J/AJ/149/183 gri photometry of variables in NGC 4258 (Hoffmann+, 2015)
Cepheid variables in the maser-host galaxy NGC 4258.
Hoffmann S.L., Macri L.M.
<Astron. J., 149, 183 (2015)>
=2015AJ....149..183H 2015AJ....149..183H
ADC_Keywords: Galaxies, nearby ; Stars, variable ; Stars, population II ;
Photometry, ugriz ; Cross identifications
Keywords: distance scale - galaxies: individual: NGC 4258 -
stars: variables: Cepheids
Abstract:
We present results of a ground-based survey for Cepheid variables in
NGC4258. This galaxy plays a key role in the Extragalactic Distance
Scale due to its very precise and accurate distance determination via
very long baseline interferometry observations of water masers. We
imaged two fields within this galaxy using the Gemini North telescope
and the Gemini Multi-Object Spectrograph, obtaining 16 epochs of data
in the Sloan Digital Sky Survey gri bands over 4yr. We carried out
point-spread function photometry and detected 94 Cepheids with periods
between 7 and 127 days, as well as an additional 215 variables which
may be Cepheids or Population II pulsators. We used the Cepheid sample
to test the absolute calibration of theoretical gri Period-Luminosity
relations and found good agreement with the maser distance to this
galaxy. The expected data products from the Large Synoptic Survey
Telescope should enable Cepheid searches out to at least 10Mpc.
Description:
We conducted the Cepheid search using the Gemini North 8.1m telescope
and the Gemini Multi-Object Spectrograph (GMOS). GMOS has a 5.5'*5.5'
field of view that is covered by three charged-coupled devices (CCDs)
with a scale of 0.0727"/pixel. NGC 4258 was imaged on 22 nights over
4yr (2004: Feb 18, Feb 20, Mar 29, May 22, May 24, Jul 08, Jul 14;
2005: Feb 10, Mar 09, Apr 09, Apr 12, May 04, May 08; 2007: Feb 22,
Apr 07, Apr 12, Apr 20; 2008: Jan 06-07, Jan 10, Jan 16, Feb 16). We
used the SDSS gri filters. The seeing was below 0.7"
In order to perform a photometric calibration of the Gemini data,
additional observations were obtained with the 3.5m WIYN telescope at
Kitt Peak National Observatory using the MiniMosaic camera. Its field
of view of 9.6'*9.6' is covered by 2 CCDs. The camera was used in 2*2
binned mode, which yields an effective scale of 0.28"/pixel. We
observed ten fields covering NGC 4258 at three different epochs (one
night per lunation for three consecutive months) using SDSS gri
filters (Kitt Peak filter numbers k1017, k1018, k1019).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 54 409 Secondary standards
table6.dat 92 94 NGC 4258 Cepheids
table7.dat 92 215 NGC 4258 variables
table8.dat 31 22664 Light curve data
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/AJ/149/117 : LMC infrared survey. I. Photometry of Cepheids (Macri+, 2015)
J/ApJ/659/1040 : VLBI monitoring of NGC 4258 (Argon+, 2007)
J/ApJ/652/1133 : BVI photometry of NGC 4258 Cepheids (Macri+, 2006)
J/A+A/268/419 : HII Regions in NGC 4258 (Courtes+ 1993)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
11- 18 F8.5 deg DEdeg Declination in decimal degrees (J2000)
20- 25 F6.3 mag gmag [15/25] SDSS g magnitude
27- 32 F6.3 mag rmag [14.5/24.5] SDSS r magnitude
34- 39 F6.3 mag imag [14/24.5] SDSS i magnitude
41- 43 I3 mmag e_gmag Uncertainty in gmag
45- 47 I3 mmag e_rmag Uncertainty in rmag
49- 51 I3 mmag e_imag Uncertainty in imag
53- 54 A2 --- Cal Used in calibration (SW or WG) (1)
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Note (1):
SW = used in SDSS-WIYN calibration;
WG = used in WIYN-Gemini calibration.
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Byte-by-byte Description of file: table[67].dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Star Variable identifier (G1)
6- 14 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
16- 23 F8.5 deg DEdeg Declination in decimal degrees (J2000)
25- 31 F7.3 d Per [6.975/157] Period
33- 38 F6.3 mag [21.5/26.1] Mean magnitude in SDSS r band
40- 45 F6.3 mag [21.42/25.7] Mean magnitude in SDSS i band
47- 52 F6.3 mag [22.1/26.9]? Mean magnitude in SDSS g band
54- 55 I2 mmag e_ [1/45] Uncertainty in (G2)
57- 58 I2 mmag e_ [1/65] Uncertainty in (G2)
60- 61 I2 mmag e_ [1/83]? Uncertainty in (G2)
63- 65 I3 mmag rAmp [105/813] Light curve amplitude in SDSS r band
67- 69 I3 mmag iAmp [100/625] Light curve amplitude in SDSS i band
71- 74 I4 mmag gAmp [112/1059]? Light curve amplitude in SDSS g band
76 A1 --- QA [ABC] Quality flag on variability based on
amplitude ratio (1)
78 A1 --- QR [ABC] Quality flag on variability based on
Period-Luminosity (P-L) residual (1)
80 A1 --- --- [F]
81- 82 I2 --- F14 [4/64]? Cross-identification with Fausnaugh et
al. (2014; 1303.5076)
84 A1 --- --- [M]
85- 92 A8 --- M06 Cross-identification with Macri et al. 2006
(J/ApJ/652/1133 <[MSB2006] A-NNNNNN> in Simbad)
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Note (1): See steps (c) and (d) in Section 5 of the paper.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Star Variable identifier (G1)
6- 14 F9.4 d MJD Modified Julian Date (JD-2400000.5)
16 A1 --- Band [gri] Bandpass used in observation
(SDSS g, r, or i)
18- 23 F6.3 mag mag [21.1/27.5] Magnitude in Band
25- 27 I3 mmag e_mag Uncertainty in mag (G2)
29- 31 I3 10-3 Phase [0/999] Phase (*103)
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Global Notes:
Note (G1): C###=Cepheid, V###=additional Variable (probably blend, highly
reddened Cepheid or Population II pulsator).
Note (G2): The uncertainties in mean magnitude reflect only the statistical
component; please refer to Table 2 in the paper for systematic
uncertainties.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 18-Jun-2015