Kalberla, P.M.W.

Kerp, J.

Winkle, B.

English

The Effelsberg-Bonn HI Survey (EBHIS) covers the whole sky north of Dec(2000)= −5◦ on a fully sampled angular grid. Using state-of-the-art FPGA-spectrometers we perform a MilkyWay 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. TheMilkyWay data will be a cornerstone for multi-frequency astrophyics, while the extragalactic part will disclose detailed information on the structure formation of the local universe

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   University of GroningenThe Effelsberg Bonn HI Survey EBHISKerp, J.; Winkle, B.; Kalberla, P.M.W.Published in:EPRINTS-BOOK-TITLEIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2009Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Kerp, J., Winkle, B., & Kalberla, P. M. W. (2009). The Effelsberg Bonn HI Survey EBHIS. In EPRINTS-BOOK-TITLE University of Groningen.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 04-06-2022arXiv:0910.1421v1  [astro-ph.GA]  8 Oct 2009The Effelsberg Bonn HI Survey EBHISJürgen Kerp ∗, Benjamin Winkel, Peter M.W. KalberlaArgelander-Institut für Astronomie, Universität BonnE-mail: jkerp@astro.uni-bonn.de,bwinkel@astro.uni-bonn.de,pkalberla@astro.uni-bonn.deThe Effelsberg-Bonn HI Survey (EBHIS) covers the whole sky north of Dec(2000)= −5◦ on afully sampled angular grid. Using state-of-the-art FPGA-spectrometers we perform a Milky Wayand an extragalactic HI survey in parallel. Moreover, the high dynamic range and short dumptime of the HI spectra allow to overcome the vast majority of all r dio-frequency-interference(RFI) events. The Milky Way data will be corrected for the stray-radiation bias which warrantsa main-beam efficiency of 99%. Towards the whole survey area we exceed the sensitivity limitof HIPASS, while towards the Sloan-Digital-Sky-Survey (SDS) area EBHIS offers an order ofmagnitude higher mass sensitivity. The Milky Way data will be a cornerstone for multi-frequencyastrophyics, while the extragalactic part will disclose detail d information on the structure forma-tion of the local universe.Panoramic Radio Astronomy: Wide-field 1-2 GHz research on galaxy evolution - PRA2009June 02 - 05 2009Groningen, the Netherlands∗Speaker.c© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licen. http://pos.sissa.it/The Effelsberg Bonn HI Survey EBHIS Jürgen Kerp1. The Effelsberg 21-cm multi-beam systemThe seven beam system was primarily optimized to perform Beam-P rk experiments. Usingthe Tracking and Imaging Radar (TIRA) telescope, space debris at an altitude of about 200 kmare illuminated. The Effelsberg multi-feed system receives the reflected signal of these space de-bris. Using the TIRA-Effelsberg combination space debris down to a linear size of 1 cm can beinvestigated [1].2. EBHIS conceptObserving time is expensive. Accordingly, we optimized EBHIS to provide valuable data fora broad scientific community. For this purpose, we decided touse the maximum of the availablebandwidth and FPGA-spectrometers to obtain high-quality data because of• short integration times of less than a second: this allows usto clean the data for the bulk ofthe RFI events, because they are variable in time, frequency, a d polarization.• an order of magnitude more spectral channels than classicalauto-correlators, this providesthe chance to map narrow spectral lines within a huge bandwidth range.The maximum EBHIS bandwidth is 100 MHz. The 14 FPGA spectrometers offer for eachpolarization 16.384 spectral channels, providing a corresponding velocity resolution of 1.3 kms−1.This is sufficiently narrow to resolve even the coldest CNM-structures belonging to the MilkyWay. The 0.5 sec integration time overcomes, in combinationwith the 8-bit dynamic range, eventhe strongest recorded RFI-events. Multiple coverages of the survey area will allow to correct forthe contribution of the stray-radiation received by the near and far side-lobes of the single dish.Applying a proper stray-radiation correction allows to reach n accuracy level equivalent to a 99%main-beam efficency. We are using frequency switch observations with 4 MHz frequency shift.The covered velocity range is -1000 to +20000kms−1.The extragalactic part of EBHIS is focused on the SLOAN-Digital Sky Survey (SDSS) area.Towards this region we expect to provide a scientifically significant contribution to studies of thelocal universe. The integration time of ten minutes per beamwill provide a mass sensitivity ofabout 107 M⊙ at the distance of the Virgo cluster. This will overcome the todays severe statisticallimitation of the HI-mass function towards the low-mass end. In comparison to the HIPASS [3],EBHIS offers a higher sensitivity because of a larger redshift range and a higher velocity resolutionacross the whole survey area down to Dec =−5◦. Towards the SDSS area we reach an order-of-magnitude higher sensitivity level than HIPASS.We observe five by five degrees fields. For the Milky Way survey wuse a scanning speedof four degrees per minute. Two coverages are sufficient to reach our final sensitivity limit for theMilky Way survey part accordingly. During the observationsthe feed orientation is permanentlyoptimized to warrant the full angular sampling. In regular time intervals we observe the standardposition S7 for an absolute calibration of our data. In betwen the noise-diode is used for relativecalibration. Test observations disclosed the stability ofthe whole receiving system lasting forseveral hours.2The Effelsberg Bonn HI Survey EBHIS Jürgen Kerp3. Science goalsEBHIS will address multiple scientific objectives. Here, wesk tch only a few major projects.For the Milky Way part we expect to make significant progress in case of halo studies. Studies ofhigh-velocity and intermediate-velocity clouds will allow to investigate their interaction with thedisk–halo interface [4]. Combining EBHIS data with absorption line measurements will disclosethe multi-phase/excitation structure of the high-altitude gas and allows to disclose their relationof Lyman-α systems at cosmological distances [2]. The high spectral and angular resolution incombination with the large survey area will allow for the first time to evaluate the rate at which tinyhalo structures appear to populate the lower galactic halo.In the near future, we expect that thesoft X-ray all-sky survey of eROSITA allows to detect the bulk of the local baryons by their diffusesoft X-ray emission. EBHIS and GASS (see Kalberla et al. these proceedings) will serve as majorresources to evaluate the amount of photoelectric absorption, which is in the order of 80% to 90%of the total X-ray flux of the warm-hot-intergalactic mediume ission.For the extragalactic part of EBHIS we will focus on the low-mass end of the HI mass spectrumof the local universe. The high sensitivity combined with our approved RFI-mitigation strategy willallow to derive highly statistical significant information. This will also improve our knowledge onthe local baryon budget as well as an evaluation of environmental effects on the HI properties ofgalaxies in general (see B. Winkel et al., these proceedings).4. EBHIS project statusDuring the first observing runs between Christmas 2008 and spring 2009 we spent all observ-ing time to selected areas. These areas were chosen to demonstrate the feasibility of the wholeEBHIS project. Accordingly, we focused i.e. on “classical”deep fields and high priority ob-jects. Starting in June 2009 we changed our observing strategy to perform the first coverage ofthe northern Milky Way sky. Figure 1 shows the present coverag (September 2009) of EBHIS.Figure 2 shows the Milky Way data quality after a quick-and-dirty data reduction, in particular noRFI-mitigation was performed.5. EBHIS performanceFigure 3 shows a position-velocity slice of an area towards the M81/M82-group. At a ra-dial velocity of about 750 kms−1 two galaxies have been detected. UGC 12732 is detected by theALFALFA survey [6], while NVSS J234508+260340 is not part ofthe ALFALFA catalog. Obvi-ously, EBHIS detected both galaxies at a high signal-to-noise level. The shown data comprise anet-observing time of four minutes per beam only.Figure 4 emphasizes the high velocity resolution of EBHIS thanks to the FGPA-spectrometersand their high number of spectral channels. The channel number is important with respect tothe RFI-mitigation because most RFI events are narrow in frequency accordingly only a smallportion of the galaxy rotation curve is affected. A comparison between the derived fluxes betweenALFALFA and EBHIS show a significant discrepancy. This is an open issue which we have tosolve in the near future.3The Effelsberg Bonn HI Survey EBHIS Jürgen KerpFigure 1: The plot shows the current (September 2009) coverage of the EBHIS survey. We observe five-by-five degree fields. Up to now fields of interest have been observed until June 2009 where we started the firstsystematic survey of the northern hemisphere. The map showsa RA-Dec projection with RA(2000)= 12hand Dec(2000)= 0◦ in the center.Figure 2: A channel map of the Milky Way sky displays a wealth of detailed structures. The shown EBHISMilky Way data are already fully calibrated, corrected for baseline and stray-radiation. RFI events are notremoved and cause artifacts at various positions across themap. However, their imprint does not severelydegrade the data quality.4The Effelsberg Bonn HI Survey EBHIS Jürgen KerpFigure 3: Position-velocity (PV) map towards the galaxy UGC 12732. The EBHIS data are fully calibratedand a baseline has been subtracted. The HI spectra show clearly the HI emission of the galaxy. The brightstripes across the PV-map show RFI events, the corresponding dark lines are their frequency-switch coun-terparts. The galaxy NVSS J234508+260340 next to UGC 12732 is also significantly detected but not partof the ALFALFA catalog of galaxies towards this area of interest.The EBHIS Milky Way survey will be finished within two years ofbserving time, assuming1000 hours of time per year. The extragalactic survey will need five years of observing time toreach its ultimate sensitivity limit.The EBHIS data will be distributed via an Internet interfacecomparable to the LAB survey[7]. In addition, we plan to provide data cubes for scientificuse.AcknowledgmentsThe authors thank the Deutsche Forschungsgemeinschaft (DFG) for financial support underthe research grant KE757/7-1. Based on observations with the 100-m telescope of the MPIfR(Max-Planck-Institut für Radioastronomie) at Effelsberg.References[1] D. Banka, L. Leushacke, D. Mehrholz,Beam-Park-Experiment 1/2000 with TIRA, Space Debris2 83[2] N. Ben Bekhti, P. Richter, B. Winkel, F. Kenn, T. Westmeier, High-resolution 21-cm observations oflow-column density gas clumps in the Milky Way Halo,A&A 503 483[3] D.G. Barnes, L. Staveley-Smith, W.J.G. de Blok, et al.,The HI Parkes All Sky Survey: southernobservations, calibration and robuts imaging, MNRAS322 4865The Effelsberg Bonn HI Survey EBHIS Jürgen KerpFigure 4: EBHIS HI spectrum of UGC 12732. The spectrum shows the quality of the HI data obtained.The integration time for this spectrum was 4 minutes. Applying our RFI-mitigation and increasing the netobserving time towards the SDSS area will provide a unique data b se for studies of the local universe.[4] P.M.W. Kalberla, J. Kerp,The HI Distribution of the Milky Way, ARA&A47 27[5] J. Kerp,HI - the window to the early universe in X-rays, AN 324 69[6] R. Giovanelli, M.P. Haynes, B.R. Kent, et al.,The Arecibo Legacy Fast ALFA Survey. I. ScienceGoals, Survey Design, and Strategy, AJ 130 2598[7] P.M.W. Kalberla, W.B. Burton, D. Hartmann et al.,The Leiden/Argentine/Bonn (LAB) Survey of theGalactic HI. Final data release of the combined LDS and IAR surveys with improved stray-radiationcorrections, A&A 440 7756

The Effelsberg Bonn HI Survey EBHIS

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The Effelsberg Bonn HI Survey EBHIS

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