The peculiar motions of early-type galaxies in two distant regions - III. The photometric data
We present R-band CCD photometry for 776 galaxies observed in the EFAR project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1 per cent and a precision of 0.03 mag per zero-point have been achieved. We give the circularly averaged surface b...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
1997
|
| _version_ | 1797073384842985472 |
|---|---|
| author | Saglia, R Burstein, D Baggley, G Bertschinger, E Colless, M Davies, R McMahan, R Wegner, G |
| author_facet | Saglia, R Burstein, D Baggley, G Bertschinger, E Colless, M Davies, R McMahan, R Wegner, G |
| author_sort | Saglia, R |
| collection | OXFORD |
| description | We present R-band CCD photometry for 776 galaxies observed in the EFAR project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1 per cent and a precision of 0.03 mag per zero-point have been achieved. We give the circularly averaged surface brightness profiles and the photometric parameters of the 762 programme galaxies, D n diameters (at 20.5 mag arcsec -2), half-luminosity radii R e, total magnitudes m T and average effective surface brightnesses 〈SB e〉. The photometric parameters are derived using the seeing-convolved, R 1/4-plus-exponential fitting algorithm described in Paper IV which optimally combines multiple profiles and corrects for sky subtraction errors. The parameters of the two-component fits are also given. We find that the diameters D n span the range 4.8-90 arcsec, with 〈logD n〉 = 1.30 or 20 arcsec. The run of the effective radii R e is 1.6-71.2 arcsec, with 〈log R e〉 = 0.84 or 6.9 arcsec. The total magnitudes m T extend from 10.57 to 15.97 mag, with a mean of 13.85 mag. The effective surface brightnesses 〈SB e〉 span the range 17.78-22.35 mag arcsec -2 with a mean of 19.89 mag arcsec -2. The mean photometric precisions of D n diameters, magnitudes and surface brightnesses are 0.9 per cent, 0.017 mag and 0.017 mag arcsec -2 respectively. In addition, the fitting scheme quantifies and minimizes the many systematic biases affecting the determination of galaxy photometric parameters. We find simple R 1/4 fits for only 14 per cent of the total, and simple exponential fits for ≉ 1 per cent of the total. The spread in sky values measured from the different profiles of the same object is less than 1 per cent in 85 per cent of the cases. In 80 per cent of the fits a reduced χ 2 of less than 12 is obtained. More than 90 per cent of the galaxies have at least one profile extending to more than 4 half-luminosity radii. More than 90 per cent of the galaxies are well resolved, having at least one profile where R e > 2Γ, where Γ is the FWHM of the point-spread function. More than 80 per cent of the profiles have a global signal-to-noise ratio larger than 300. The extrapolation needed to derive total magnitudes is less than 10 per cent for 80 per cent of the fits. More than 80 per cent of the galaxies have mean effective surface brightness larger than the observed sky brightness. In 90 per cent of the profiles the estimate of the contamination of the sky by the galaxy light is less than 1 per cent. Summarizing, the extensive internal comparisons, together with Monte Carlo simulations (see Paper IV), show that we derive total magnitudes and half-luminosity radii to better than 0.15 mag and 25 per cent respectively for 90 per cent of our sample. In contrast, external comparisons show that data in the literature can be strongly affected by systematic errors due to large extrapolations, small radial range, sky subtraction errors, seeing effects, and the use of a simple R 1/4 fit. The resulting errors can easily amount to more than 0.5 mag in the total magnitudes and 50 per cent in the half-luminosity radii. The errors on the combined quantity FP = log R e - 0.3 〈SB e〉 which enters the Fundamental Plane equation remain, however, always smaller than 0.03 dex. The galaxy type classification, based on all of the information available to us, shows that 31 per cent of the sample objects, visually selected from photographic images to be of early type, are in fact spiral or barred galaxies. The 69 per cent of galaxies classified as early-type can be subdivided into cD (8 per cent), E (12 per cent with a simple R 1/4 law best fit), and E/S0 (48 per cent with a disc-plus-bulge best fit). The photographic diameters D W measured in Paper I correlate with D n diameters or, equivalently, with the Fundamental Plane quantity FP = log R e - 0.3 〈SB e〉, with 23 per cent scatter for the early-type sample. © 1997 RAS. |
| first_indexed | 2024-03-06T23:21:20Z |
| format | Journal article |
| id | oxford-uuid:68d2fdd2-34ec-4444-800a-d774f73fc847 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:21:20Z |
| publishDate | 1997 |
| record_format | dspace |
| spelling | oxford-uuid:68d2fdd2-34ec-4444-800a-d774f73fc8472022-03-26T18:47:32ZThe peculiar motions of early-type galaxies in two distant regions - III. The photometric dataJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:68d2fdd2-34ec-4444-800a-d774f73fc847EnglishSymplectic Elements at Oxford1997Saglia, RBurstein, DBaggley, GBertschinger, EColless, MDavies, RMcMahan, RWegner, GWe present R-band CCD photometry for 776 galaxies observed in the EFAR project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1 per cent and a precision of 0.03 mag per zero-point have been achieved. We give the circularly averaged surface brightness profiles and the photometric parameters of the 762 programme galaxies, D n diameters (at 20.5 mag arcsec -2), half-luminosity radii R e, total magnitudes m T and average effective surface brightnesses 〈SB e〉. The photometric parameters are derived using the seeing-convolved, R 1/4-plus-exponential fitting algorithm described in Paper IV which optimally combines multiple profiles and corrects for sky subtraction errors. The parameters of the two-component fits are also given. We find that the diameters D n span the range 4.8-90 arcsec, with 〈logD n〉 = 1.30 or 20 arcsec. The run of the effective radii R e is 1.6-71.2 arcsec, with 〈log R e〉 = 0.84 or 6.9 arcsec. The total magnitudes m T extend from 10.57 to 15.97 mag, with a mean of 13.85 mag. The effective surface brightnesses 〈SB e〉 span the range 17.78-22.35 mag arcsec -2 with a mean of 19.89 mag arcsec -2. The mean photometric precisions of D n diameters, magnitudes and surface brightnesses are 0.9 per cent, 0.017 mag and 0.017 mag arcsec -2 respectively. In addition, the fitting scheme quantifies and minimizes the many systematic biases affecting the determination of galaxy photometric parameters. We find simple R 1/4 fits for only 14 per cent of the total, and simple exponential fits for ≉ 1 per cent of the total. The spread in sky values measured from the different profiles of the same object is less than 1 per cent in 85 per cent of the cases. In 80 per cent of the fits a reduced χ 2 of less than 12 is obtained. More than 90 per cent of the galaxies have at least one profile extending to more than 4 half-luminosity radii. More than 90 per cent of the galaxies are well resolved, having at least one profile where R e > 2Γ, where Γ is the FWHM of the point-spread function. More than 80 per cent of the profiles have a global signal-to-noise ratio larger than 300. The extrapolation needed to derive total magnitudes is less than 10 per cent for 80 per cent of the fits. More than 80 per cent of the galaxies have mean effective surface brightness larger than the observed sky brightness. In 90 per cent of the profiles the estimate of the contamination of the sky by the galaxy light is less than 1 per cent. Summarizing, the extensive internal comparisons, together with Monte Carlo simulations (see Paper IV), show that we derive total magnitudes and half-luminosity radii to better than 0.15 mag and 25 per cent respectively for 90 per cent of our sample. In contrast, external comparisons show that data in the literature can be strongly affected by systematic errors due to large extrapolations, small radial range, sky subtraction errors, seeing effects, and the use of a simple R 1/4 fit. The resulting errors can easily amount to more than 0.5 mag in the total magnitudes and 50 per cent in the half-luminosity radii. The errors on the combined quantity FP = log R e - 0.3 〈SB e〉 which enters the Fundamental Plane equation remain, however, always smaller than 0.03 dex. The galaxy type classification, based on all of the information available to us, shows that 31 per cent of the sample objects, visually selected from photographic images to be of early type, are in fact spiral or barred galaxies. The 69 per cent of galaxies classified as early-type can be subdivided into cD (8 per cent), E (12 per cent with a simple R 1/4 law best fit), and E/S0 (48 per cent with a disc-plus-bulge best fit). The photographic diameters D W measured in Paper I correlate with D n diameters or, equivalently, with the Fundamental Plane quantity FP = log R e - 0.3 〈SB e〉, with 23 per cent scatter for the early-type sample. © 1997 RAS. |
| spellingShingle | Saglia, R Burstein, D Baggley, G Bertschinger, E Colless, M Davies, R McMahan, R Wegner, G The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title | The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title_full | The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title_fullStr | The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title_full_unstemmed | The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title_short | The peculiar motions of early-type galaxies in two distant regions - III. The photometric data |
| title_sort | peculiar motions of early type galaxies in two distant regions iii the photometric data |
| work_keys_str_mv | AT sagliar thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT bursteind thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT baggleyg thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT bertschingere thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT collessm thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT daviesr thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT mcmahanr thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT wegnerg thepeculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT sagliar peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT bursteind peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT baggleyg peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT bertschingere peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT collessm peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT daviesr peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT mcmahanr peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata AT wegnerg peculiarmotionsofearlytypegalaxiesintwodistantregionsiiithephotometricdata |