Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole

S. Yatawatta; A.G. de Bruyn; M.A. Brentjens; P. Labropoulos; V.N. Pandey; S. Kazemi; S. Zaroubi; L.V.E Koopmans; A.R. Offringa; V. Jelic; O. Martinez Rubi; V. Veligatla; S.J. Wijnholds; W.N. Brouw; G. Bernardi; B. Ciardi; S. Daiboo; G. Harker; G. Mellema; J. Schaye; R. Thomas; H. Vedantham; E. Chapman; F.B. Abdalla; A. Alexov; J. Anderson; I.M. Avruch; F. Batejat; M.E. Bell; M.R. Bell; Marinus Jan Bentum; P. Best; A. Bonafede; J. Bregman; F. Breitling; R.H. van de Brink; J.W. Broderick; M. Brüggen; J. Conway; F. de Gasperin; E. de Geus; S. Duscha; H. Falcke; R.A. Fallows; C. Ferrari; W. Frieswijk; M.A. Garrett; J.M. Griessmeier; A.W. Gunst; T.E. Hassall; J.W.T. Hessels; M. Hoeft; M. Iacobelli; E. Juette; A. Karastergiou; V.I. Kondratiev; M. Kramer; M. Kuniyoshi; G. Kuper; J. van Leeuwen; P. Maat; G. Mann; J.P. McKean; M. Mevius; J.D. Mol; H. Munk; R. Nijboer; J.E. Noordam; M.J. Norden; E. Orrú; H. Paas; M. Pandey-Pommier; R. Pizzo; A.G. Polatidis; W. Reich; H.J.A. Röttgering; J. Sluman; O. Smirnov; B. Stappers; M. Steinmetz; M. Tagger; Y. Tang; C. Tasse; S. ter Veen; R. Vermeulen; R.J. van Weeren; M. Wise; O. Wucknitz; P. Zarka

doi:10.1051/0004-6361/201220874

Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole

S. Yatawatta, A.G. de Bruyn, M.A. Brentjens, P. Labropoulos, V.N. Pandey, S. Kazemi, S. Zaroubi, L.V.E Koopmans, A.R. Offringa, V. Jelic, O. Martinez Rubi, V. Veligatla, S.J. Wijnholds, W.N. Brouw, G. Bernardi, B. Ciardi, S. Daiboo, G. Harker, G. Mellema, J. SchayeR. Thomas, H. Vedantham, E. Chapman, F.B. Abdalla, A. Alexov, J. Anderson, I.M. Avruch, F. Batejat, M.E. Bell, M.R. Bell, Marinus Jan Bentum, P. Best, A. Bonafede, J. Bregman, F. Breitling, R.H. van de Brink, J.W. Broderick, M. Brüggen, J. Conway, F. de Gasperin, E. de Geus, S. Duscha, H. Falcke, R.A. Fallows, C. Ferrari, W. Frieswijk, M.A. Garrett, J.M. Griessmeier, A.W. Gunst, T.E. Hassall, J.W.T. Hessels, M. Hoeft, M. Iacobelli, E. Juette, A. Karastergiou, V.I. Kondratiev, M. Kramer, M. Kuniyoshi, G. Kuper, J. van Leeuwen, P. Maat, G. Mann, J.P. McKean, M. Mevius, J.D. Mol, H. Munk, R. Nijboer, J.E. Noordam, M.J. Norden, E. Orrú, H. Paas, M. Pandey-Pommier, R. Pizzo, A.G. Polatidis, W. Reich, H.J.A. Röttgering, J. Sluman, O. Smirnov, B. Stappers, M. Steinmetz, M. Tagger, Y. Tang, C. Tasse, S. ter Veen, R. Vermeulen, R.J. van Weeren, M. Wise, O. Wucknitz, P. Zarka

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Abstract

The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP.

Original language	Undefined
Pages (from-to)	1-19
Number of pages	19
Journal	Astronomy & astrophysics
Volume	550
Issue number	A136
DOIs	https://doi.org/10.1051/0004-6361/201220874
Publication status	Published - 14 Jan 2013

Keywords

diffuse radiation
reionization
IR-89500
Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations
METIS-302720
EWI-24509

Access to Document

10.1051/0004-6361/201220874

http://eprints.eemcs.utwente.nl/secure2/24509/01/1301.1630v2.pdf

Cite this

Yatawatta, S., de Bruyn, A. G., Brentjens, M. A., Labropoulos, P., Pandey, V. N., Kazemi, S., Zaroubi, S., Koopmans, L. V. E., Offringa, A. R., Jelic, V., Martinez Rubi, O., Veligatla, V., Wijnholds, S. J., Brouw, W. N., Bernardi, G., Ciardi, B., Daiboo, S., Harker, G., Mellema, G., ... Zarka, P. (2013). Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole. Astronomy & astrophysics, 550(A136), 1-19. https://doi.org/10.1051/0004-6361/201220874

@article{25f0cf548af8464d85139261fe0e6752,

title = "Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole",

abstract = "The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP.",

keywords = "diffuse radiation, reionization, IR-89500, Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations, METIS-302720, EWI-24509",

author = "S. Yatawatta and {de Bruyn}, A.G. and M.A. Brentjens and P. Labropoulos and V.N. Pandey and S. Kazemi and S. Zaroubi and L.V.E Koopmans and A.R. Offringa and V. Jelic and {Martinez Rubi}, O. and V. Veligatla and S.J. Wijnholds and W.N. Brouw and G. Bernardi and B. Ciardi and S. Daiboo and G. Harker and G. Mellema and J. Schaye and R. Thomas and H. Vedantham and E. Chapman and F.B. Abdalla and A. Alexov and J. Anderson and I.M. Avruch and F. Batejat and M.E. Bell and M.R. Bell and Bentum, {Marinus Jan} and P. Best and A. Bonafede and J. Bregman and F. Breitling and {van de Brink}, R.H. and J.W. Broderick and M. Br{\"u}ggen and J. Conway and {de Gasperin}, F. and {de Geus}, E. and S. Duscha and H. Falcke and R.A. Fallows and C. Ferrari and W. Frieswijk and M.A. Garrett and J.M. Griessmeier and A.W. Gunst and T.E. Hassall and J.W.T. Hessels and M. Hoeft and M. Iacobelli and E. Juette and A. Karastergiou and V.I. Kondratiev and M. Kramer and M. Kuniyoshi and G. Kuper and {van Leeuwen}, J. and P. Maat and G. Mann and J.P. McKean and M. Mevius and J.D. Mol and H. Munk and R. Nijboer and J.E. Noordam and M.J. Norden and E. Orr{\'u} and H. Paas and M. Pandey-Pommier and R. Pizzo and A.G. Polatidis and W. Reich and H.J.A. R{\"o}ttgering and J. Sluman and O. Smirnov and B. Stappers and M. Steinmetz and M. Tagger and Y. Tang and C. Tasse and {ter Veen}, S. and R. Vermeulen and {van Weeren}, R.J. and M. Wise and O. Wucknitz and P. Zarka",

note = "eemcs-eprint-24509 ",

year = "2013",

month = jan,

day = "14",

doi = "10.1051/0004-6361/201220874",

language = "Undefined",

volume = "550",

pages = "1--19",

journal = "Astronomy & astrophysics",

issn = "0004-6361",

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Yatawatta, S, de Bruyn, AG, Brentjens, MA, Labropoulos, P, Pandey, VN, Kazemi, S, Zaroubi, S, Koopmans, LVE, Offringa, AR, Jelic, V, Martinez Rubi, O, Veligatla, V, Wijnholds, SJ, Brouw, WN, Bernardi, G, Ciardi, B, Daiboo, S, Harker, G, Mellema, G, Schaye, J, Thomas, R, Vedantham, H, Chapman, E, Abdalla, FB, Alexov, A, Anderson, J, Avruch, IM, Batejat, F, Bell, ME, Bell, MR, Bentum, MJ, Best, P, Bonafede, A, Bregman, J, Breitling, F, van de Brink, RH, Broderick, JW, Brüggen, M, Conway, J, de Gasperin, F, de Geus, E, Duscha, S, Falcke, H, Fallows, RA, Ferrari, C, Frieswijk, W, Garrett, MA, Griessmeier, JM, Gunst, AW, Hassall, TE, Hessels, JWT, Hoeft, M, Iacobelli, M, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, van Leeuwen, J, Maat, P, Mann, G, McKean, JP, Mevius, M, Mol, JD, Munk, H, Nijboer, R, Noordam, JE, Norden, MJ, Orrú, E, Paas, H, Pandey-Pommier, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Sluman, J, Smirnov, O, Stappers, B, Steinmetz, M, Tagger, M, Tang, Y, Tasse, C, ter Veen, S, Vermeulen, R, van Weeren, RJ, Wise, M, Wucknitz, O & Zarka, P 2013, 'Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole', Astronomy & astrophysics, vol. 550, no. A136, pp. 1-19. https://doi.org/10.1051/0004-6361/201220874

TY - JOUR

T1 - Initial deep LOFAR observations of epoch of reionization windows: I. The north celestial pole

AU - Yatawatta, S.

AU - de Bruyn, A.G.

AU - Brentjens, M.A.

AU - Labropoulos, P.

AU - Pandey, V.N.

AU - Kazemi, S.

AU - Zaroubi, S.

AU - Koopmans, L.V.E

AU - Offringa, A.R.

AU - Jelic, V.

AU - Martinez Rubi, O.

AU - Veligatla, V.

AU - Wijnholds, S.J.

AU - Brouw, W.N.

AU - Bernardi, G.

AU - Ciardi, B.

AU - Daiboo, S.

AU - Harker, G.

AU - Mellema, G.

AU - Schaye, J.

AU - Thomas, R.

AU - Vedantham, H.

AU - Chapman, E.

AU - Abdalla, F.B.

AU - Alexov, A.

AU - Anderson, J.

AU - Avruch, I.M.

AU - Batejat, F.

AU - Bell, M.E.

AU - Bell, M.R.

AU - Bentum, Marinus Jan

AU - Best, P.

AU - Bonafede, A.

AU - Bregman, J.

AU - Breitling, F.

AU - van de Brink, R.H.

AU - Broderick, J.W.

AU - Brüggen, M.

AU - Conway, J.

AU - de Gasperin, F.

AU - de Geus, E.

AU - Duscha, S.

AU - Falcke, H.

AU - Fallows, R.A.

AU - Ferrari, C.

AU - Frieswijk, W.

AU - Garrett, M.A.

AU - Griessmeier, J.M.

AU - Gunst, A.W.

AU - Hassall, T.E.

AU - Hessels, J.W.T.

AU - Hoeft, M.

AU - Iacobelli, M.

AU - Juette, E.

AU - Karastergiou, A.

AU - Kondratiev, V.I.

AU - Kramer, M.

AU - Kuniyoshi, M.

AU - Kuper, G.

AU - van Leeuwen, J.

AU - Maat, P.

AU - Mann, G.

AU - McKean, J.P.

AU - Mevius, M.

AU - Mol, J.D.

AU - Munk, H.

AU - Nijboer, R.

AU - Noordam, J.E.

AU - Norden, M.J.

AU - Orrú, E.

AU - Paas, H.

AU - Pandey-Pommier, M.

AU - Pizzo, R.

AU - Polatidis, A.G.

AU - Reich, W.

AU - Röttgering, H.J.A.

AU - Sluman, J.

AU - Smirnov, O.

AU - Stappers, B.

AU - Steinmetz, M.

AU - Tagger, M.

AU - Tang, Y.

AU - Tasse, C.

AU - ter Veen, S.

AU - Vermeulen, R.

AU - van Weeren, R.J.

AU - Wise, M.

AU - Wucknitz, O.

AU - Zarka, P.

N1 - eemcs-eprint-24509

PY - 2013/1/14

Y1 - 2013/1/14

N2 - The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP.

AB - The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP.

KW - diffuse radiation

KW - reionization

KW - IR-89500

KW - Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations

KW - METIS-302720

KW - EWI-24509

U2 - 10.1051/0004-6361/201220874

DO - 10.1051/0004-6361/201220874

M3 - Article

SN - 0004-6361

VL - 550

SP - 1

EP - 19

JO - Astronomy & astrophysics

JF - Astronomy & astrophysics

IS - A136

ER -