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J/ApJ/507/655       VI photometry of new Cepheids in NGC 2541 (Ferrarese+, 1998)

The Hubble Space Telescope Key Project on the extragalactic distance scale. XII. The discovery of cepheids and a new distance to NGC 2541. Ferrarese L., Bresolin F., Kennicutt R.C.Jr, Saha A., Stetson P.B., Freedman W.L., Mould J.R., Madore B.F., Sakai S., Ford H.C., Gibson B.K., Graham J.A., Han M., Hoessel J.G., Huchra J., Hughes S.M., Illingworth G.D., Phelps R., Prosser C.F., Silbermann N.A. <Astrophys. J. 507, 655 (1998)> =1998ApJ...507..655F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry Mission_Name: HST Keywords: Cepheids - galaxies: distances and redshifts - galaxies: individual (NGC 2541) Abstract: We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). A total of 25 exposures (divided into 13 epochs) were obtained using the F555W filter (transformed to Johnson V), and nine exposures were obtained (divided into five epochs) using the F814W filter (transformed to Cousins I). Photometric reduction of the data is performed using two independent packages, DoPHOT and DAOPHOT II/ALLFRAME, which give very good agreement in the measured magnitudes. A total of 34 bona fide Cepheids, with periods ranging from 12 to over 60 days, are identified based on both sets of photometry. By fitting V and I period-luminosity relations, apparent distance moduli are derived assuming a Large Magellanic Cloud distance modulus and mean color excess of µLMC=18.50±0.10mag and E(B-V)=0.10mag, respectively. Adopting A(V)/E(V-I)=2.45, we obtain a true distance modulus to NGC 2541 of µ0=30.47±0.11 (random) ±0.12 (systematic) mag (D=12.4±0.6 [random] ±0.7 [systematic] Mpc), and a total (Galactic plus internal) mean color excess E(B-V)=0.08±0.05 (internal error) mag. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table5.dat 46 34 Astrometry for the NGC 2541 Cepheids table6.dat 26 437 V (F555W) photometry for NGC 2541 Cepheids table7.dat 26 159 I (F814W) photometry for NGC 2541 Cepheids table8.dat 79 34 DOPHOT mean photometry of the NGC 2541 Cepheids table9.dat 79 34 Allframe mean photometry of the NGC 2541 Cepheids table12.dat 46 23 Astrometry for other NGC 2541 variable candidates table13.dat 26 297 V photometry for other NGC 2541 variable candidates table14.dat 26 106 I photometry for other NGC 2541 variable candidates table15.dat 79 22 DOPHOT mean photometry of other NGC 2541 variables table16.dat 79 11 Allframe mean photometry of other NGC 2541 variables table17.dat 71 24 Photometry for the PC secondary standards table18.dat 71 29 Photometry for the WF2 secondary standards table19.dat 71 32 Photometry for the WF3 secondary standards table20.dat 71 29 Photometry for the WF4 secondary standards note5.dat 80 44 Individual notes on Cepheids note12.dat 80 46 Individual notes on other variable stars
See also: J/ApJ/463/26 : Extragalactic Distance Scale Key Project. III (Kelson+ 1996) J/ApJ/508/491 : M101 Cepheids (Stetson+, 1998) J/ApJ/521/155 : New Cepheids and distance to NGC 4535 (Macri+, 1999) J/ApJ/523/540 : VI photometry of new Cepheids in NGC 3319 (Sakai+, 1999) J/ApJ/529/723 : VI photometry of Cepheids (Gibson+, 2000) Byte-by-byte Description of file: table5.dat table12.dat
Bytes Format Units Label Explanations
1- 3 A3 --- [FBK98] Identification (CNN or VNN) (1) 5- 10 F6.2 pix Xpos X position (2) 12- 17 F6.2 pix Ypos Y position (2) 19- 20 I2 h RAh Right ascension (J2000) (3) 22- 23 I2 min RAm Right ascension (J2000) (3) 25- 29 F5.2 s RAs Right ascension (J2000) (3) 31 A1 --- DE- Declination sign (J2000) 32- 33 I2 deg DEd Declination (J2000) (3) 35- 36 I2 arcmin DEm Declination (J2000) (3) 38- 41 F4.1 arcsec DEs Declination (J2000) (3) 43- 46 A4 --- Chip Chip (PC, WF 2, WF 3, WF 4)
Note (1): CNN for Cepheids stars, VNN for other variable stars Note (2): The X- and Y-coordinates are relative to the 1995 October 30 epoch. For each 800 x 800 pixels chip, pixel [1, 1] is located at the edge of the pyramid. Note (3): RA and DE are calculated using the IRAF task STSDAS.HST CALIB.WFPC.METRIC, version 1.3.5 (1996 July).
Byte-by-byte Description of file: table[67].dat table1[34].dat
Bytes Format Units Label Explanations
1- 3 A3 --- [FBK98] Identification (CNN or VNN) 5- 15 F11.3 d HJD Heliocentric Julian date 17- 21 F5.2 mag mag V or I magnitude 23- 26 F4.2 mag e_mag rms uncertainty on mag
Byte-by-byte Description of file: table[89].dat table1[56].dat
Bytes Format Units Label Explanations
1- 3 A3 --- [FBK98] Identification (CNN or VNN) 5 A1 --- l_Per Limit flag on Per 6- 9 F4.1 d Per Period 11 A1 --- l_Per2 Limit flag on Per2 12- 13 I2 d Per2 ? Upper limit for period interval 15- 19 F5.2 mag F555Wph Phase-weighted mean F555W magnitude 21- 25 F5.2 mag F555Wav Intensity-averaged mean F555W magnitude 27- 31 F5.2 mag F814Wph ? Phase-weighted mean F814W magnitude 33- 37 F5.2 mag F814WphCor ? Correction adopted for F814Wph (1) 39- 43 F5.2 mag F814Wav ? Intensity-average mean F814W magnitude 45- 49 F5.2 mag F814WavCor ? Correction adopted for F814Wav (1) 51- 55 F5.2 mag Vmagph ? Phase-weighted mean V magnitude 57- 61 F5.2 mag Vmagav ? Intensity-averaged mean V magnitude 63- 67 F5.2 mag Imagph ? Phase-weighted mean I magnitude 69- 73 F5.2 mag Imagav ? Intensity-averaged mean I magnitude 75- 79 F5.2 --- chi2/sigma ? Reduced ξ2r value for DoPHOT or σ for ALLFRAME
Note (1): Value of the magnitude correction applied to the F814W magnitudes, defined as in section 4.4 of the paper.
Byte-by-byte Description of file: table1[789].dat table20.dat
Bytes Format Units Label Explanations
1- 6 F6.2 pix Xpos X position (1) 8- 13 F6.2 pix Ypos Y position (1) 15- 16 I2 h RAh Right ascension (J2000) (2) 18- 19 I2 min RAm Right ascension (J2000) (2) 21- 25 F5.2 s RAs Right ascension (J2000) (2) 27 A1 --- DE- Declination sign (J2000) (2) 28- 29 I2 deg DEd Declination (J2000) (2) 31- 32 I2 arcmin DEm Declination (J2000) (2) 34- 37 F4.1 arcsec DEs Declination (J2000) (2) 39- 43 F5.2 mag F555W F555W magnitude(3) 45- 48 F4.2 mag e_F555W rms uncertainty on F555W 50- 54 F5.2 mag F814W F814W magnitude (3) 56- 59 F4.2 mag e_F814W rms uncertainty on F814W 61- 65 F5.2 mag Vmag V magnitude (4) 67- 71 F5.2 mag Imag I magnitude (4)
Note (1): The X and Y coordinate are relative to the 1995 October 30 epoch. For each 800x800 pixels chip, pixel [1,1] is located at the edge of the WFPC2 pyramid Note (2): RA and DE are calculated using the IRAF task STSDAS.HST_CALIB.WFPC.METRIC, version 1.3.5 (July 1996) Note (3): F555W and F814W instrumental magnitudes are intensity averaged over 13 and 5 epochs respectively. Note (4): V and I magnitudes are calculated from the instrumental F555W and F814W magnitudes as described in section 3 of the paper.
Byte-by-byte Description of file: note5.dat note12.dat
Bytes Format Units Label Explanations
1- 3 A3 --- [FBK98] Identification (CNN or VNN) 5- 80 A76 --- Note Text of the note (1)
Note (1): The term "isolated" is use d for stars for which no companions are identified within a 3 pixel radius.
Acknowledgements: From ApJ electronic version References: Freedman et al., Paper I 1994ApJ...427..628F Hughes et al., Paper II 1994ApJ...428..143H Kelson et al., Paper III 1996ApJ...463...26K, Cat. J/ApJ/463/26 Ferrarese et al., Paper IV 1996ApJ...464..568F Hill et al., Paper V 1998ApJ...496..648H Silbermann et al., Paper VI 1996ApJ...470....1S Graham et al., Paper VII 1997ApJ...477..535G Rawson et al., Paper VIII 1997ApJ...490..517R Phelps et al., Paper IX 1998ApJ...500..763P Hughes et al. Paper X 1998ApJ...501...32H Turner et al., Paper XI 1998ApJ...505..207T Kennicutt et al., Paper XIII 1998ApJ...498..181K Silbermann et al., Paper XIV 1999ApJ...515....1S Madore et al., Paper XV 1999ApJ...515...29M Stetson et al., Paper XVI 1998ApJ...508..491S Gibson et al., Paper XVII 1999ApJ...512...48G Macri et al., Paper XVIII 1999ApJ...521..155M, Cat. J/ApJ/521/155 Kelson et al., Paper XIX 1999ApJ...514..614K Graham et al., Paper XX 1999ApJ...516..626G Mould et al., Paper XXI 2000ApJ...528..655M Prosser et al., Paper XXII 1999ApJ...525...80P Sakai et al., Paper XXIII 1999ApJ...523..540S, Cat. J/ApJ/523/540 Sakai et al. Paper XXIV 2000ApJ...529..698S Gibson et al., Paper XXV 2000ApJ...529..723G, Cat. J/ApJ/529/723 Ferrarese et al. Paper XXVI 2000ApJ...529..745F Kelson et al. Paper XXVII 2000ApJ...529..768K Mould et al. Paper XXVIII 2000ApJ...529..786M
(End) Patricia Bauer [CDS] 09-Mar-1999
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