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J/AJ/130/2613     The Arecibo Legacy Fast ALFA survey. II    (Giovanelli+, 2005)

The Arecibo Legacy Fast ALFA survey. II. Results of precursor observations. Giovanelli R., Haynes M.P., Kent B.R., Perillat P., Catinella B., Hoffman G.L., Momjian E., Rosenberg J.L., Saintonge A., Spekkens K., Stierwalt S., Brosch N., Masters K.L., Springob C.M., Karachentsev I.D., Karachentseva V.E., Koopmann R.A., Muller E., van Driel W., van Zee L. <Astron. J., 130, 2613-2624 (2005)> =2005AJ....130.2613G
ADC_Keywords: H I data Keywords: galaxies: distances and redshifts - galaxies: halos - galaxies: luminosity function, mass function - galaxies: photometry - galaxies: spiral - radio lines: galaxies Abstract: In preparation for the full Arecibo Legacy Fast ALFA (ALFALFA) extragalactic HI survey, precursor observations were carried out in 2004 August-September with the seven-beam Arecibo L-band Feed Array (ALFA) receiver system and the Wideband Arecibo Pulsar Processor spectral processors. While these observations were geared mainly at testing and debugging survey strategy, hardware, and software, approximately 48hr of telescope time yielded science-quality data. To test our ability to discriminate cosmic signals from radio-frequency interference and noise, 165 candidates ranging in reliability likelihood were reobserved with the single-beam L-band wide system at Arecibo in 2005 January-February. Of those, 41% were confirmed as real. We present the results of both the ALFA and the single-beam observations for the sample of 166 confirmed HI sources, as well as our assessment of their optical counterparts. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 71 166 Parameters of ALFA (L-band Feed Array) detections table3.dat 77 68 *Parameters of LBW (L-band wide) detections table4.dat 66 166 Optical ID, distances and HI masses notes.dat 80 171 Notes
Note on table3.dat : HI 010225.7+263613 is a misprint for HI 010225.7+263713.
See also: VIII/73 : HI Parkes All Sky Survey Catalogue (HIPASS) (Meyer+, 2004) J/MNRAS/342/738 : HI Jodrell All Sky Survey (Lang+, 2003) J/ApJS/130/177 : Arecibo Dual-Beam Survey (Rosenberg+, 2000) J/AJ/133/2569 : Arecibo legacy fast ALFA survey III. (Giovanelli+, 2007) J/AJ/135/588 : Arecibo legacy fast ALFA survey V. (Saintonge+, 2008) J/AJ/136/713 : Arecibo legacy fast ALFA survey. VI. (Kent+, 2008) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HI] 4- 18 A15 --- HI Source identification (G1) 20- 23 F4.1 s e_RA ? Estimated Right Ascension centroid position error 25- 26 I2 arcsec e_DE ? Estimated Declination centroid position error 28- 32 I5 km/s cz Center heliocentric velocity of the feature 34- 35 I2 km/s e_cz Estimated measurement error in cz 37- 38 I2 km/s ecz Systematic component error in cz (G2) 40- 42 I3 km/s W ? Velocity width of spectral feature (G3) 44- 46 I3 km/s e_W ? Estimated error in W (G4) 48- 51 F4.2 mJy rms RMS of composite HI spectrum (G5) 53- 57 F5.2 Fc Spectral feature flux integral 59- 62 F4.2 e_Fc Statistical error in Fc (G6) 64- 68 F5.2 Fm ? Spectral feature flux integral obtained from map (1) 70 A1 --- LBW [L] detection corroborated with LBW (2) 71 A1 --- Note [*] Additional notes detailed in notes.dat
Note (1): For cases for which the ALFA data indicate significant angular extent of the HI source, this is an estimate of the total flux of the source derived from a map. Note that for the majority of sources the signal-to-noise ratio is not sufficient to obtain a reliable map. Note (2): the 'L' indicates that the ALFA detection is corroborated by observations with the LBW single-pixel feed. The results of those observations are given in Table 3.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HI] 4- 18 A15 --- HI Source identification (G1) 20- 21 I2 h RAh Hour of Right Ascension (J2000) 23- 24 I2 min RAm Minute of Right Ascension (J2000) 26- 29 F4.1 s RAs Second of Right Ascension (J2000) 31 A1 --- DE- Sign of the Declination (J2000) 32- 33 I2 deg DEd Degree of Declination (J2000) 35- 36 I2 arcmin DEm Arcminute of Declination (J2000) 38- 39 I2 arcsec DEs Arcsecond of Declination (J2000) 41- 45 I5 km/s cz Center heliocentric velocity of the feature 47- 48 I2 km/s e_cz Estimated measurement error in cz 50- 52 I3 km/s ecz Systematic component of error in cz (G2) 54- 56 I3 km/s W Velocity width of spectral feature (G3) 58- 60 I3 km/s e_W Estimated error in W (G4) 62- 65 F4.2 mJy rms RMS of LBW HI spectrum (G5) 67- 70 F4.2 Fc Spectral feature flux integral 72- 75 F4.2 e_Fc Statistical error in Fc (G6) 77 A1 --- Note [*] Indicates comments available in notes.dat
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HI] 4- 18 A15 --- HI Source identification (G1) 20- 25 I6 --- AGC Arecibo General Catalog identification (1) 27- 28 I2 h RAo.h ? Hour of Right Ascension (J2000) (2) 30- 31 I2 min RAo.m ? Minute of Right Ascension (J2000) (2) 33- 36 F4.1 s RAo.s ? Second of Right Ascension (J2000) (2) 38 A1 --- DEo.- Sign of the Declination (J2000) (2) 39- 40 I2 deg DEo.d ? Degree of Declination (J2000) (2) 42- 43 I2 arcmin DEo.m ? Arcminute of Declination (J2000) (2) 45- 46 I2 arcsec DEo.s ? Arcsecond of Declination (J2000) (2) 48- 52 F5.1 Mpc Dcmb ? CMB distance assuming pure Hubble flow (3) 54- 58 F5.1 Mpc Dpec Distance corrected for peculiar velocity (4) 60- 64 F5.2 [solMass] MHI Log of the HI mass (5) 66 A1 --- Note [*] Indicates comments available in notes.dat
Note (1): AGC numbers smaller than 13000 coincide with those of the Uppsala General Catalog (Nilson 1973, Cat. VII/26). Note (2): Of the proposed optical counterpart of the HI source. These coordinates are either obtained from previous tabulations or directly measured using the Skyview facility. Positional accuracies are of order 1". Note (3): Obtained from the radial velocity corrected to the Cosmic Microwave Background rest frame, and assuming pure Hubble flow with H0=70km/s/Mpc. Note (4): Obtained from the measured redshift and from the peculiar velocity field model of Tonry et al. (2000ApJ...530...62G), for H0=70km/s/Mpc. In addition to the error on the measurement of cz and the systematics in the flow model (see Masters, 2005, Ph.D. thesis, Cornell Univ.), a "thermal" velocity component of 187km/s as assumed by Tonry et al. (2000ApJ...530...62G) introduces an additional uncertainty of 2.7Mpc on each distance estimate. Note (5): Via MHI=2.356x105Dpec2F, where Dpec is the distance in Mpc and F is the flux integral obtained from Fm (or Fc if Fm is blank) of Table 2.
Byte-by-byte Description of file: notes.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [HI] 4- 18 A15 --- HI Source identification 20- 80 A61 --- Note Note
Global Notes: Note (G1): Source identification, composed of the qualifier 'HI' and the RA and DE (epoch J2000.0) of the HI centroid. Note (G2): When two non zero numbers are listed for e_cz and f_cz, the second is an estimate of the systematic component of the error, while the first is a statistical error which depends on the shape of the signal and the signal-to-noise. The systematic error results from the observer's subjective choice of the signal boundaries: when those are clear, the systematic error is nil; when strong uncertainty exists in making that choice, a visual guess is made by the observer of the potential amplitude of the uncertainty. The total error on cz is the sum in quadrature of the two components of the error. Note (G3): Measured at 50% level of intensity of two peaks on each side of the signal. Widths are corrected for instrumental smoothing and relativistic broadening, i.e. the tabulated values are (Wmeasured2-res2)-1/2/(1+z), where res is the spectral resolution in km/s. No disk inclination nor turbulent motion correction is applied to the widths. Note (G4): Note that the measurement error on the width is effectively a fractional error, so that W(e_W)=100(50) should be read as 100+50-33. Note (G5): Measured "locally", i.e. over a baseline region within 10MHz of the detected feature rather than over the full spectrum. Note (G6): Compounded with the overall uncertainty on the flux calibration. This value is an underestimate of the true flux if the source is extended in comparison with the beam size.
History: From electronic version of the journal References: Giovanelli et al., Paper I 2005AJ....130.2598G
(End) Greg Schwarz [AAS], Marianne Brouty [CDS] 04-Aug-2006
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