The Lockman–SpReSO project

Galactic flows in a sample of far-infrared galaxies

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
e-mail: mauro.gonzalez@iac.es; mauromarago@gmail.com
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
³ Fundación Galileo Galilei-INAF, Rambla José Ana Fernández Pérez, 7, 38712 Breña Baja, Tenerife, Spain
⁴ Asociación Astrofísica para la Promoción de la Investigación, Instrumentación y su Desarrollo, ASPID, 38205 La Laguna, Tenerife, Spain
⁵ Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), 39005 Santander, Spain
⁶ Centro de Astrobiología (CSIC/INTA), 28692 ESAC Campus, Villanueva de la Cañada, Madrid, Spain
⁷ Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, 04510 Ciudad de México, Mexico
⁸ Institut de Radioastronomie Millimétrique (IRAM), Av. Divina Pastora 7, Núcleo Central, 18012 Granada, Spain
⁹ Departamento de Física de la Tierra y Astrofísica, Instituto de Física de Partículas y del Cosmos, IPARCOS, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain
¹⁰ ISDEFE for European Space Astronomy Centre (ESAC)/ESA, PO Box 78 28690 Villanueva de la Cañada, Madrid, Spain
¹¹ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
¹² Space Science and Geospatial Institute (SSGI), Entoto Observatory and Research Center (EORC), Astronomy and Astrophysics Research Division, PO Box 33679 Addis Abbaba, Ethiopia
¹³ Instituto de Astrofísica de Andalucía (CSIC), 18080 Granada, Spain
¹⁴ Physics Department, Mbarara University of Science and Technology (MUST), Mbarara, Uganda

Received: 29 August 2023
Accepted: 8 January 2024

Abstract

Context. The Lockman–SpReSO project is an optical spectroscopic survey of 956 far-infrared (FIR) objects within the Lockman Hole field limited by magnitude R_C(AB) < 24.5. Fe II and Mg II absorption lines have been detected in 21 out of 456 objects with a determined spectroscopic redshift in the catalogue. The redshifts of these objects are in the range 0.5 ≲ z ≲ 1.44.

Aims. The aim of this study is to investigate material ejection from star-forming regions and material infall into galaxies by analysing the Fe II and Mg II absorption lines. Additionally, we explore whether the correlations found in previous studies between these galactic wind velocities, line equivalent widths (EWs), and galaxy properties such as stellar mass (M_*), star formation rate (SFR), and specific star formation rate (sSFR) are valid for a sample with FIR-selected objects. The objects analysed span an M_* range of 9.89 < log(M_*/M_⊙) < 11.50 and an SFR range of 1.01 < log(SFR) < 2.70.

Methods. We performed measurements of the Mg IIλλ2796, 2803, Mg Iλ2852, Fe IIλλ2374, 82, Fe IIλλ2586, 2600, and Fe IIλ2344 spectral lines present in the spectra of the selected sample to determine the EW and velocity of the flows observed in the star-forming galaxies. Subsequently, we conducted 10⁷ bootstrap simulations using the Spearman’s rank correlation coefficient (ρ_s) to explore correlations with galaxy properties. Furthermore, we calculated the covering factor, gas density, and optical depth for the measured Fe II doublets.

Results. Our analysis reveals strong correlations between the EW of Mg II lines and both M_* (ρ_s = 0.43, 4.5σ) and SFR (ρ_s = 0.42, 4.4σ). For the Fe II lines, we observed strong correlations between the EW and SFR (ρ_s ∼ 0.65, > 3.9σ), with a weaker correlation for M_* (ρ_s ∼ 0.35, > 1.9σ). No notable correlations were found between velocity measurements of the Mg II line and M_*, SFR, or sSFR of the objects (ρ_s ∼ 0.1). However, a strong negative correlation was found between the velocity of the Fe II lines and the SFR of the galaxies (ρ_s ∼ −0.45, ∼3σ). Our results align with those of previous studies, although only FIR-selected objects are investigated here. Finally, we detect a candidate ‘loitering outflow’, a recently discovered subtype of the iron low-ionisation broad absorption line (FeLoBAL) quasars, at a redshift of z = 1.4399, exhibiting emission in C III] and low line velocities (|v|≲200 km s⁻¹).