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Register a new userHI shells in the Leiden/Argentina/Bonn HI survey
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We analyse the all-sky Leiden/Argentina/Bonn HI survey, where we identify shells belonging to the Milky Way. We used an identification method based on the search of continuous regions of a low brightness temperature that are compatible with given properties of HI shells. We found 333 shells in the whole Galaxy. The size distribution of shells in the outer Galaxy is fitted by a power law with the coefficient of 2.6 corresponding to the index 1.8 in the distribution of energy sources. Their surface density decreases exponentially with a scale length of 2.8 kpc. The surface density of shells with radii >= 100 pc in the solar neighbourhood is around 4 per kpc^2 and the 2D porosity is approximately 0.7.
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The Effelsberg-Bonn HI Survey (EBHIS) covers the whole sky north of Dec(2000) = -5 deg. on a fully sampled angular grid. Using state-of-the-art FPGA-spectrometers we perform a Milky Way and an extragalactic HI survey in parallel. Moreover, the high dynamic range and short dump time of the HI spectra allow to overcome the vast majority of all radio-frequency-interference (RFI) events. The Milky Way data will be corrected for the stray-radiation bias which warrants a main-beam efficiency of 99%. Towards the whole survey area we exceed the sensitivity limit of HIPASS, while towards the Sloan-Digital-Sky-Survey (SDSS) area EBHIS offers an order of magnitude higher mass sensitivity. The Milky Way data will be a cornerstone for multi-frequency astrophysics, while the extragalactic part will disclose detailed information on the structure formation of the local universe.
The Effelsberg-Bonn HI survey (EBHIS) comprises an all-sky survey north of Dec = -5 degrees of the Milky Way and the local volume out to a red-shift of z ~ 0.07. Using state of the art Field Programmable Gate Array (FPGA) spectrometers it is feasible to cover the 100 MHz bandwidth with 16.384 spectral channels. High speed storage of HI spectra allows us to minimize the degradation by Radio Frequency Interference (RFI) signals. Regular EBHIS survey observations started during the winter season 2008/2009 after extensive system evaluation and verification tests. Until today, we surveyed about 8000 square degrees, focusing during the first all-sky coverage of the Sloan-Digital Sky Survey (SDSS) area and the northern extension of the Magellanic stream. The first whole sky coverage will be finished in 2011. Already this first coverage will reach the same sensitivity level as the Parkes Milky Way (GASS) and extragalactic surveys (HIPASS). EBHIS data will be calibrated, stray-radiation corrected and freely accessible for the scientific community via a web-interface. In this paper we demonstrate the scientific data quality and explore the expected harvest of this new all-sky survey.
The new L-band 7-feed-array at the 100-m telescope in Effelsberg will be used to perform an unbiased fully sampled HI survey of the entire northern hemisphere observing the galactic and extragalactic sky using simultaneously two different backends. The survey will be extremely valuable for a broad range of research topics: study of the low-mass end of the HI mass function (HIMF) in the local volume, environmental and evolutionary effects (as seen in the HIMF), the search for galaxies near low-redshift Lyman-alpha absorbers, and analysis of multiphase and extraplanar gas, HI shells, and ultra-compact high-velocity-clouds.
Since autumn 2008 a new L-band 7-Feed-Array receiver is used for an HI 21-cm line survey performed with the 100-m Effelsberg telescope. The survey will cover the whole northern hemisphere comprising both, the galactic and extragalactic sky in parallel. Using state-of-the-art FPGA based digital Fast Fourier Transform spectrometers, superior in dynamic range and temporal resolution, allows to apply sophisticated radio frequency interferences (RFI) mitigation schemes to the survey data. The EBHIS data reduction software includes the RFI mitigation, gain-curve correction, intensity calibration, stray-radiation correction, gridding, and source detection. We discuss the severe degradation of radio astronomical HI data by RFI signals and the gain in scientific yield when applying modern RFI mitigation schemes. For this aim simulations of the galaxy distribution within the local volume (z<0.07) with and without RFI degradation were performed. These simulations, allow us to investigate potential biases and selection effects introduced by the data reduction software and the applied source parametrization methods.
We present the HI-MaNGA programme of HI follow-up for the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. MaNGA, which is part of the Fourth phase of the Sloan Digital Sky Surveys (SDSS-IV), is in the process of obtaining integral field unit (IFU) spectroscopy for a sample of ~10,000 nearby galaxies. We give an overview of the HI 21cm radio follow-up observing plans and progress and present data for the first 331 galaxies observed in the 2016 observing season at the Robert C. Bryd Green Bank Telescope (GBT). We also provide a cross match of the current MaNGA (DR15) sample with publicly available HI data from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey. The addition of HI data to the MaNGA data set will strengthen the surveys ability to address several of its key science goals that relate to the gas content of galaxies, while also increasing the legacy of this survey for all extragalactic science.
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