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O. Morata

Publications and source records attributed to O. Morata.

At least 19 recordsLinked to original sources

{\sc ampere}: A tool to fit heterogeneous observations consistently

As astronomy advances and data becomes more complex, models and inference also become more expensive and complex. In this paper we present {\sc ampere}, which aims to solve this problem using modern inference techniques such as flexible likelihood functions and likelihood-free inference. {\sc ampere}\ can be used to do Bayesian inference even with very expensive models (hours of CPU time per model) that do not include all the features of the observations (e.g. missing lines, incomplete descriptions of PSFs, etc). We demonstrate the power of \ampere\ using a number of simple models, including inferring the posterior mineralogy of circumstellar dust using a Monte Carlo Radiative Transfer model. {\sc ampere}\ reproduces the input parameters well in all cases, and shows that some past studies have tended to underestimate the uncertainties that should be attached to the parameters. {\sc ampere}\ can be applied to a wide range of problems, and is particularly well-suited to using expensive models to interpret data.

astro-ph.IM

First detection of variable radio emission originating from the infant planetary system V1298 Tau

V1298 Tau is a very young and magnetically active star which hosts a benchmark multi-planetary system to study planet formation and evolutionary history at the earliest stages. We selected V1298 Tau for a first targeted follow-up at radio frequencies with the Karl G. Jansky Very Large Telescope (JVLA), the upgraded Giant Metrewave Radio Telescope (uGMRT), and the Sardinia Radio Telescope (SRT), to search for emission in the overall frequency range 0.55-7.2 GHz. Detecting radio emission from such a very active star is key to characterise its magnetosphere, allowing in principle to probe the strength of the coronal magnetic field and plasma density. Observations were carried out between Oct 2023 and Sept 2024: three epochs with uGMRT band-4 (0.55-0.75 GHz), 12 epochs with the JVLA using L (1-2 GHz) and C (4.5-6.5 GHz) bands, and three epochs with SRT using C-high band (6-7.2 GHz). We report the first detection of radio emission from V1298 Tau at different epochs using the JVLA. The emission has maximum peak flux densities of 91$\pm$10 and 177$\pm$6 $\mu$Jy/beam in the L- and C-band, respectively. From a comparison with contemporary optical photometry, we found that the detected emission with the highest fluxes are located around a phase of minimum of the photospheric light curve. Although the uGMRT and SRT observations could not detect the source, we measured 3$\sigma$ flux density upper limits in the range ~41-56 $\mu$Jy/beam using uGMRT, while with SRT we reached upper limits down to 13 mJy. The lack of a significant fraction of circular polarisation indicates that the observed flux is not due to electron cyclotron maser emission from star-planet interaction, and it is likely produced by gyrosynchroton/cyclotron emission from the corona triggered by stellar magnetic activity, although we cannot exclude thermal emission due to a lack of constraints on the brightness temperature.

astro-ph.EP

Substellar candidates at the earliest stages: the SUCANES database

Brown dwarfs are the bridge between low-mass stars and giant planets. One way of shedding light on their dominant formation mechanism is to study them at the earliest stages of their evolution, when they are deeply embedded in their parental clouds. Several works have identified pre- and proto-brown dwarfs candidates using different observational approaches. The aim of this work is to create a database with all the objects classified as very young substellar candidates in the litearature in order to study them in an homogeneous way. We have gathered all the information about very young substellar candidates available in the literature until 2020. We have retrieved their published photometry from the optical to the centimeter regime, and we have written our own codes to derive their bolometric temperatures and luminosities, and their internal luminosities. We have also populated the database with other parameters extracted from the literature, like e.g. the envelope masses, their detection in some molecular species, and presence of outflows. The result of our search is the SUCANES database, containing 174 objects classified as potential very young substellar candidates in the literature. We present an analysis of the main properties of the retrieved objects. Since we have updated the distances to several star forming regions, this has allowed us to reject some candidates based on their internal luminosities. We have also discussed the derived physical parameters and envelope masses for the best substellar candidates isolated in SUCANES. As an example of a scientific exploitation of this database, we present a feasibility study for the detection of radiojets with upcoming facilities: the ngVLA and the SKA interferometers. The SUCANES database is accessible through a Graphical User Interface and it is open to any potential user.

astro-ph.SR

CHIMPS2: Survey description and $^{12}$CO emission in the Galactic Centre

The latest generation of Galactic-plane surveys is enhancing our ability to study the effects of galactic environment upon the process of star formation. We present the first data from CO Heterodyne Inner Milky Way Plane Survey 2 (CHIMPS2). CHIMPS2 is a survey that will observe the Inner Galaxy, the Central Molecular Zone (CMZ), and a section of the Outer Galaxy in $^{12}$CO, $^{13}$CO, and C$^{18}$O $(J = 3\rightarrow2)$ emission with the Heterodyne Array Receiver Program on the James Clerk Maxwell Telescope (JCMT). The first CHIMPS2 data presented here are a first look towards the CMZ in $^{12}$CO J = 3$\rightarrow$2 and cover $-3^{\circ}\leq\,\ell\,\leq\,5^{\circ}$ and $\mid$b$\mid \leq 0.5^{\circ}$ with angular resolution of 15 arcsec, velocity resolution of 1 km s$^{-1}$, and rms $ΔT_A ^\ast =$ 0.58 K at these resolutions. Such high-resolution observations of the CMZ will be a valuable data set for future studies, whilst complementing the existing Galactic Plane surveys, such as SEDIGISM, the Herschel infrared Galactic Plane Survey, and ATLASGAL. In this paper, we discuss the survey plan, the current observations and data, as well as presenting position-position maps of the region. The position-velocity maps detect foreground spiral arms in both absorption and emission.

astro-ph.GA

ALMA Observations of HCO+ and HCN Emission in a massive star forming region N55 of the Large Magellanic Cloud

We present the results of high spatial resolution HCO$^{+}$($1-0$) and HCN($1-0$) observations of N55 south region (N55-S) in the Large Magellanic Cloud (LMC), obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). N55-S is a relatively less extreme star-forming region of the LMC characterized by a low radiation field. We carried out a detailed analysis of the molecular emission to investigate the relation between dense molecular clumps and star formation in the quiescent environment of N55-S. We detect ten molecular clumps with significant HCO$^{+}(1-0)$ emission and eight with significant HCN($1-0$) emission, and estimate the molecular clump masses by virial and local thermodynamic equilibrium analysis. All identified young stellar objects (YSOs) in the N55-S are found to be near the HCO$^{+}$ and HCN emission peaks showing the association of these clumps with recent star formation activity. The molecular clumps that have associated YSOs show relatively larger linewidths and masses than those without YSOs. We compare the clump properties of the N55-S with those of other giant molecular clouds (GMCs) in the LMC and find that N55-S clumps possess similar size but relatively lower linewidth and larger HCN/HCO$^{+}$(1$-$0) flux ratio. These results can be attributed to the low radiation field in N55-S resulted by relatively low star formation activity compared to other active star-forming regions like 30Doradus-10 and N159. The dense gas fraction of N55-S is $\sim$ 0.025, lower compared to other GMCs of the LMC supporting the low star formation efficiency of this region.

astro-ph.GA

ALMA reveals molecular cloud N55 in the Large Magellanic Cloud as a site of massive star formation

We present the molecular cloud properties of N55 in the Large Magellanic Cloud using $^{12}$CO(1-0) and $^{13}$CO(1-0) observations obtained with Atacama Large Millimeter Array. We have done a detailed study of molecular gas properties, to understand how the cloud properties of N55 differ from Galactic clouds. Most CO emission appears clumpy in N55, and molecular cores that have YSOs show larger linewidths and masses. The massive clumps are associated with high and intermediate mass YSOs. The clump masses are determined by local thermodynamic equilibrium and virial analysis of the $^{12}$CO and $^{13}$CO emissions. These mass estimates lead to the conclusion that, (a) the clumps are in self-gravitational virial equilibrium, and (b) the $^{12}$CO(1-0)-to-H$_2$ conversion factor, X$_{\rm CO}$, is 6.5$\times$10$^{20}$cm$^{-2}$(K km s$^{-1}$)$^{-1}$. This CO-to-H$_2$ conversion factor for N55 clumps is measured at a spatial scale of $\sim$0.67 pc, which is about two times higher than the X$_{\rm CO}$ value of Orion cloud at a similar spatial scale. The core mass function of N55 clearly show a turnover below 200M$_{\odot}$, separating the low-mass end from the high-mass end. The low-mass end of the $^{12}$CO mass spectrum is fitted with a power law of index 0.5$\pm$0.1, while for $^{13}$CO it is fitted with a power law index 0.6$\pm$0.2. In the high-mass end, the core mass spectrum is fitted with a power index of 2.0$\pm$0.3 for $^{12}$CO, and with 2.5$\pm$0.4 for $^{13}$CO. This power-law behavior of the core mass function in N55 is consistent with many Galactic clouds.

astro-ph.GA

Early phases in the stellar and substellar formation and evolution: Infrared and submillimeter data in the Barnard 30 dark cloud

The early evolutionary stage of brown dwarfs are not very well characterized, specially during the embedded phase. To gain insight into the dominant formation mechanism of very low-mass objects and brown dwarfs, we conducted deep observations at 870$μ$m with the LABOCA bolometer at the APEX telescope. Our goal was to identify young sub-mm sources in the Barnard 30 dark cloud. We complemented these data with multi-wavelength observations from the optical to the far-IR and. As a result, we have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified in three distinct groups. First, 15 out of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BDs candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include brown dwarf candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 $μ$m, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects (YSOs), eight proto-BD candidates (with another three dubious cases), and one Very Low Luminosity object (VeLLO).

astro-ph.SR

A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

In this work we present ALMA continuum observations at 880 $μ$m of 30 sub-mm cores previously identified with APEX/LABOCA at 870$μ$m in the Barnard 30 cloud. The main goal is to characterize the youngest and lowest mass population in the cloud. As a result, we report the detection of five (out of 30) spatially unresolved sources with ALMA, with estimated masses between 0.9 and 67 M$_{\rm Jup}$. From these five sources, only two show gas emission. The analysis of multi-wavelength photometry from these two objects, namely B30-LB14 and B30-LB19, is consistent with one Class II- and one Class I low-mass stellar object, respectively. The gas emission is consistent with a rotating disk in the case of B30-LB14, and with an oblate rotating envelope with infall signatures in the case of LB19. The remaining three ALMA detections do not have infrared counterparts and can be classified as either deeply embedded objects or as starless cores if B30 members. In the former case, two of them (LB08 and LB31) show internal luminosity upper limits consistent with Very Low Luminosity objects, while we do not have enough information for LB10. In the starless core scenario, and taking into account the estimated masses from ALMA and the APEX/LABOCA cores, we estimate final masses for the central objects in the substellar domain, so they could be classified as pre-BD core candidates.

astro-ph.GA

Constraints on the circumstellar dust around KIC 8462852

We present millimetre (SMA) and sub-millimetre (SCUBA-2) continuum observations of the peculiar star KIC 8462852 which displayed several deep and aperiodic dips in brightness during the Kepler mission. Our observations are approximately confusion-limited at 850 $μ$m and are the deepest millimetre and sub-millimetre photometry of the star that has yet been carried out. No significant emission is detected towards KIC 8462852. We determine upper limits for dust between a few 10$^{-6}$ M$_{\oplus}$ and 10$^{-3}$ M$_{\oplus}$ for regions identified as the most likely to host occluding dust clumps and a total overall dust budget of $<$7.7 M$_{\oplus}$ within a radius of 200 AU. Such low limits for the inner system make the catastrophic planetary disruption hypothesis unlikely. Integrating over the Kepler lightcurve we determine that at least 10$^{-9}$ M$_{\oplus}$ of dust is required to cause the observed Q16 dip. This is consistent with the currently most favoured cometary breakup hypothesis, but nevertheless implies the complete breakup of $\sim$ 30 Comet 1/P Halley type objects. Finally, in the wide SCUBA-2 field-of-view we identify another candidate debris disc system that is potentially the largest yet discovered.

astro-ph.SR

A submillimeter search for pre- and proto-brown dwarfs in Chamaeleon II

Context. Chamaeleon II molecular cloud is an active star forming region that offers an excellent opportunity for studying the formation of brown dwarfs in the southern hemisphere. Aims. Our aims are to identify a population of pre- and proto- brown dwarfs (5 sigma mass limit threshold of ~0.015 Msun) and provide information on the formation mechanisms of substellar objects. Methods. We performed high sensitivity observations at 870 microns using the LABOCA bolometer at the APEX telescope towards an active star forming region in Chamaeleon II. The data are complemented with an extensive multiwavelength catalogue of sources from the optical to the far-infrared to study the nature of the LABOCA detections. Results. We detect fifteen cores at 870 microns, and eleven of them show masses in the substellar regime. The most intense objects in the surveyed field correspond to the submillimeter counterparts of the well known young stellar objects DK Cha and IRAS 12500-7658. We identify a possible proto-brown dwarf candidate (ChaII-APEX-L) with IRAC emission at 3.6 and 4.5 microns. Conclusions. Our analysis indicates that most of the spatially resolved cores are transient, and that the point-like starless cores in the sub-stellar regime (with masses between 0.016 Msun and 0.066 Msun) could be pre-brown dwarfs cores gravitationally unstable if they have radii smaller than 220 AU to 907 AU (1.2" to 5" at 178 pc) respectively for different masses. ALMA observations will be the key to reveal the energetic state of these pre-brown dwarfs candidates.

astro-ph.SR

The Spanish Square Kilometre Array White Book

The Square Kilometre Array (SKA) is called to revolutionise essentially all areas of Astrophysics. With a collecting area of about a square kilometre, the SKA will be a transformational instrument, and its scientific potential will go beyond the interests of astronomers. Its technological challenges and huge cost requires a multinational effort, and Europe has recognised this by putting the SKA on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI). The Spanish SKA White Book is the result of the coordinated effort of 120 astronomers from 40 different research centers. The book shows the enormous scientific interest of the Spanish astronomical community in the SKA and warrants an optimum scientific exploitation of the SKA by Spanish researchers, if Spain enters the SKA project.

astro-ph.IM

First detection of thermal radio jets in a sample of proto-brown dwarf candidates

We observed with the JVLA at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf candidates in Taurus in a search for thermal radio jets driven by the most embedded brown dwarfs. We detected for the first time four thermal radio jets in proto-brown dwarf candidates. We compiled data from UKIDSS, 2MASS, Spitzer, WISE and Herschel to build the Spectral Energy Distribution (SED) of the objects in our sample, which are similar to typical Class~I SEDs of Young Stellar Objects (YSOs). The four proto-brown dwarf candidates driving thermal radio jets also roughly follow the well-known trend of centimeter luminosity against bolometric luminosity determined for YSOs, assuming they belong to Taurus, although they present some excess of radio emission compared to the known relation for YSOs. Nonetheless, we are able to reproduce the flux densities of the radio jets modeling the centimeter emission of the thermal radio jets using the same type of models applied to YSOs, but with corresponding smaller stellar wind velocities and mass-loss rates, and exploring different possible geometries of the wind or outflow from the star. Moreover, we also find that the modeled mass outflow rates for the bolometric luminosities of our objects agree reasonably well with the trends found between the mass outflow rates and bolometric luminosities of YSOs, which indicates that, despite the "excess" centimeter emission, the intrinsic properties of proto-brown dwarfs are consistent with a continuation of those of very low mass stars to a lower mass range. Overall, our study favors the formation of brown dwarfs as a scaled-down version of low-mass stars.

astro-ph.GA

The Science Cases for Building a Band 1 Receiver Suite for ALMA

We present the various science cases for building Band 1 receivers as part of ALMA's ongoing Development Program. We describe the new frequency range for Band 1 of 35-52 GHz, a range chosen to maximize the receiver suite's scientific impact. We first describe two key science drivers: 1) the evolution of grains in protoplanetary disks and debris disks, and 2) molecular gas in galaxies during the era of re-ionization. Studies of these topics with Band 1 receivers will significantly expand ALMA's Level 1 Science Goals. In addition, we describe a host of other exciting continuum and line science cases that require ALMA's high sensitivity and angular resolution. For example, ALMA Band 1 continuum data will probe the Sunyaev-Zel'dovich Effect in galaxy clusters, Very Small Grains and spinning dust, ionized jets from young stars, spatial and flaring studies of Sgr A*, the acceleration sites of solar flares, pulsar wind nebulae, radio supernovae, and X-ray binaries. Furthermore, ALMA Band 1 line data will probe chemical differentiation in cloud cores, complex carbon chain molecules, extragalactic radio recombination lines, masers, magnetic fields through Zeeman effect measurements, molecular outflows from young stars, the co-evolution of star formation and active galactic nuclei, and the molecular content of galaxies at z ~ 3. ALMA provides similar to better sensitivities than the JVLA over 35-50 GHz, with differences increasing with frequency. ALMA's smaller antennas and shorter baselines, greater number of baselines, and single-dish capabilities, however, give it a significant edge for observing extended emission, making wide-field maps (mosaics), or attaining high image fidelity, as required by the described science cases.

astro-ph.IM

Millimetric and sub-millimetric observations of IRAS 05327+3404 "Holoea" in M36

The transition between the proto-star, Class I, and the pre-main sequence star, Class II, phases is still one of the most uncertain, and important, stages in the knowledge of the process of formation of an individual star, because it is the stage that determines the final mass of the star. We observed the YSO "Holoea", associated with IRAS 05327+3404, which was classified as an object in transition between the Class I and Class II phases with several unusual properties, and appears to be surrounded by large amounts of circumstellar material. We used the SMA and BIMA telescopes at millimeter and sub-millimeter wavelengths to observe the dust continuum emission and the CO (1-0) and (2-1), HCO+ (1-0) and (3-2), and HCN (1-0) transitions in the region around IRAS 05327+3404. We detected two continuum emission peaks at 1.1-mm: SMM 1, the sub-mm counterpart of IRAS 05327+3404, and SMM 2, ~6 arcsec to the West. The emissions of the three molecules show marked differences. The CO emission near the systemic velocity is filtered out by the telescopes, and CO mostly traces the high-velocity gas. The HCO+ and HCN emissions are more centrally concentrated around the central parts of the region, and show several intensity peaks coincident with the sub-mm continuum peaks. We identify two main molecular outflows: a bipolar outflow in an E-W direction that would be powered by SMM 1 and another one in a NE direction, which we associate with SMM 2. We propose that the SMM sources are probably Class I objects, with SMM 1 in an earlier evolutionary stage.

astro-ph.GA

Young starless cores embedded in the magnetically dominated Pipe Nebula. II. Extended dataset

The Pipe nebula is a massive, nearby, filamentary dark molecular cloud with a low star-formation efficiency threaded by a uniform magnetic field perpendicular to its main axis. It harbors more than a hundred, mostly quiescent, very chemically young starless cores. The cloud is, therefore, a good laboratory to study the earliest stages of the star-formation process. We aim to investigate the primordial conditions and the relation among physical, chemical, and magnetic properties in the evolution of low-mass starless cores. We used the IRAM 30-m telescope to map the 1.2 mm dust continuum emission of five new starless cores, which are in good agreement with previous visual extinction maps. For the sample of nine cores, which includes the four cores studied in a previous work, we derived a Av to NH2 factor of (1.27$\pm$0.12)$\times10^{-21}$ mag cm$^{2}$ and a background visual extinction of ~6.7 mag possibly arising from the cloud material. We derived an average core diameter of ~0.08 pc, density of ~10$^5$ cm$^{-3}$, and mass of ~1.7 Msun. Several trends seem to exist related to increasing core density: (i) diameter seems to shrink, (ii) mass seems to increase, and (iii) chemistry tends to be richer. No correlation is found between the direction of the surrounding diffuse medium magnetic field and the projected orientation of the cores, suggesting that large scale magnetic fields seem to play a secondary role in shaping the cores. The full abstract is available in the pdf.

astro-ph.GA

Observing a column-dependent zeta in dense interstellar sources: the case of the Horsehead Nebula

Context: Observations of small carbon-bearing molecules such as CCH, C4H, c-C3H2, and HCO in the Horsehead Nebula have shown these species to have higher abundances towards the edge of the source than towards the center. Aims: Given the determination of a wide range of values for zeta (s-1), the total ionization rate of hydrogen atoms, and the proposal of a column-dependent zeta(N_H), where N_H is the total column of hydrogen nuclei, we desire to determine if the effects of zeta(N_H) in a single object with spatial variation can be observable. We chose the Horsehead Nebula because of its geometry and high density. Method: We model the Horsehead Nebula as a near edge-on photon dominated region (PDR), using several choices for zeta, both constant and as a function of column. The column-dependent zeta functions are determined by a Monte Carlo model of cosmic ray penetration, using a steep power-law spectrum and accounting for ionization and magnetic field effects. We consider a case with low-metal elemental abundances as well as a sulfur-rich case. Results: We show that use of a column-dependent zeta(N_H) of 5(-15) s-1 at the surface and 7.5(-16) s-1 at Av = 10 on balance improves agreement between measured and theoretical molecular abundances, compared with constant values of zeta.

astro-ph.GA

Water maser detections in southern candidates to post-AGB stars and Planetary Nebulae

We intended to study the incidence and characteristics of water masers in the envelopes of stars in the post-AGB and PN evolutionary stages. We have used the 64-m antenna in Parkes (Australia) to search for water maser emission at 22 GHz, towards a sample of 74 sources with IRAS colours characteristic of post-AGB stars and PNe, at declination $< -32 °$. In our sample, 39% of the sources are PNe or PNe candidates, and 50% are post-AGB stars or post-AGB candidates. We have detected four new water masers, all of them in optically obscured sources: three in PNe candidates (IRAS 12405-6219, IRAS 15103-5754, and IRAS 16333-4807); and one in a post-AGB candidate (IRAS 13500-6106). The PN candidate IRAS 15103-5754 has water fountain characteristics, and it could be the first PN of this class found. We confirm the tendency suggested in Paper I that the presence of water masers in the post-AGB phase is favoured in obscured sources with massive envelopes. We propose an evolutionary scenario for water masers in the post-AGB and PNe stages, in which ``water fountain'' masers could develop during post-AGB and early PN stages. Later PNe would show lower velocity maser emission, both along jets and close to the central objects, with only the central masers remaining in more evolved PNe.

astro-ph.SR

Radio Astronomy Data Model for Single-Dish Multiple-Feed Telescopes, and Robledo Archive Architecture

All the effort that the astrophysical community has put into the development of the Virtual Observatory (VO) has surpassed the non-return point: the VO is a reality today, and an initiative that will self-sustain, and to which all archival projects must adhere. We have started the design of the scientific archive for the DSS-63 70-m antenna at NASA's DSN station in Robledo de Chavela (Madrid). Here we show how we can use all VO proposed data models to build a VO-compliant single-dish, multiple-feed, radio astronomical archive data model (RADAMS) suitable for the archival needs of the antenna. We also propose an exhaustive list of Universal Content Descriptors (UCDs) and FITS keywords for all relevant metadata. We will further refine this data model with the experience that we will gain from that implementation.

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