# Systematic Survey for [OII], [OIII], and H$\alpha$ Blobs at $z=0.1-1.5$: The Implication for Evolution of Galactic-Scale Outflow

## TL;DR

This study systematically identifies extended emission-line galaxies, called blobs, at redshifts 0.1-1.5, revealing their properties, AGN activity, and evolution, and showing that their number density declines faster than cosmic star formation rates.

## Contribution

It introduces a new selection method for extended emission-line galaxies and provides the first large, homogeneous sample of blobs across a broad redshift range.

## Key findings

- 77 blobs identified at z=0.40-1.46
- AGN activity found in 8 blobs, increasing with size
- Number densities decline faster than cosmic star formation rates

## Abstract

We conduct a systematic search for galaxies at $z=0.1-1.5$ with [OII]$\lambda3727$, [OIII]$\lambda5007$, or H$\alpha\lambda6563$ emission lines extended over at least 30 kpc by using deep narrowband and broadband imaging in Subaru-XMM Deep Survey (SXDS) field. These extended emission-line galaxies are dubbed [OII], [OIII], or H$\alpha$ blobs. Based on a new selection method that securely selects extended emission-line galaxies, we find 77 blobs at $z=0.40-1.46$ with the isophotal area of emission lines down to $1.2\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ kpc$^{-2}$. Four of them are spectroscopically confirmed to be [OIII] blobs at $z=0.83$. We identify AGN activities in 8 blobs with X-ray and radio data and find that the fraction of AGN contribution increases with increasing isophotal area of the extended emission. With the Kolmogorov-Smirnov (KS) and Anderson-Darling tests, we confirm that the stellar-mass distributions of H$\alpha$ and [OII] blobs are not drawn from those of the emitters at the $>90$% confidence level in that H$\alpha$ and [OII] blobs are located at the massive end of the distributions, but cannot reject null hypothesis of being the same distributions in terms of the specific star formation rates. It is suggested that galactic-scale outflows tend to be more prominent in more massive star-forming galaxies. Exploiting our sample homogeneously selected over the large area, we derive the number densities of blobs at each epoch. The number densities of blobs decrease drastically with redshifts at the rate that is larger than that of the decrease of cosmic star formation densities.