Examinando por Autor "Nogueras Lara, F."

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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
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.
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.