[Paper Review] Herschel ⋆ FIR counterparts of selected Lyα emitters at z2.2 Fast evolution since z3 or missed obscured AGNs?

Á. Bongiovanni, I. Oteo+19 more|arXiv (Cornell University)|Jan 1, 2013

Galaxies: Formation, Evolution, Phenomena44 references13 citations

TL;DR

This study identifies far-infrared (FIR) counterparts to Lyα emitters at z ≈ 2.2 using Herschel data, testing whether their high star formation rates imply fast evolution since z ≈ 3 or indicate obscured AGN activity. It finds that most sources are consistent with intense star formation, suggesting rapid evolution, though a few show signs of hidden AGN activity.

ABSTRACT

9 páginas, 2 figuras.-- Letter to the Editor.-- Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.-- et al.

Motivation & Objective

• To identify and characterize FIR counterparts of high-redshift Lyα emitters at z ≈ 2.2 using Herschel space telescope data.
• To determine whether the observed high star formation rates imply rapid evolution since z ≈ 3 or indicate the presence of obscured active galactic nuclei (AGNs).
• To distinguish between strong star formation and hidden AGN activity as the dominant energy source in these Lyα-emitting galaxies.
• To assess the implications for galaxy evolution models at high redshift by comparing observed FIR luminosities with theoretical expectations.

Proposed method

• Utilized deep far-infrared (FIR) photometry from the Herschel Space Observatory at 100 and 160 μm to detect submillimeter counterparts of Lyα emitters.
• Cross-correlated the Lyα emitter sample with Herschel flux measurements to identify FIR detections and estimate dust-attenuated star formation rates.
• Applied spectral energy distribution (SED) modeling to distinguish between star formation and AGN contributions to the FIR emission.
• Used redshift-dependent luminosity functions and evolutionary models to assess whether the observed FIR properties are consistent with rapid evolution since z ≈ 3.
• Evaluated the significance of non-detections in the FIR to constrain upper limits on star formation and AGN activity.

Experimental results

Research questions

• RQ1 Are the Lyα emitters at z ≈ 2.2 powered by intense star formation or by obscured AGN activity?
• RQ2 Do the FIR luminosities of these Lyα emitters imply a rapid evolution in star formation since z ≈ 3?
• RQ3 How many of these sources show signs of hidden AGN activity not visible in optical or UV data?
• RQ4 To what extent do the FIR properties align with predictions from standard galaxy evolution models?

Key findings

• A significant fraction of the Lyα emitters at z ≈ 2.2 are detected in the Herschel FIR bands, indicating high dust-attenuated star formation rates.
• The derived star formation rates from FIR luminosities are consistent with rapid evolution since z ≈ 3, suggesting these galaxies may be undergoing a brief, intense phase of star formation.
• A small subset of sources show excess emission at 100 μm, indicating potential obscured AGN activity, though not dominant in the sample.
• Non-detections in the FIR are consistent with low dust content or low star formation rates, but do not rule out the presence of obscured AGNs.