EMIR confirmation of the high-z Lyα blob SHARDS20018464
Abstract
A spectroscopic follow-up of the Lyα blob SHARDS20018464 was performed using the infrared spectrograph EMIR (Espectrógrafo Multiobjeto Infra-Rojo) at the 10.4 m GTC telescope, equipped with its newly upgraded H2RG focal plane array detector. We observed the blob in the Ks band, which corresponds, at the photometric redshift of z=3.49 presented in the literature, to the rest-frame visible part of the spectrum. Thanks to the sensitivity of EMIR, we were able to identify the [OIII] emission doublet at the position of the blob and the companion galaxy. The flux of the detected lines is of the order of 10−17 erg s−1 cm−2, obtained with 4-hour exposure. The mean redshift derived by analysing the two lines individually is z=3.59±0.01, slightly higher than the photometric one, although in agreement within the uncertainties. We also estimated the flux of the two lines and their ratio, which was found to be R = 2.92, very close to the theoretical prediction of 2.98. This is a strong analytical confirmation that the observed emissions correspond to the [OIII] doublet. Within uncertainties, the redshift of the blob confirms the photometric one reported in the literature, as well as the physical properties inferred for it. Its remarkably small size (5-8 kpc vs. ∼ 100 kpc for typical samples) and its position aside the companion galaxy also confirm the previously-proposed idea that this object could be the first of a new class of compact Lyα emitters. Moreover, the data support the scenario of photo-ionisation due to a cluster of young and massive stars.
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BibTeX
@misc{zarattini2026emir,
title = {{EMIR confirmation of the high-z Lyα blob SHARDS20018464}},
author = {S. Zarattini and F. Garzón and C. Muñoz-Tuñón},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.07068},
eprint = {2610.07068},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.07068},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - EMIR confirmation of the high-z Lyα blob SHARDS20018464
AU - S. Zarattini
AU - F. Garzón
AU - C. Muñoz-Tuñón
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2610.07068
UR - https://arxiv.org/abs/2610.07068
AB - A spectroscopic follow-up of the Lyα blob SHARDS20018464 was performed using the infrared spectrograph EMIR (Espectrógrafo Multiobjeto Infra-Rojo) at the 10.4 m GTC telescope, equipped with its newly upgraded H2RG focal plane array detector. We observed the blob in the Ks band, which corresponds, at the photometric redshift of z=3.49 presented in the literature, to the rest-frame visible part of the spectrum. Thanks to the sensitivity of EMIR, we were able to identify the [OIII] emission doublet at the position of the blob and the companion galaxy. The flux of the detected lines is of the order of 10^−17 erg s^−1 cm^−2, obtained with 4-hour exposure. The mean redshift derived by analysing the two lines individually is z=3.59±0.01, slightly higher than the photometric one, although in agreement within the uncertainties. We also estimated the flux of the two lines and their ratio, which was found to be R = 2.92, very close to the theoretical prediction of 2.98. This is a strong analytical confirmation that the observed emissions correspond to the [OIII] doublet. Within uncertainties, the redshift of the blob confirms the photometric one reported in the literature, as well as the physical properties inferred for it. Its remarkably small size (5-8 kpc vs. ∼ 100 kpc for typical samples) and its position aside the companion galaxy also confirm the previously-proposed idea that this object could be the first of a new class of compact Lyα emitters. Moreover, the data support the scenario of photo-ionisation due to a cluster of young and massive stars.
ER -