Examinando por Autor "Calvi, R."

Mostrando 1 - 4 de 4

Restringido
An ionized superbubble powered by a protocluster at z = 6.5
(Oxford Academics: Oxford University Press, 2020-03-18) Rodríguez Espinosa, J. M.; Mas Hesse, J. M.; Salvador Solé, E.; Calvi, R.; Manrique, Alberto; Chanchaiworawit, K.; Guzman, R.; Gallego, J.; Herrero, A.; Marín Franch, A.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Rodríguez Espinosa, J. M. [0000-0002-0674-1470]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We show herein that a proto-cluster of Ly α emitting galaxies, spectroscopically confirmed at redshift 6.5, produces a remarkable number of ionizing continuum photons. We start from the Ly α fluxes measured in the spectra of the sources detected spectroscopically. From these fluxes, we derive the ionizing emissivity of continuum photons of the protocluster, which we compare with the ionizing emissivity required to reionize the protocluster volume. We find that the sources in the protocluster are capable of ionizing a large bubble, indeed larger than the volume occupied by the protocluster. For various calculations, we have used the model AMIGA, in particular to derive the emissivity of the Lyman continuum photons required to maintain the observed volume ionized. Besides, we have assumed the ionizing photons escape fraction given by AMIGA at this redshift.
Restringido
Is the Bremer Deep Field reionized, at z ∼ 7?
(Oxford Academics: Oxford University Press, 2021-03-01) Rodríguez Espinosa, J. M.; Mas Hesse, J. M.; Calvi, R.; 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
We show herein that the population of star-forming galaxies in the Bremer Deep Field (BDF) has enough ionizing power to form two large ionized bubbles that could be in the process of merging into a large one with a volume of 14 000 cMpc3. The sources identified in the BDF have been completed with a set of expected low-luminosity sources at z ∼ 7. We have estimated the number of ionizing photons per second produced by the different star-forming galaxies in the BDF. This number has been compared with the number that would be required to ionize the bubbles around the two overdense regions. We have used, as reference, ionizing emissivities derived from the AMIGA (Analytic Model of Intergalactic-medium and Galaxies) cosmological evolutionary model. We find that even using the most conservative estimates, with a Lyman continuum escape fraction of 10 per cent⁠, the two regions we have defined within the BDF would be reionized. Assuming more realistic estimates of the ionizing photon production efficiency, both bubbles would be in the process of merging into a large reionized bubble, such as those that through percolation completed the reionization of the Universe by z = 6. The rather small values of the escape fraction required to reionize the BDF are compatible with the low fraction of faint Ly α emitters identified in the BDF. Finally, we confirm that the low-luminosity sources represent indeed the main contributors to the BDF ionizing photon production.
Acceso Abierto
MOS spectroscopy of protocluster candidate galaxies at z = 6.5
(Oxford Academics: Oxford University Press, 2019-08-16) Calvi, R.; Rodríguez Espinosa, J. M.; Mas hesse, J. M.; Chanchaiworawit, K.; Guzman, R.; Salvador Solé, E.; Gallego, J.; Herrero, A.; Manrique, Alberto; Marín Franch, A.; National Astronomical Research Institute of Thailand (NARIT); European Commission (EC); Ministry of Education, Culture, Sports, Science and Technology (MEXT); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Manríque, A. [0000-0001-5339-2659]; Gallego, J. [0000-0003-1439-7697]; Calvi, R. [0000-0002-1462-9462]; 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 ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Unidad de Excelencia Científica María de Maeztu Instituto de Ciencias del Cosmos (ICCUB), MDM-2014-0369
The epoch corresponding to a redshift of z ∼ 6.5 is close to full re-ionization of the Universe, and early enough to provide an intriguing environment to observe the early stage of large-scale structure formation. It is also an epoch that can be used to verify the abundance of a large population of low luminosity star-forming galaxies that are deemed responsible for cosmic re-ionization. Here, we present the results of follow-up multi-object spectroscopy using OSIRIS at Gran Telescopio Canarias of 16 Ly α emitter (LAE) candidates discovered in the Subaru/XMM Newton Deep Survey. We have securely confirmed 10 LAEs with sufficient signal-to-noise ratio of the Ly α emission line. The inferred star formation rates of the confirmed LAEs are on the low side, within the range 0.9–4.7 M⊙ yr−1. However, they show relatively high Ly α rest frame equivalent widths. Finally we have shown that the mechanical energy released by the star formation episodes in these galaxies is enough to create holes in the neutral hydrogen medium such that Lyman continuum photons can escape to the intergalactic medium, thus contributing to the re-ionization of the Universe.
Restringido
Probing the existence of a rich galaxy overdensity at z = 5.2
(Oxford Academics: Oxford University Press, 2021-04-05) Calvi, R.; Dannerbauer, H.; Arrabal Haro, P.; Rodríguez Espinosa, J. M.; Muñoz Tuñón, C.; Pérez González, P. G.; Geier, S.; Ministerio de Economía y Competitividad (MINECO); Agencia Estatal de Investigación (AEI); 0000-0003-4528-5639
We report the results of a pilot spectroscopic program of a region at z = 5.2 in the GOODS-N field containing an overdensity of galaxies around the well-known submillimetre galaxy (SMG) HDF850.1. We have selected candidate cluster members from the optical 25 medium-band photometric catalogue of the project SHARDS (Survey for High-z Absorption Red and Dead Sources). 17 rest-frame ultraviolet (UV)-selected galaxies (LAEs and LBGs) with 5.15 < zphot < 5.27, candidates to be physically associated with the overdensity, have been observed with the instrument OSIRIS at the GranTeCan telescope. 13 out of these 17 (76 per cent) sources have secure spectroscopic confirmations via the Ly α line at the redshift of the galaxy protocluster PCl−HDF850.1, demonstrating the high reliability of our photometric redshift method. 10 out of 13 sources are newly confirmed members. Thus, we increase the number of confirmed members in this overdensity from 13 to 23 objects. In order to fully characterize this structure we combined our data set with the sample from the literature. Beside the SMG HDF850.1, none of the 23 spectroscopically confirmed members are bright in the far-infrared/sub-mm wavelength regime (SFRIR < few hundred M⊙ yr−1). The clustering analysis of the whole sample of 23 confirmed members reveals four distinct components in physical space in different evolutionary states, within Δz < 0.04 from the central region hosting SMG HDF850.1. The halo mass of the whole structure at z = 5.2, estimated by a variety of methods, range between 2 and 8×1012M⊙⁠. The comparison with literature suggests a large-scale assembly comparable to the formation of a central Virgo-like cluster at z = 0 with several satellite components which will possibly be incorporated in a single halo if the protocluster is the progenitor of a more massive Coma-like cluster (⁠>1015M⊙⁠).