Examinando por Autor "Najarro, F."

Mostrando 1 - 13 de 13

Restringido
2D kinematics of massive stars near the Galactic Centre
(Oxford Academics: Oxford University Press, 2021-01-14) Libralato, M.; Lennon, D. J.; Bellini, A.; Van der Marel, R.; Clark, S. J.; Najarro, F.; Patrick, Lee R.; Anderson, J.; Bedin, L. R.; Crowther, P. A.; Mink, S. E.; Evans, C. J.; Platais, I.; Sabbi, E.; Sohn, S. T.; Agencia Estatal de Investigación (AEI); Agencia Canaria de Investigación, Innovación y Sociedad de la Información (ACIISI); Generalitat Valenciana; Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR); Bedin, L. [0000-0003-4080-6466]; Patrick, L. [0000-0002-9015-0269]; Libralato, M. [0000-0001-9673-7397]
The presence of massive stars (MSs) in the region close to the Galactic Centre (GC) poses several questions about their origin. The harsh environment of the GC favours specific formation scenarios, each of which should imprint characteristic kinematic features on the MSs. We present a 2D kinematic analysis of MSs in a GC region surrounding Sgr A* based on high-precision proper motions obtained with the Hubble Space Telescope. Thanks to a careful data reduction, well-measured bright stars in our proper-motion catalogues have errors better than 0.5 mas yr−1. We discuss the absolute motion of the MSs in the field and their motion relative to Sgr A*, the Arches, and the Quintuplet. For the majority of the MSs, we rule out any distance further than 3–4 kpc from Sgr A* using only kinematic arguments. If their membership to the GC is confirmed, most of the isolated MSs are likely not associated with either the Arches or Quintuplet clusters or Sgr A*. Only a few MSs have proper motions, suggesting that they are likely members of the Arches cluster, in agreement with previous spectroscopic results. Line-of-sight radial velocities and distances are required to shed further light on the origin of most of these massive objects. We also present an analysis of other fast-moving objects in the GC region, finding no clear excess of high-velocity escaping stars. We make our astro-photometric catalogues publicly available.
Acceso Abierto
A New Candidate Luminous Blue Variable
(The Institute of Physics (IOP), 2020-09-23) Figer, D. F.; Najarro, F.; Messineo, M.; Clark, J. S.; Menten, K. M.; National Natural Science Foundation of China (NSFC); Agencia Estatal de Investigación (AEI); Figer, D. F. [0000-0002-4206-733X]; Najarro, F. [0000-0002-9124-0039]; Messineo, M. [0000-0002-7198-1518]; Menten, K. M. [0000-0001-6459-0669]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We identify IRAS 16115-5044, which was previously classified as a protoplanetary nebula (PPN), as a candidate luminous blue variable (LBV). The star has high luminosity (greater than or similar to 10(5.75)L), ensuring supergiant status, has a temperature similar to LBVs, is photometrically and spectroscopically variable, and is surrounded by warm dust. Its near-infrared spectrum shows the presence of several lines of Hi, Hei, Feii, Fe [ii], Mgii, and Naiwith shapes ranging from pure absorption and P Cygni profiles to full emission. These characteristics are often observed together in the relatively rare LBV class of stars, of which only 20 are known in the Galaxy. The key to the new classification is the fact that we compute a new distance and extinction that yield a luminosity significantly in excess of those for post-AGB PPNe, for which the initial masses are M. Assuming single star evolution, we estimate an initial mass of 40 M.
Acceso Abierto
A significant feature in the general relativistic time evolution of the redshift of photons coming from a star orbiting Sgr A
(Oxford Academics: Oxford University Press, 2019-10-22) Saida, H.; Nishiyama, S.; Ohgami, T.; Takamori, Y.; Takahashi, M.; Minowa, Y.; Najarro, F.; Hamano, S.; Omiya, M.; Iwamatsu, A.; Takahashi, M.; Gorin, H.; Kara, T.; Koyama, A.; Ohashi, Y.; Tamura, M.; Nagatomo, S.; Zenko, T.; Nagata, T.; Japan Society for the Promotion of Science (KAKENHI); Nishiyama, S. [https://orcid.org/0000-0002-9440-7172]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The star S0-2, orbiting the Galactic central massive black hole candidate Sgr A*, passed its pericenter in 2018 May. This event is the first chance to detect the general relativistic (GR) effect of a massive black hole, free from non-gravitational physics. The observable GR evidence in the event is the difference between the GR redshift and the Newtonian redshift of photons coming from S0-2. Within the present observational precision, the first post-Newtonian (1PN) GR evidence is detectable. In this paper, we give a theoretical analysis of the time evolution of the 1PN GR evidence, under a presupposition that is different from used in previous papers. Our presupposition is that the GR/Newtonian redshift is always calculated with the parameter values (the mass of Sgr A*, the initial conditions of S0-2, and so on) determined by fitting the GR/Newtonian motion of S0-2 with the observational data. It is then revealed that the difference of the GR redshift and the Newtonian one shows two peaks before and after the pericenter passage. This double-peak appearance is due to our presupposition, and reduces to a single peak if the same parameter values are used in both GR and Newtonian redshifts as considered in previous papers. In addition to this theoretical discussion, we report our observational data obtained with the Subaru telescope by 2018. The quality and the number of Subaru data in 2018 are not sufficient to confirm the detection of the double-peak appearance.
Acceso Abierto
Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds V. Complete comoving frame transfer, and updated modeling of X-ray emission
(EDP Sciences, 2020-10-19) Puls, J.; Najarro, F.; Sundqvist, J. O.; Sen, K.; Agencia Estatal de Investigación (AEI); Research Foundation Flanders (FWO); 0000-0002-0874-1669; 0000-0002-9124-0039; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Obtaining precise stellar and wind properties and abundance patterns of massive stars is crucial to understanding their nature and interactions with their environments, as well as to constrain their evolutionary paths and end-products. Aims. To enable higher versatility and precision of the complete ultraviolet (UV) to optical range, we improve our high-performance, unified, NLTE atmosphere and spectrum synthesis code FASTWIND. Moreover, we aim to obtain an advanced description of X-ray emission from wind-embedded shocks, consistent with alternative modeling approaches. Methods. We include a detailed comoving frame radiative transfer for the essential frequency range, but still apply methods that enable low turnaround times. We compare the results of our updated computations with those from the alternative code CMFGEN, and our previous FASTWIND version, for a representative model grid. Results. In most cases, our new results agree excellently with those from CMFGEN, both regarding the total radiative acceleration, strategic optical lines, and the UV-range. Moderate differences concern He II λλ4200-4541 and N V λλ4603-4619. The agreement regarding N III λλ4634−4640−4642 has improved, though there are still certain discrepancies, mostly related to line overlap effects in the extreme ultraviolet, depending on abundances and micro-turbulence. In the UV range of our coolest models, we find differences in the predicted depression of the pseudo-continuum, which is most pronounced around Lyα. This depression is larger in CMFGEN, and related to different Fe IV atomic data. The comparison between our new and previous FASTWIND version reveals an almost perfect agreement, except again for N V λλ4603-4619. Using an improved, depth-dependent description for the filling factors of hot, X-ray emitting material, we confirm previous analytic scaling relations with our numerical models. Conclusions. We warn against uncritically relying on transitions, which are strongly affected by direct or indirect line-overlap effects. The predicted UV-continuum depression for the coolest grid-models needs to be checked, both observationally, and regarding the underlying atomic data. Wind lines from “super-ionized” ions such as O VI can, in principle, be used to constrain the distribution of wind-embedded shocks. The new FASTWIND version v11 is now ready to be used.
Acceso Abierto
Constraining the population of isolated massive stars within the Central Molecular Zone
(EDP Sciences, 2021-05-10) Clark, J. S.; Patrick, Lee R.; Najarro, F.; Evans, C. J.; Lohr, M.; Generalitat Valenciana; Agencia Estatal de Investigación (AEI); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Many galaxies host pronounced circumnuclear starbursts, fuelled by infalling gas. Such activity is expected to drive the secular evolution of the nucleus and generate super winds which enrich the interstellar and intergalactic medium. Moreover, given the intense radiation fields and extreme gas and cosmic ray densities present within such regions, one might question whether star formation proceeds in a different manner to that occurring in more quiescent regions of the galactic disc, potentially leading to a dependence of the stellar initial mass function on the local environment. Aims. To address the physics of circumnuclear starbursts, we are driven to observe the centre of our own Galaxy, which is the only example where individual stars may be resolved. Previous studies have revealed a rich population of very massive stars, found in three young massive clusters as well as being distributed, in apparent isolation, throughout the inner ∼500 pc of the Galaxy. In this paper we investigate the size and composition of the latter cohort in order to constrain its origin and role in the lifecycle of the Galactic Centre. Methods. To accomplish this, we utilised the Very Large Telescope + K-band Multi-Object Spectrograph to obtain homogeneous, high signal-to-noise ratio observations of known and candidate massive stars suitable for spectral classification and quantitative analysis. Results. We identified 17 new isolated massive stars and reclassified a further 19 known examples, leading to a total of at least 83 within the Galactic Centre. Due to the selection criteria employed, these were strongly biased towards stars with powerful stellar winds and/or extensive circumstellar envelopes; as such, we suspect the resultant census to be incomplete. No further stellar clusters, or their tidally stripped remnants, were identified, although an apparent overdensity of very young and massive stars is found to be coincident with the Sgr B1 star forming region. Conclusions. Despite the limitations of the current dataset, the size of the cohort of outlying massive stars within the Galactic Centre is directly comparable to that of the known clusters and, assuming a comparable mass function, is expected to exceed this number. Combining both cluster and isolated populations yields ≳320 spectroscopically classified stars within the Galactic Centre that are sufficiently massive that they might be anticipated to undergo core collapse within the next ∼20 Myr. Given this is almost certainly a substantial underestimate of the true number, the population of massive stars associated with the Galactic Centre appears unprecedented within the Milky Way, and it appears unavoidable that they play a substantial role in the energetics and evolution of this region.
Restringido
Early formation and recent starburst activity in the nuclear disk of the Milky Way.
(Nature Research Journals, 2020-04-01) Nogueras Lara, F.; Schödel, R.; Gallego Calvente, A. T.; Gallego Cano, E.; Shahzamanian, B.; Dong, H.; Neumayer, N.; Hilker, M.; Najarro, F.; Nishiyama, S.; Feldmeier Krause, A.; Girard, J. H. V.; Cassisi, S.; European Commission (EC); Ministerio de Educación, Cultura y Deporte (MECD); Agencia Estatal de Investigación (AEI); 0000-0001-5870-3735; 0000-0002-2363-5522; 0000-0002-7452-1496; 0000-0002-6922-2598; 0000-0002-6379-7593; 0000-0001-6437-6806; 0000-0002-0160-7221; 0000-0001-8627-0404; 0000-0002-6428-8045; 0000-0002-9440-7172; 0000-0001-5404-797X; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The nuclear disk is a dense stellar structure at the centre of the Milky Way, with a radius of ~150 pc (ref. (1)). It has been a place of intense star formation in the past several tens of millions of years(1-3), but its overall formation history has remained unknown(2). Here, we report that the bulk of its stars formed at least 8 Gyr ago. After a long period of quiescence, a starburst event followed about 1 Gyr ago that formed roughly 5% of its mass within ~100 Myr, in what may arguably have been one of the most energetic events in the history of the Milky Way. Star formation continued subsequently on a lower level, creating a few per cent of the stellar mass in the past ~500 Myr, with an increased rate up to ~30 Myr ago. Our findings contradict the previously accepted paradigm of quasi-continuous star formation at the Galactic Centre(4). The long quiescent phase agrees with the overall quiescent history of the Milky Way(2,5) and suggests that our Galaxy's bar may not have existed until recently, or that gas transport through the bar was extremely inefficient during a long stretch of the Milky Way's life. Consequently, the central black hole may have acquired most of its mass already in the early days of the Milky Way.
Acceso Abierto
GALACTICNUCLEUS: A high angular-resolution JHKs imaging survey of the Galactic centre III. Evidence for wavelength-dependence of the extinction curve in the near-infrared
(EDP Sciences, 2020-09-24) Nogueras Lara, F.; Schödel, R.; Neumayer, N.; Gallego Cano, E.; Shahzamanian, B.; Gallego Calvente, A. T.; Najarro, F.; Agencia Estatal de Investigación (AEI); Deutsche Forschungsgemeinschaft (DFG); European Commission (EC); Nogueras Lara, F. [0000-0002-6379-7593]; Schödel, R. [0000-0001-5404-797X]; Neumayer, N. [0000-0002-6922-2598]; Gallego Cano, E. [0000-0002-7452-1496]; Shahzamanian, B. [0000-0001-6437-6806]; Gallego Calvente, A. T. [0000-0002-6428-8045]; Najarro, F. [0000-0002-9124-0039]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The characterisation of the extinction curve in the near-infrared (NIR) is fundamental to analysing the structure and stellar population of the Galactic centre (GC), whose analysis is hampered by the extreme interstellar extinction (AV ~ 30 mag) that varies on arc-second scales. Recent studies indicate that the behaviour of the extinction curve might be more complex than previously assumed, pointing towards a variation of the extinction curve as a function of wavelength. Aims. We aim to analyse the variations of the extinction index, α, with wavelength, line-of-sight, and absolute extinction, extending previous analyses to a larger area of the innermost regions of the Galaxy. Methods. We analysed the whole GALACTICNUCLEUS survey, a high-angular resolution (~0.2″) JHKs NIR survey specially designed to observe the GC in unprecedented detail. It covers a region of ~6000 pc2, comprising fields in the nuclear stellar disc, the inner bulge, and the transition region between them. We applied two independent methods based on red clump (RC) stars to constrain the extinction curve and analysed its variation superseding previous studies. Results. We used more than 165 000 RC stars and increased the size of the regions analysed significantly to confirm that the extinction curve varies with the wavelength. We estimated a difference Δα = 0.21 ± 0.07 between the obtained extinction indices, αJH = 2.44 ± 0.05 and αHKs = 2.23 ± 0.05. We also concluded that there is no significant variation of the extinction curve with wavelength, with the line-of-sight or the absolute extinction. Finally, we computed the ratios between extinctions, AJ/AH = 1.87 ± 0.03 and AH/AKs = 1.84 ± 0.03, consistent with all the regions of the GALACTICNUCLEUS catalogue. © F. Nogueras-Lara et al. 2020.
Acceso Abierto
GALACTICNUCLEUS: A high-angular-resolution JHKs imaging survey of the Galactic centre II. First data release of the catalogue and the most detailed CMDs of the GC
(EDP Sciences, 2019-10-15) Nogueras Lara, F.; Schödel, R.; Gallego Calvente, A. T.; Dong, H.; Gallego Cano, E.; Shahzamanian, B.; Girard, J. H. V.; Nishiyama, S.; Najarro, F.; Neumayer, N.; European Commission (EC); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Deutsche Forschungsgemeinschaft (DFG); Nogueras Lara, F. [0000-0002-6379-7593]; Schöedel, R. [0000-0001-5404-797X]; Gallego Calvente, A. T. [0000-0002-6428-8045]; Gallego Cano, E. [0000-0002-7452-1496]; Shahzamanian, B. [0000-0001-6437-6806]; Najarro, F. [0000-0002-9124-0039]; Neumayer, N. [0000-0002-6922-2598]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Existing surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high-angular-resolution survey in the near infrared is crucial to improve the state of the art. Aims. Here, we present the GALACTICNUCLEUS catalogue, a near infrared JHKs high-angular-resolution (0.2″) survey of the nuclear bulge of the Milky Way. Methods. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. Results. We obtained accurate JHKs photometry for ∼3.3 × 106 stars in the GC detecting around 20% in J, 65% in H, and 90% in Ks. The survey covers a total area of ∼0.3 deg2, which corresponds to ∼6000 pc2. The GALACTICNUCLEUS survey reaches 5σ detections for J ∼ 22 mag, H ∼ 21 mag, and Ks ∼ 21 mag. The uncertainties are below 0.05 mag at J ∼ 21 mag, H ∼ 19 mag, and Ks ∼ 18 mag. The zero point systematic uncertainty is ≲0.04 mag in all three bands. We present colour–magnitude diagrams for the different regions covered by the survey.
Acceso Abierto
New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars II. A grid of O-type stars in the Galaxy and the Magellanic Clouds
(EDP Sciences, 2021-04-08) Björklund, R.; Sundqvist, J. O.; Puls, J.; Najarro, F.; Agencia Estatal de Investigación (AEI); Sundqvist, J. O. [0000-0003-1729-1273]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Reliable predictions of mass-loss rates are important for massive-star evolution computations. Aims. We aim to provide predictions for mass-loss rates and wind-momentum rates of O-type stars, while carefully studying the behaviour of these winds as functions of stellar parameters, such as luminosity and metallicity. Methods. We used newly developed steady-state models of radiation-driven winds to compute the global properties of a grid of O-stars. The self-consistent models were calculated by means of an iterative solution to the equation of motion using full non-local thermodynamic equilibrium radiative transfer in the co-moving frame to compute the radiative acceleration. In order to study winds in different galactic environments, the grid covers main-sequence stars, giants, and supergiants in the Galaxy and both Magellanic Clouds. Results. We find a strong dependence of mass-loss on both luminosity and metallicity. Mean values across the grid are Ṁ~L*2.2 and Ṁ~L*0.95; however, we also find a somewhat stronger dependence on metallicity for lower luminosities. Similarly, the mass loss-luminosity relation is somewhat steeper for the Small Magellanic Cloud (SMC) than for the Galaxy. In addition, the computed rates are systematically lower (by a factor 2 and more) than those commonly used in stellar-evolution calculations. Overall, our results are in good agreement with observations in the Galaxy that properly account for wind-clumping, with empirical Ṁ versus Z* scaling relations and with observations of O-dwarfs in the SMC. Conclusions. Our results provide simple fit relations for mass-loss rates and wind momenta of massive O-stars stars as functions of luminosity and metallicity, which are valid in the range Teff = 28 000–45 000 K. Due to the systematically lower values for Ṁ, our new models suggest that new rates might be needed in evolution simulations of massive stars.
Acceso Abierto
Radio observations of massive stars in the Galactic centre: The Arches Cluster⋆
(EDP Sciences, 2021-03-17) Gallego Calvente, A. T.; Schödel, R.; Alberdi, A.; Herrero Illana, R.; Najarro, F.; Yusef Zadeh, F.; Dong, H.; Sánchez Bermudez, J.; Shahzamanian, B.; Nogueras Lara, F.; Gallego Cano, E.; Deutsche Forschungsgemeinschaft (DFG); European Commssion (EC); Agencia Estatal de Investigación (AEI); 0000-0002-6428-8045; 0000-0001-5404-797X; 0000-0002-9371-1033; 0000-0001-6437-6806; 0000-0002-6379-7593; 0000-0002-7452-1496; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present high-angular-resolution radio observations of the Arches cluster in the Galactic centre, one of the most massive young clusters in the Milky Way. The data were acquired in two epochs and at 6 and 10 GHz with the Karl G. Jansky Very Large Array. The rms noise reached is three to four times better than during previous observations and we have almost doubled the number of known radio stars in the cluster. Nine of them have spectral indices consistent with thermal emission from ionised stellar winds, one is a confirmed colliding wind binary, and two sources are ambiguous cases. Regarding variability, the radio emission appears to be stable on timescales of a few to ten years. Finally, we show that the number of radio stars can be used as a tool for constraining the age and/or mass of a cluster and also its mass function.
Restringido
The 4K focal plane unit for SPICA's SAFARI far infrared instrument
(SPIE Digital Library, 2020-12-13) Torres Redondo, J.; Eggens, M.; García López, Rafael; Pérez Grande, I.; Pérez Álvarez, J.; Chimeno, M.; Arrazola Pérez, D.; Fernández, María Manuela; Belenguer Dávila, T.; González Fernández, L.; Evers, J.; Dieleman, P.; Jellema, W.; Roelfsema, P.; Martín Pintado, J.; Najarro, F.
SPICA provided the next step in mid- and far-infrared astronomical research and was a candidate of ESA's fifth medium class Cosmic Vision mission. SAFARI is one of the spectroscopic instruments on board SPICA. The Focal Plane Unit (FPU) design and analysis represent a challenge both from the mechanical and thermal point of view, as the instrument is working at cryogenic temperatures between 4.8K and 0.05K. Being a large instrument, with a current best estimate of 148,7kg of mass, its design will have to be optimized to fit within the mission´s mass and volume budget. The FPU will also have to be designed for its modularity and accessibility due to the large number of subsystems that SAFARI had to accommodate, highlighting Fourier Transform Spectrometer Mechanism (FTSM) and the three grating-based point source spectrometer modules (GM) which operates at 1.7K in the FPU, the latter representing 60% of the total mass of the instrument
Acceso Abierto
The VLT-FLAMES Tarantula Survey
(Astronomical Science, 2020-09-01) Evans, C. J.; Lennon, D.; Langer, N.; Almeida, L.; Bartlett, E.; Bastian, N.; Bestenlehner, J. M.; Britavskiy, N.; Castro, N.; Clark, S.; Crowther, P. A.; De Koter, A.; De Mink, S.; Dufton, P. L.; Fossati, L.; García, M.; Gieles, M.; Gräfener, G.; Grin, N.; Hénault Brunet, V.; Herrero, A.; Howarth, I.; Izzard, R.; Kalari, V.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Patrick, Lee R.; Puls, J.; Ramírez Agudelo, O.; Renzo, M.; Sabín Sanjulián, C.; Sana, H.; Schneider, F.; Schootemeijer, A.; Simón Díaz, S.; Smartt, S.; Taylor, W.; Tramper, F.; Van Loon, J.; Villaseñor, J.; Vink, J. S.; Walborn, N.
The VLT-FLAMES Tarantula Survey (VFTS) was an ESO Large Programme that has provided a rich, legacy dataset for studies of both resolved and integrated populations of massive stars. Initiated in 2008 (ESO Period 82), we used the Fibre Large Array Multi Element Spectrograph (FLAMES) to observe more than 800 massive stars in the dramatic 30 Doradus star-forming region in the Large Magellanic Cloud. At the start of the survey the importance of multiplicity among high-mass stars was becoming evident, so a key feature was multi-epoch spectroscopy to detect radial-velocity shifts arising from binary motion. Here we summarise some of the highlights from the survey and look ahead to the future of the field.
Acceso Abierto
Variability of the near-infrared extinction curve towards the Galactic centre
(EDP Sciences, 2019-09-23) Nogueras Lara, F.; Schödel, R.; Najarro, F.; Gallego Calvente, A. T.; Gallego Cano, E.; Shahzamanian, B.; Neumayer, N.; European Commission (EC); European Southern Observatory (ESO); Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); Nogueras Lara, F. [0000-0002-6379-7593]; Schöedel, R. [0000-0001-5404-797X]; Gallego Calvente, A. T. [0000-0002-6428-8045]; Shahzamanian, B. [0000-0001-6437-6806]; Neumayer, N. [0000-0002-6922-2598]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. Due to the extreme extinction towards the Galactic centre (AV ∼ 30 mag), its stellar population is mainly studied in the near-infrared (NIR) regime. Therefore, a proper analysis of the NIR extinction curve is necessary to fully characterise the stellar structure and population of the inner part of the galaxy. Aims. We studied the dependence of the extinction index (αλ) in the NIR on the line of sight, wavelength, and extinction. Methods. We used the GALACTICNUCLEUS imaging survey, a high angular resolution catalogue (0.2″) for the inner part of the Galaxy in JHKs, and studied the spatial variation in the extinction index. We also applied two independent methods based on red clump stars to compute the extinction index between different bands and its variation with wavelength. Results. We did not detect any significant line-of-sight or extinction variation in α within the studied region in the nuclear stellar disc. The extinction index between JH and HKs differs by 0.19 ± 0.05. We obtained mean values for the extinction indices αJH = 2.43 ± 0.03 and αHKs = 2.23 ± 0.03. The dependence of the extinction index on the wavelength could explain the differences obtained for αλ in the literature since it was assumed constant for the NIR regime.