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On sky characterization of the BAORadio wide band digital backend: Search for HI emission in Abell85, Abell1205 and Abell2440 galaxy clusters | | R. Ansari
; J.E Campagne
; P. Colom
; C. Ferrari
; Ch. Magneville
; J.M. Martin
; M. Moniez
; A.S. Torrento
; | | Date: |
11 May 2015 | | Abstract: | We have observed regions of three galaxy clusters at z$sim$ [0.06, 0.09]
(Abell85, Abell1205, Abell2440), as well as calibration sources with the Nancay
radiotelescope (NRT) to search for 21 cm emission and fully characterize the
FPGA based BAORadio digital backend. The total observation time of few hours
per source have been distributed over few months, from March 2011 to January
2012, due to scheduling constraints of the NRT, which is a transit telescope.
Data have been acquired in parallel with the NRT standard correlator (ACRT)
back-end, as well as with the BAORadio data acquisition system. The latter
enables wide band instantaneous observation of the [1250, 1500]MHz frequency
range, as well as the use of powerful RFI mitigation methods thanks to its fine
time sampling. A number of questions related to instrument stability, data
processing and calibration are discussed. We have obtained the radiometer
curves over the integration time range [0.01,10 000] seconds and we show that
sensitivities of few mJy over most of the wide frequency band can be reached
with the NRT.
It is clearly shown that in blind line search, which is the context of HI
intensity mapping for Baryon Acoustic Oscillations, the new acquisition system
and processing pipeline outperforms the standard one. We report a positive
detection of 21 cm emission at 3 sigma-level from galaxies in the outer region
of Abell85 at 1352 MHz (14 400 km/s) corresponding to a line strength of 0.8 Jy
km/s. We observe also an excess power around 1318 MHz (21 600 km/s), although
at lower statistical significance, compatible with emission from Abell1205
galaxies. Detected radio line emissions have been cross matched with optical
catalogs and we have derived hydrogen mass estimates. | | Source: | arXiv, 1505.2623 | | Services: | Forum | Review | PDF | Favorites | |
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