Calibration of evolutionary diagnostics in high-mass star formation

The evolutionary classification of massive clumps that are candidate progenitors of high-mass young stars and clusters relies on a variety of independent diagnostics based on observables from the near-infrared to the radio. A promising evolutionary indicator for massive and dense cluster-progenitor clumps is the L/M ratio between the bolometric luminosity and the mass of the clumps. With the aim of providing a quantitative calibration for this indicator we used SEPIA/APEX to obtain CH3C2H(12-11) observations, that is an excellent thermometer molecule probing densities > 10^5 cm^-3 , toward 51 dense clumps with M>1000 solar masses, and uniformly spanning -2 < Log(L/M) < 2.3. We identify three distinct ranges of L/M that can be associated to three distinct phases of star formation in massive clumps. For L/M <1 no clump is detected in CH3C2H , suggesting an inner envelope temperature below 30K. For 1< L/M < 10 we detect 58% of the clumps, with a temperature between 30 and 35 K independently from the exact value of L/M; such clumps are building up luminosity due to the formation of stars, but no star is yet able to significantly heat the inner clump regions. For L/M> 10 we detect all the clumps, with a gas temperature rising with Log(L/M), marking the appearance of a qualitatively different heating source within the clumps; such values are found towards clumps with UCHII counterparts, suggesting that the quantitative difference in T - L/M behaviour above L/M >10 is due to the first appearance of ZAMS stars in the clumps.Comment: Astrophysical Journal Letters, Accepte

Physical characteristics of G331.5-0.1: The luminous central region of a Giant Molecular Cloud

We report molecular line and dust continuum observations toward the high-mass star forming region G331.5-0.1, one of the most luminous regions of massive star-formation in the Milky Way, located at the tangent region of the Norma spiral arm, at a distance of 7.5 kpc. Molecular emission was mapped toward the G331.5-0.1 GMC in the CO (J=1-0) and C18O (J=1-0) lines with NANTEN, while its central region was mapped in CS (J=2-1 and J=5-4) with SEST, and in CS (J=7-6) and 13CO (J=3-2) with ASTE. Continuum emission mapped at 1.2 mm with SIMBA and at 0.87 mm with LABOCA reveal the presence of six compact and luminous dust clumps, making this source one of the most densely populated central regions of a GMC in the Galaxy. The dust clumps are associated with molecular gas and they have the following average properties: size of 1.6 pc, mass of 3.2x10^3 Msun, molecular hydrogen density of 3.7x10^4 cm^{-3}, dust temperature of 32 K, and integrated luminosity of 5.7x10^5 Lsun, consistent with values found toward other massive star forming dust clumps. The CS and 13CO spectra show the presence of two velocity components: a high-velocity component at ~ -89 km s^{-1}, seen toward four of the clumps, and a low-velocity component at ~ -101 km s^{-1} seen toward the other two clumps. Radio continuum emission is present toward four of the molecular clumps, with spectral index estimated for two of them of 0.8+-0.2 and 1.2+-0.2. A high-velocity molecular outflow is found at the center of the brightest clump, with a line width of 26 km s^{-1} (FWHM) in CS (J=7-6). Observations of SiO (J=7-6 and J=8-7), and SO (J_K=8_8-7_7 and J_K=8_7-7_6) lines provide estimates of the gas rotational temperature toward this outflow >120 K and >75 K, respectively.Comment: 34 pages, 20 figures, 11 tables, Accepted for Publication in The Astrophysical Journa

Pruebas de viabilidad para aplicaciones espaciales sobre filtros de microondas implementados en tecnologías de transmisión integradas en sustrato

[ES] El continuo avance de los sistemas de comunicaciones, así como de las tecnologías asociadas a los mismos hace que sea necesario el desarrollo de estudios que permitan avalar el correcto funcionamiento de los subsistemas de comunicaciones bajo circunstancias nunca antes vistas. En concreto, el creciente uso de pico y nano satélites dentro de la industria espacial insta al proceso de diseño de dispositivos que vayan a ser embarcados en misiones de índole espacial a tener en cuenta los efectos adversos asociados a este tipo de entornos. Este proyecto presenta un estudio completo de todos aquellos fenómenos físicos a tener en cuenta a la hora de realizar misiones espaciales con el fin de demostrar la viabilidad de cuatro filtros de microondas en banda Ku fabricados y medidos expresamente para este trabajo e implementados en cuatro tecnologías planares distintas (SIW, ESIW, ADSIW y ESICL). Estos filtros serán sometidos a análisis para estudiar su comportamiento ante fenómenos de descarga de electrones, fenómenos de expansión y contracción térmica, así como para estudiar su resistencia mecánica ante elevados niveles de estrés mecánico.[EN] The continuous progress of communication systems, as well as the technologies that are associated with them makes it necessary to develop studies that allow us to endorse the correct functioning of the communication subsystems under circumstances never previously seen. In particular, the increasing use of pico and nano satellites within the spatial industry urges the process of designing devices, which will be embarked on spatial missions, to take into account the adverse effects that are associated with this type of environments. This project presents a complete study of all those physical phenomena to have into account when carrying out space missions in order to demonstrate the feasibility of four specifically manufactured and measured Ku-band microwave filters that have been implemented in four different planar technologies (SIW, ESIW, ADSIW and ESICL) for this work. These filters will be analyzed to study their behavior in front of electron discharge phenomena, thermal expansion and contraction phenomena, as well as to study their mechanical resistance to high levels of mechanical stress.Merello Giménez, JM. (2020). Pruebas de viabilidad para aplicaciones espaciales sobre filtros de microondas implementados en tecnologías de transmisión integradas en sustrato. Universitat Politècnia de València. http://hdl.handle.net/10251/157705TFG

Desarrollo de dispositivos pasivos de microondas en tecnología ESICL

The continuous advance of both the technology and the communications systems, as well as the current competition in this sector, makes necessary the use of high performance and cheap transmission lines of simple manufacture. This project focuses on the implementation of passive devices (a 90º hybrid directional coupler and a T-splitter) at microwave frequencies over the e¿cient and novel guiding technology Empty Substrate Integrated Coaxial Line. In this way, a complete study of all the phases involved in the manufacturing process (theoretical analysis, design, optimization, manufacturing and measurement) of an electronic device has been carried out and, subsequently, implemented with the two devices mentioned above.El continuo avance de la tecnología y, en consecuencia, de los sistemas de comunicaciones, así como la gran competencia presente en este sector, hace necesario el uso de líneas de transmisión de altas prestaciones, baratas y de simple fabricación. Este proyecto se enfoca en la implementación de dispositivos pasivos (un acoplador direccional híbrido de 90º y un divisor en T) a frecuencias de microondas sobre la e¿ciente y novedosa tecnología de guiado Empty Substrate Integrated Coaxial Line. De este modo, se ha llevado a cabo un estudio completo de todas las fases implicadas en el proceso de fabricación (análisis teórico, diseño, optimización, fabricación y medición de resultados) de un dispositivo electrónico para, posteriormente, llevarlas a la práctica con la fabricación, sobre tecnología planar, de los dos dispositivos antes mencionados.Merello Giménez, JM. (2017). Desarrollo de dispositivos pasivos de microondas en tecnología ESICL. http://hdl.handle.net/10251/91759TFG

The Bolocam Galactic Plane Survey. XI. Temperatures and Substructure of Galactic Clumps Based on 350 ?M Observations

We present 107 maps of continuum emission at 350 mu m from Galactic molecular clumps. Observed sources were mainly selected from the Bolocam Galactic Plane Survey (BGPS) catalog, with three additional maps covering star-forming regions in the outer Galaxy. The higher resolution of the SHARC-II images (8."5 beam) compared with the 1.1 mm images from BGPS (33"beam) allowed us to identify a large population of smaller substructures within the clumps. A catalog is presented for the 1386 sources extracted from the 350 mu m maps. The color temperature distribution of clumps based on the two wavelengths has a median of 13.3 K and mean of 16.3 +/- 0.4 K, assuming an opacity law index of 1.7. For the structures with good determination of color temperatures, the mean ratio of gas temperature, determined from NH3 observations, to dust color temperature is 0.88 and the median ratio is 0.76. About half the clumps have more than 2 substructures and 22 clumps have more than 10. The fraction of the mass in dense substructures seen at 350 mu m compared to the mass of their parental clump is similar to 0.19, and the surface densities of these substructures are, on average, 2.2 times those seen in the clumps identified at 1.1 mm. For a well-characterized sample, 88 structures (31%) exceed a surface density of 0.2 g cm(-2), and 18 (6%) exceed 1.0 g cm(-2), thresholds for massive star Formation suggested by theorists.National Science Foundation through NSF grant AST-0708403NRAONSF AST-9980846, AST-0206158, AST-1109116Fulbright FellowshipASI, AgenziaSpaziale Italiana I/038/080/0, I/029/12/0national funding agency: CSA (Canada)national funding agency: NAOC (China)national funding agency: CEA (France)national funding agency: ASI (Italy)national funding agency: MCINN (Spain)national funding agency: Stockholm Observatory (Sweden)national funding agency: STFC (UK)national funding agency: NASA (USA)national funding agency: CNES (France)national funding agency: CNRS (France)Astronom

ALMA observations of the massive molecular outflow G331.512-0.103

The object of this study is one of the most energetic and luminous molecular outflows known in the Galaxy, G331.512-0.103. Observations with ALMA Band 7 (350 GHz; 0.86 mm) reveal a very compact, extremely young bipolar outflow and a more symmetric outflowing shocked shell surrounding a very small region of ionized gas. The velocities of the bipolar outflow are about 70 km s^{-1} on either side of the systemic velocity. The expansion velocity of the shocked shell is ~24 km s^{-1}, implying a crossing time of about 2000 yrs. Along the symmetry axis of the outflow, there is a velocity feature, which could be a molecular "bullet" of high-velocity dense material. The source is one of the youngest examples of massive molecular outflow found associated with a high-mass star.Comment: 9 pages, 4 figures, 1 table, Accepted for publication in The Astrophysical Journal Letters, small typos correcte

Observations and chemical modeling of the isotopologues of formaldehyde and the cations of formyl and protonated formaldehyde in the hot molecular core G331.512-0.103

In the interstellar cold gas, the chemistry of formaldehyde (H$_2$CO) can be essential to explain the formation of complex organic molecules. On this matter, the massive and energetic protostellar object G331 is still unexplored and, hence, we carried out a comprehensive study of the isotopologues of H$_2$CO and formyl cation (HCO$^+$), and of protonated formaldehyde (H$_2$COH$^+$) through the APEX observations in the spectral window $\sim$159-356~GHz. We employed observational and theoretical methods to derive the physical properties of the molecular gas combining LTE and non-LTE analyses. Formaldehyde was characterized via 35 lines of H$_2$CO, H$_2^{13}$CO, HDCO and H$_2$C$^{18}$O. The formyl cation was detected via 8 lines of HCO$^+$, H$^{13}$CO$^+$, HC$^{18}$O$^+$ and HC$^{17}$O$^+$. Deuterium was clearly detected via HDCO, whereas DCO$^+$ remained undetected. H$_2$COH$^+$ was detected through 3 clean lines. According to the radiative analysis, formaldehyde appears to be embedded in a bulk gas with a wide range of temperatures ($T\sim$20-90 K), while HCO$^+$ and H$_2$COH$^+$ are primarily associated with a colder gas ($T\lesssim$ 30 K). The reaction H$_2$CO+HCO$^+ \rightarrow$ H$_2$COH$^+$ + CO is crucial for the balance of the three species. We used Nautilus gas-grain code to predict the evolution of their molecular abundances relative to H$_2$ which values at time scales $\sim$10$^3$ yr matched with the observations in G331: [H$_2$CO] = (0.2-2) $\times$10$^{-8}$, [HCO$^+$] = (0.5-4) $\times$10$^{-9}$ and [H$_2$COH$^+$] = (0.2-2) $\times$10$^{-10}$. Based on the molecular evolution of H$_2$CO, HCO$^+$ and H$_2$COH$^+$, we hypothesized about the young lifetime of G331, which is consistent with the active gas-grain chemistry of massive protostellar objects.Comment: 24 pages, 8 figures, 8 tables. Accepted for publication in The Astrophysical Journa