EMIR confirmation of the high- z Ly α blob SHARDS20018464
- 1Centro de Estudios de Física del Cosmos de Aragón
- 2Instituto de Astrofísica de Canarias, IAC
- 3Departamento de Astrofísica, Universidad de La Laguna
Abstract
Aims. We performed a spectroscopic follow-up of the Ly α blob SHARDS20018464 using the infrared spectrograph Espectrógrafo Multiobjeto Infra-Rojo (EMIR) at the 10.4 m Gran Telescopio Canarias (GTC) telescope, equipped with its newly upgraded H2RG focal plane array detector.
Methods. We observed the blob in the Ks band, which corresponds, at the photometric redshift of z = 3.49 presented in the literature, to the visible part of the spectrum in the rest-frame.
Results. 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 , which we obtained with a 4-hour exposure. The mean redshift derived by analysing the two lines individually is z = 3.59 ± 0.01 and thus 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 we found to be R = 2.92, very close to the theoretical prediction of 2.98. This is an analytical confirmation that the observed emissions correspond to the [OIII] doublet.
Conclusions. Within uncertainties, the redshift of the blob confirms the photometric redshift reported in the literature as well as the physical properties inferred for it. The blob’s remarkably small size (5−8 kpc versus ∼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 Ly α emitters. Moreover, the data support the scenario of photoionisation due to a cluster of young and massive stars.
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BibTeX
@article{zarattini2026emir,
title = {{EMIR confirmation of the high- z Ly α blob SHARDS20018464}},
author = {S. Zarattini and F. Garzón and C. Muñoz Tuñón},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202662313},
url = {https://www.aanda.org/10.1051/0004-6361/202662313},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - EMIR confirmation of the high- z Ly α blob SHARDS20018464
AU - S. Zarattini
AU - F. Garzón
AU - C. Muñoz Tuñón
PY - 2026
DA - 2026/10/26
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202662313
UR - https://www.aanda.org/10.1051/0004-6361/202662313
AB - Aims. We performed a spectroscopic follow-up of the Ly α blob SHARDS20018464 using the infrared spectrograph Espectrógrafo Multiobjeto Infra-Rojo (EMIR) at the 10.4 m Gran Telescopio Canarias (GTC) telescope, equipped with its newly upgraded H2RG focal plane array detector. Methods. We observed the blob in the Ks band, which corresponds, at the photometric redshift of z = 3.49 presented in the literature, to the visible part of the spectrum in the rest-frame. Results. 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 , which we obtained with a 4-hour exposure. The mean redshift derived by analysing the two lines individually is z = 3.59 ± 0.01 and thus 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 we found to be R = 2.92, very close to the theoretical prediction of 2.98. This is an analytical confirmation that the observed emissions correspond to the [OIII] doublet. Conclusions. Within uncertainties, the redshift of the blob confirms the photometric redshift reported in the literature as well as the physical properties inferred for it. The blob’s remarkably small size (5−8 kpc versus ∼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 Ly α emitters. Moreover, the data support the scenario of photoionisation due to a cluster of young and massive stars.
SN - 0004-6361
SN - 1432-0746
ER -