllability and boundary exponential stabilization of the linear system, provided that the spatial domain length avoids certain specific values, a direct consequence of the Paley-Wiener theorem. To the best of our knowledge, our work introduces new results by identifying a set of critical lengths for the two-dimensional Kadomtsev-Petviashvili equation.

math.AP↗

arXiv2023

Revealing the Chemical Structure of the Magellanic Clouds with APOGEE. II. Abundance Gradients of the Large Magellanic Cloud

We present the abundance gradients of the Large Magellanic Cloud (LMC) for 25 elemental abundance ratios and their respective temporal evolution as well as age-[X/Fe] trends using 6130 LMC field red giant branch (RGB) stars observed by SDSS-IV / APOGEE-2S. APOGEE is a high resolution ($R$ $\sim$22,500) $H$-band spectroscopic survey that gathered data on the LMC with broad radial and azimuthal coverage out to $\sim$10\degr. The calculated overall metallicity gradient of the LMC with no age binning is $-$0.0380 $\pm$ 0.0022 dex/kpc. We also find that many of the abundance gradients show a U-shaped trend as functions of age. This trend is marked by a flattening of the gradient but then a general steepening at more recent times. The extreme point at which all these gradients (with the U-shaped trend) begin to steepen is $\gtrsim$2 Gyr ago. In addition, some of the age-[X/Fe] trends show an increase starting a few Gyr before the extreme point in the gradient evolutions. A subset of the age-[X/Fe] trends also show maxima concurrent with the gradients' extreme points, further pinpointing a major event in the history of the LMC $\sim$2 Gyr ago. This time frame is consistent with a previously proposed interaction between the Magellanic Clouds suggesting that this is most likely the cause of the distinct trend in the gradients and age-[X/Fe] trends.

astro-ph.GA↗

arXiv2019

Variations in the width, density, and direction of the Palomar 5 tidal tails

Stars that escape globular clusters form tidal tails that are predominantly shaped by the global distribution of mass in the Galaxy, but also preserve a historical record of small-scale perturbations. Using deep $grz$ photometry from DECaLS, we present highly probable members of the tidal tails associated with the disrupting globular cluster Palomar 5. These data yield the cleanest view of a stellar stream beyond $\sim20\,\rm kpc$ and reveal: (1) a wide, low surface-brightness extension of the leading tail; (2) significant density variations along the stream; and (3) sharp changes in the direction of both the leading and the trailing tail. In the fiducial Milky Way model, a rotating bar perturbs the Palomar 5 tails and can produce streams with similar width and density profiles to those observed. However, the deviations of the stream track in this simple model do not match those observed in the Palomar 5 trailing tail, indicating the need for an additional source of perturbation. These discoveries open up the possibility of measuring the population of perturbers in the Milky Way, including dark-matter subhalos, with an ensemble of stellar streams and deep photometry alone.

astro-ph.GA↗

arXiv2018

Discovery of distant RR Lyrae stars in the Milky Way using DECam

We report the discovery of distant RR Lyrae stars, including the most distant known in the Milky Way, using data taken in the $g-$band with the Dark Energy Camera as part of the High cadence Transient Survey (HiTS; 2014 campaign). We detect a total of 173 RR Lyrae stars over a ~120 deg^2 area, including both known RR Lyrae and new detections. The heliocentric distances d_H of the full sample range from 9 to >200 kpc, with 18 of them beyond 90 kpc. We identify three sub-groups of RR Lyrae as members of known systems: the Sextans dwarf spheroidal galaxy, for which we report 46 new discoveries, and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology, we fit spherical and ellipsoidal profiles of the form rho(R) ~ R^n to the radial density distribution of RR Lyrae in the Galactic halo. The best fit corresponds to the spherical case, for which we obtain a simple power-law index of n=-4.17^{+0.18}_{-0.20}, consistent with recent studies made with samples covering shorter distances. The pulsational properties of the outermost RR Lyrae in the sample (d_H>90 kpc) differ from the ones in the halo population at closer distances. The distribution of the stars in a Period-Amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups, similar to what is found in the ultra-faint dwarf satellites around the Milky Way. The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo.

astro-ph.GA↗

arXiv2016

The High Cadence Transient Survey (HiTS) - I. Survey design and supernova shock breakout constraints

We present the first results of the High cadence Transient Survey (HiTS), a survey whose objective is to detect and follow up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera (DECam) and a custom made pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014 and 2015 campaigns we have detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting-magnitudes from our observational campaigns we measured the expected recovery fraction of randomly injected SN light curves which included SBO optical peaks produced with models from Tominaga et al. (2011) and Nakar & Sari (2010). From this analysis we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive datasets produced by astronomical observatories such as LSST.

astro-ph.SR↗

arXiv2016

Variable stars in the field of the Hydra II ultra-faint dwarf galaxy

We report the discovery of one RR Lyrae star in the ultra--faint satellite galaxy Hydra II based on time series photometry in the g, r and i bands obtained with the Dark Energy Camera at Cerro Tololo Interamerican Observatory, Chile. The RR Lyrae star has a mean magnitude of $i = 21.30\pm 0.04$ which translates to a heliocentric distance of $151\pm 8$ kpc for Hydra II; this value is $\sim 13\%$ larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of $76^{+12}_{-10}$ pc and a brighter absolute magnitude of $M_V = -5.1 \pm 0.3$, which keeps this object within the realm of the dwarf galaxies. The pulsational properties of the RR Lyrae star ($P=0.645$ d, $Δg = 0.68$ mag) suggest Hydra II may be a member of the intermediate Oosterhoff or Oosterhoff II group. A comparison with other RR Lyrae stars in ultra--faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid). However, given their magnitudes and large angular separation from Hydra II, they must be field stars not related to Hydra II.

astro-ph.GA↗