The Arecibo Galaxy Environment Survey VII : A Dense Filament With Extremely Long HI Streams

TL;DR

This paper reports on the detailed HI observations of the NGC 7448 galaxy group, revealing a dense filament with extremely long HI streams, high galaxy density, and extended HI features, along with new tools for data analysis.

Contribution

It provides new high-resolution HI data of a dense galaxy environment and introduces a novel FITS viewer tool for efficient source cataloguing.

Findings

High galaxy density of 15 per square degree.

Detection of HI streams up to 800 kpc long.

Identification of multiple overdensities in the surveyed volume.

Abstract

We present completed observations of the NGC 7448 galaxy group and background volume as part of the blind neutral hydrogen Arecibo Galaxy Environment Survey (AGES). Our observations cover a region spanning 5x4 degrees, over a redshift range of approximately -2,000 < cz < 20,000 km/s. A total of 334 objects are detected, mostly in three overdensities at cz $\sim$7,500, cz $\sim$9,600 and cz $\sim$ 11,400 km/s. The galaxy density is extremely high (15 per square degree) and many ($\sim$24%) show signs of extended HI emission, including some features as much as 800 kpc in projected length. We describe the overall characteristics of this environment : kinematics, typical galaxy colours and mass to light ratios, and substructure. To aid in the cataloguing of this data set, we present a new FITS viewer (FRELLED : Fits Realtime Explorer of Low Latency in Every Dimension). This incorporates interactive source cataloguing tools which increase our source extraction speed by approximately a factor of 50.