Star-forming galaxies in low-redshift clusters: Data and integrated galaxy properties

Star-forming galaxies in low-redshift clusters: Data and integrated galaxy properties

Key Words.:
galaxies: clusters: general – galaxies: evolution – galaxies: interactions
1

Abstract

Context:

Aims:This paper is a continuation of an ongoing study of the evolutionary processes affecting cluster galaxies.

Methods:Both CCD R band and H narrow-band imaging was used to determine photometric parameters (, , H flux, and equivalent width) and derive star formation rates for 227 CGCG galaxies in 8 low-redshift clusters. The galaxy sample is a subset of CGCG galaxies in an objective prism survey (OPS) of cluster galaxies for H emission.

Results:It is found that detection of emission-line galaxies in the OPS is 85%, 70%, and 50% complete at the mean surface brightness values of , , and W m arcsec, respectively, measured within the R band isophote of 24 mag for the galaxy.

Conclusions:The CCD data, together with matched data from a recent H galaxy survey of UGC galaxies within km , will be used for a comparative study of R band and H surface photometry between cluster and field spirals.

1 Introduction

While the transformation of cluster disc galaxies from predominantly spiral to mainly lenticular galaxies over the past 5 Gyr is well established (e.g. Butcher & Oemler 1978, 1984; Dressler et al. 1997; Fasano et al. 2000), the mechanism or mechanisms that have affected this transformation are not so clear. However, a comparative study of the rate, distribution, and morphological dependence of star formation between cluster and field spirals appears to be a promising enquiry that can help to disentangle some of the suggested transformation processes. For example, ram-pressure stripping of the cold interstellar gas of spirals by the hot ionised intracluster medium (e.g. Gunn & Gott 1972; Quilis, Moore & Bower 2000) should be most effective in the centres of rich clusters, and may lead to a rapid truncation of the star forming disc, but provides no obvious mechanism to promote circumnuclear star formation. On the other hand, strangulation, i.e. the stripping of an hypothesised hot halo gas of spirals (e.g. Larson et al. 1980; Bower & Balogh 2004) should be a more gradual process; simulations by Bekki et al. (2002) have shown that this would lead to anemic spirals rather than truncation. Tidal interactions with the cluster potential can induce star formation across both bulge and disc (e.g. Byrd & Valtonen 1990), whereas low-velocity interactions between galaxies can be efficient at triggering star formation in central regions (e.g. Kennicutt et al. 1987; Mihos et al. 1992; Iono et al. 2004). In contrast, galaxy harassment, i.e. frequent galaxy high-speed encounters within a cluster, are expected to trigger modest disc-wide response of star formation for giant spirals (see Moore et al. 1999; Mihos 2004).

Systematic comparative studies of the massive star formation properties of cluster and field galaxies have already produced interesting results. Moss & Whittle (2000, 2005) undertook an objective prism survey (OPS) of a complete magnitude-limited sample of 727 CGCG galaxies (Zwicky et al. 1960–68) in 8 low-redshift clusters. These authors show an enhancement of circumnuclear starburst emission in cluster spirals associated with a disturbed morphology that is attributed to slow galaxy–galaxy encounters and major and minor mergers (see also Moss 2006). Koopmann & Kenney (2004a,b) have pioneered a comparative study of the massive star formation properties of Virgo cluster and isolated bright () S0–Scd galaxies via analyses of R and H surface photometry. They show that the median total normalised massive star formation rate is reduced by a factor of 2.5 for cluster galaxies as compared to the field. Few of the cluster or isolated galaxies are anemic, suggesting that strangulation is not a major contributory factor in the reduced star formation rates of Virgo spirals; rather, this reduction is caused by spatial truncation of the star forming discs. In addition, several of the truncated galaxies show evidence of recent tidal interaction or minor mergers, such as enhanced central star formation rates and disturbed stellar discs.

It is intended to extend the analyses of Koopmann & Kenney to the clusters studied by Moss & Whittle using R band and narrow-band H imaging obtained for a 227 subset of CGCG galaxies of mainly types Sa + later in the OPS. Clusters in the OPS include those of greater central galaxy density (most especially Abell 1367 and the Coma cluster) where on-going environmental effects on galaxy morphology and transformation may be expected to be even more pronounced than for the Virgo cluster. In the present paper, we discuss observational data and data reduction for imaging data, and present global photometric properties and derived star formation rates. Completeness limits for the OPS are also determined. A second paper (Bretherton et al., in preparation) will give results of a comparative study of R band and H surface photometry between the sample of 227 CGCG cluster galaxies, and sets of galaxies, matched according to morphology and absolute magnitude to the cluster sample, taken from the recent H galaxy survey of UGC galaxies within km (HGS, Shane 2002; James et al. 2004).

In the present paper, sample selection and observations of the cluster data are discussed in section 2. The data reduction procedures and photometry are outlined, and global parameters derived for all sample galaxies, in sections 3 and 4 respectively. Section 5 uses a complete sample of Sa–Sc galaxies within the cluster data to investigate the completeness of the objective prism survey (OPS, see Moss & Whittle 2000, 2005) on which present sample selection is based. Conclusions of this paper are given in section 6.

2 Sample selection and observations

2.1 Selection of cluster sample

The galaxy samples chosen for the present study are sub-samples of low-redshift cluster galaxies previously surveyed by Moss & Whittle (2000; 2005). These authors undertook an extensive objective prism survey of combined H + [NII] emission for CGCG galaxies (Zwicky et al. 1960–68) in 8 low-redshift Abell clusters (viz. Abell 262, 347, 400, 426, 569, 779, 1367, and 1656). This objective prism survey (hereafter, OPS) comprised a total of 727 CGCG galaxies, including double galaxy components (), and is essentially complete within Abell radii of the cluster centres. (The Abell radius, = 2.00 Mpc, assuming a Hubble constant, km , see Abell 1958). For convenience, Table 1 summarises basic data for the clusters surveyed, adapted from Moss & Whittle (2000) and Moss (2006).

Cluster Cluster centre
R.A. (1950) Dec. (arcmin) (Mpc) () (km )
Abell 262 1 499 35 54 13659 -2509 105 1.83 0.86 0.0167 537 38
Abell 347 2 22.7 41 39 141.17 -17.63 91 1.87 0.87 0.0192 550 14
Abell 400 2 55.0 5 50 170.25 -44.93 72 1.32 0.62 0.0227 392 10
Abell 426 3 15.3 41 20 150.39 -13.38 96 3.67 1.72 0.0177 1076 55
Abell 569 7 5.4 48 42 168.58 22.81 88 1.42 0.66 0.0198 417 26
Abell 779 9 16.8 33 59 191.07 44.41 75 0.98 0.46 0.0232 290 11
Abell 1367 11 41.9 20 7 234.81 73.03 80 2.58 1.21 0.0216 762 62
Abell 1656 12 57.4 28 15 58.09 87.96 74 3.01 1.41 0.0232 890 131

E–S0/a galaxies only

Cluster centres are taken from Abell, Corwin & Olowin (1989). The Abell radius (Abell 1958), , corresponds to Mpc. Values for the virial radius, , are from Moss (2006), where is assumed. Cluster mean redshifts, , and velocity dispersions, , are based on redshifts of galaxies of types E–S0/a only. These objects are more likely to be in dynamic equilibrium with the cluster potential and follow a Gaussian distribution, as expected for virially relaxed galaxies within the cluster (see Moss 2006). The mean redshift has been corrected to the centroid of the Local Group following RC2 (de Vaucouleurs, de Vaucouleurs & Corwin 1976).

Table 1: Surveyed clusters

The sub-samples of the OPS were restricted to galaxies with velocities within of the cluster mean, and excluded known AGNs since the present study is mainly concerned with star formation properties. Two principal sub-samples were chosen: (a) galaxies of types Sa–Sc; this sample is complete for six clusters (viz. all clusters of the OPS except Abell 262 and 347), and (b) emission-line galaxies (ELGs) of the OPS of types S0/a and later (including ‘peculiar’ galaxies whose types are outside the Hubble sequence, see Moss & Whittle 2000).

2.2 Observations

The observations of the cluster sample were taken on the 1.0m Jacobus Kapteyn Telescope (JKT) and the 2.6m Nordic Optical Telescope (NOT) both situated on the island of La Palma. The JKT data consist of 2 weeks of observations taken in 1994 and 1998, some data taken in 1997, and a handful of galaxies observed in earlier service time, although the majority of the service galaxies were also observed in subsequent runs. Altogether, the JKT runs provided H and R band data for 143 sample galaxies, with repeat measurements for 14 of these. A 3 night observing run using ALFOSC (Andalucia Faint Object Spectrograph and Camera) on the NOT in January 2005 provided data for a further 87 galaxies, plus repeat measurements for eight JKT galaxies and two NOT galaxies.

The galaxies in the cluster sample have recession velocities in the range km . Therefore, in order to cover the redshifted H emission in all objects, it was necessary to use a series of narrowband filters. These have a typical passband width of 40–55 Å, with peak wavelengths ranging from 6626–6788 Å. Their transmission profiles for the JKT and NOT observations are shown in Figures 1a and 1b respectively.

Figure 1: Transmission profiles for both JKT and NOT redshifted narrowband H filters. Filter H669 in the JKT plot was used only for service data.

The majority of the JKT observations made use of pixel TEK4 CCD camera, with field of view arcmin; for the few galaxies surveyed in the early service observations, a pixel EEV7 CCD camera was used, with field of view arcmin. R band continuum observations were taken using a Harris R band filter, with central wavelength of 6373 Å and passband width of 1491 Å.

The more recent NOT observations utilised the standard ALFOSC CCD8 pixel back-illuminated device with a field of view approximately arcmin. R band continuum observations were taken using a Bessell R filter with central wavelength of 6500 Å and passband width of 1300 Å. The broad R band filter is used for continuum subtraction, rather than off-band H filters, due to the much shorter exposure times required. James et al. (2004) found that scaled R band exposures gave excellent continuum subtraction when taken in dark sky conditions. The R band data are also used to trace the older, underlying stellar population of the sample galaxies in subsequent analysis.

As well as the galaxy images, a number of calibration frames were also taken. These included bias frames taken at the start and end of each night, sky flats (at least three observations of blank areas of sky, in each filter used, taken at twilight every night), and photometric standards observed throughout the night in the R band filter to monitor photometric conditions and calibrate the galaxy data. Spectrophotometric standards were also observed nightly through each filter.

2.3 The final observed cluster sample

Combining data from all runs, a total of 230 CGCG galaxies were observed. These galaxies are listed in Table 2, where the first three columns of the table give the CGCG number of the galaxy, the observing run, and narrow-band filter used to obtain the H data respectively.

The observed galaxies include all Sa–Sc galaxies in six Abell clusters (A400, 426, 569, 779, 1367, 1656) and emission-line galaxies of types S0/a and later in the 8 clusters of the OPS. Selection criteria for the galaxies (see section 2.1 above) are a velocity within of the cluster mean, a magnitude, , a radial distance from the cluster centre, , and that the galaxies are not known AGNs. Some 18 galaxies are listed in Table 2 that do not strictly meet these selection criteria: 13 galaxies have velocities greater than from the cluster mean (viz. CGCG 415-028, 415-031, 415-033, 415-035, 415-051, 415-58, 540-058, 540-071, 181-017, 181-023, 126-075, 127-002, and 127-012B) and 5 galaxies are fainter than (viz. CGCG 540-112B, 234-088B, 127-025B, 97-092A and 127-051B). These were observed in the preliminary phase of the project and have been included for completeness, but are not included in any of the statistical analyses in the present or subsequent papers. Twenty-four more galaxies (mainly in Abell 1367) lie beyond 1.5 Abell radii from the cluster centre.

3 Data reduction

3.1 Continuum subtraction

Standard IRAF and Starlink tasks were used to debias, flat-field and remove cosmic ray defects from all images, as well as to align pairs of R band and H images. Some galaxies in the cluster sample had uneven sky backgrounds after processing. For the NOT data this was simply a gradient across the H images. The JKT data were more variable, with some images having smooth, even backgrounds, whilst others showed gradients, marks or rings. Background variability was reduced by fitting a surface to the sky in affected images. All stars and galaxies in a frame were identified and masked out, and a polynomial fit was made to the remaining background using the Starlink KAPPA command surfit. This was subtracted from the original image, removing much of the variability and typically reducing sky background errors in affected frames by a factor of 15.

A critical stage in the data reduction process is the scaling and subtraction of the continuum contribution from the narrowband H images. Scaling factors were calculated from a comparison of 9 field stars in each galaxy image pair and from standard star observations. A mean scaling factor was then found for each filter pair across the full dataset. Scaling factors were consistent for all objects observed in the same H filter during photometric conditions.

The scaled continuum images were subtracted from the H images to leave continuum-free H emission. This latter includes a contribution from the neighbouring [NII] lines ( 6548, 6585Å) that lie within the filter bandpass.

3.2 Calibration

Images were calibrated by using R band standard star observations to determine extinction corrections and zeropoints for each night. Six galaxies (viz. CGCG 415-033, 522-011, 522-021, 522-053, 522-072, and 539-031) were observed in non-photometric conditions on the second night of the NOT run. For these galaxies separate R band calibration exposures were taken under photometric conditions on the following night and used to calibrate the non-photometric data.

Calibrated images were normalised to 1 count = 25 mag. The apparent magnitude of each galaxy in a given filter, , is then simply given by,

where is the number of sky-subtracted counts measured directly from the R band or continuum subtracted H images, and is a correction for Galactic extinction. Values of were based on the Galactic extinction maps of Schlegel et al. (1998) converted to R band extinction using the methods of Cardelli et al. (1989).

For narrow-band images, the measured magnitude, , of a galaxy can be considered as an equivalent magnitude in the R band. Following the calibration of R(Cousins) from Bessell (1979), corresponds to a flux density of  W  ; this relation was used to determine H flux values. Finally these flux values were corrected both for the centering of the H emission in the narrow-band filter, and for slight over-subtraction of the continuum due to the wavelength overlap of the R and narrow-band filters, to obtain final H flux values used for the subsequent analysis. Values of the H equivalent width (EW) for individual galaxies were obtained by dividing the H flux by the corresponding R band flux density.

3.3 Photometry

Photometry of individual galaxies was performed using a series of apertures of increasing radius/semi-major axis for each galaxy. Typically between 25 and 60 apertures were used to cover the full galaxy and measure out into the sky background. Elliptical apertures were generally used with major to minor axis ratio taken from NED or from Moss & Whittle (unpublished), and with position angles determined from the images themselves using the Starlink function Object Detection in GAIA. For some objects with no published axis ratio values, or for which the given axis ratio did not appear to fit well the outer isophotes of the galaxy, axis ratios were estimated from the data. For face-on galaxies, or those with peculiar shapes, circular apertures were employed.

The centre of each galaxy was generally found by centroiding on the nucleus of the R band image in GAIA. In a few cases it was found necessary to determine the centre by eye. The R band was preferred for the centroiding process due to the relative smoothness of the R band emission compared to the clumpier H data.

Before photometry was carried out, all stars or stellar residuals were masked from each image. Counts were then measured in each aperture, with sky subtraction performed using an annular sky region outside the largest galaxy aperture. These were converted to H flux or R band flux density according to the procedure given in section 3.2, and were then combined to create growth curves for R band flux density, H flux and EW (H flux/R flux density), which form the basis of the remainder of this study.

4 Global parameters

Global parameters for the observed galaxies are listed in Table 2. These parameters include the absolute B magnitude; the isophotal radius, , which is the semi-major axis of the isophote equal to 24 mag ; the apparent magnitude, , which corresponds to the light enclosed within this isophote; values of H flux and EW; and the total star formation rate for the galaxy. Each of these parameters is explained in more detail the sections that follow.

CGCG Run H Type R.A. (2000) Dec. a/b PA H flux H EW SFR
filter (h    m    s) (°   ′   ″) () (″) () (nm) (Myr)
Abell 262
521-073 JKT94 H668 -20.9 S pec 01 44 35.5 +37 41 45 1.6 17 31 13.17 58(5) 4.6(0.4) 4.8
521-074 JKT94 H668 -19.8 S: pec 01 44 38.4 +34 39 37 4.5 86 20 14.70 12(1) 3.9(0.4) 1.0
521-078 JKT94 H668 -19.6 Sc/SBc 01 45 51.8 +35 06 39 1.4 144 18 14.27 19(2) 4.2(0.4) 1.6
522-003 JKT94 H666 -19.3 pec 01 46 56.8 +34 46 21 1.5 87 17 13.97 16(2) 2.7(0.3) 1.4
522-006 JKT94 H668 -19.3 SAbc: pec 01 47 43.6 +35 01 21 1.0 17 13.91 17(2) 2.6(0.3) 1.4
522-011 NOT H50 -19.0 S0/a 01 49 18.1 +34 58 06 1.7 40 16 14.70 15(1) 5.1(0.4) 1.2
522-020 JKT94 H666 -21.6 SBb 01 50 44.2 +35 17 04 1.7 141 68 12.32 45(7) 1.6(0.3) 3.8
522-021 NOT H50 -20.5 S 01 50 47.9 +35 55 58 3.8 60 72 12.92 3(3) 0.2(0.2) 0.2
522-024 JKT94 H668 -20.3 SA: pec 01 50 47.9 +35 55 58 1.5 163 34 13.16 36(4) 2.9(0.3) 3.0
522-025 JKT94 H671 -19.2 SAbc: 01 52 02.8 +36 07 52 1.4 6 19 14.04 20(2) 3.5(0.3) 1.7
522-038 NOT H51 -20.7 Sc/SBc 01 52 45.9 +36 37 10 1.0 37 12.72 45(5) 2.5(0.3) 3.7
522-041 NOT H51 -20.3 SABc 01 52 53.9 +36 03 10 1.0 32 13.25 59(4) 5.3(0.4) 4.9
522-053 NOT H51 -19.5 S0: 01 53 57.0 +36 38 28 2.3 35 28 13.97 5(1) 0.9(0.2) 0.4
522-055 JKT94 H668 -20.6 SBc 01 54 19.8 +36 37 47 4.2 138 36 13.10 8(3) 0.6(0.2) 0.6
522-058 JKT92 H669 -20.5 SBa 01 54 53.8 +36 55 05 1.2 73 38 13.05 20(4) 1.4(0.3) 1.7
522-069 JKT94 H668 -19.7 SAc: 01 55 58.5 +37 07 46 1.1 36 20 13.31 14(3) 1.2(0.3) 1.1
522-072 NOT H50 -19.2 E/S0:: pec 01 56 21.4 +35 34 21 1.2 126 15 14.22 7(1) 1.5(0.3) 0.6
522-074 JKT94 H668 -19.9 Sc 01 56 21.1 +37 27 08 8.7 123 24 15.78 2(1) 2.1(0.9) 0.2
522-077 JKT94 H668 -19.1 SBb: pec 01 56 30.5 +37 20 08 1.2 43 15 14.02 8(2) 1.4(0.3) 0.7
522-079 JKT94 H668 -19.4 SA:c: 01 56 39.9 +35 35 32 1.8 135 17 14.12 13(2) 2.4(0.3) 1.1
522-081 JKT92 H669 -20.3 S 01 56 46.1 +36 53 11 2.0 54 46 13.64
522-086 JKT94 H668 -22.2 SAB:c 01 57 42.2 +35 54 58 1.5 126 71 11.59 181(18) 3.4(0.3) 15.1
522-096 JKT94 H668 -20.3 Sc 01 59 06.7 +36 03 47 8.0 107 31 14.95 4(1) 1.4(0.3) 0.3
522-100 JKT94 H666 -19.7 SB(s)dm 02 00 11.2 +37 36 12 1.2 6 30 13.99 15(2) 2.5(0.3) 1.2
522-102 JKT94 H666 -21.1 SB:ab 02 00 54.9 +38 12 39 2.6 83 60 13.00 31(4) 2.1(0.3) 2.6
Abell 347
538-037 JKT94 H668 -20.2 Sc 02 15 54.1 +42 49 26 4.0 105 29 15.47 4(1) 2.6(0.7) 0.4
538-043 JKT92 H669 -20.1 pec 02 20 03.8 +41 16 28 1.5 120 33 14.00 42(3) 7.2(0.5) 4.7
538-046 JKT94 H668 -19.7 SA:b: 02 20 35.0 +41 34 27 1.2 64 22 14.17 8(4) 1.6(0.7) 0.9
538-048 JKT92 H669 -20.5 S pec 02 21 23.3 +42 52 35 3.6 126 51 13.95 18(2) 2.9(0.3) 2.0
523-028 JKT98 H671 -21.5 SA(s)b pec 02 21 28.7 +39 22 32 1.6 51 65 12.28
523-029 JKT98 H671 -20.2 SB(s)a pec 02 21 32.6 +39 21 25 3.8 89 46 14.43 9(3) 2.2(0.7) 1.0
538-054 JKT94 H671 -19.5 Sa: 02 22 50.4 +42 09 29 2.0 93 22 14.75 5(1) 1.6(0.3) 0.5
538-063 JKT94 H668 -19.8 Sbc 02 24 47.3 +42 01 28 2.7 48 26 14.37 8(1) 1.8(0.3) 0.9
539-023 JKT94 H668 -20.7 SAc 02 26 05.2 +42 08 39 1.4 63 18 13.14 1(3) 0.1(0.2) 0.1
539-024 JKT92 H669 -20.5 SBb 02 26 46.3 +41 50 04 2.0 142 50 13.24 35(4) 3.0(0.3) 4.0
539-025 JKT94 H666 -19.8 SB pec 02 26 53.1 +41 41 25 1.2 11 28 13.48 13(2) 1.4(0.3) 1.4
539-029 JKT94 H671 -19.7 S 02 27 31.2 +41 55 51 2.0 47 30 13.69 14(2) 1.7(0.3) 1.5
539-030 NOT H51 -20.8 Sb: 02 27 34.6 +41 58 39 1.6 105 35 13.06 52(5) 3.9(0.4) 5.8
539-031 NOT H51 -19.9 S0/a 02 27 36.7 +42 00 28 1.3 142 20 13.99 25(2) 4.4(0.4) 2.8
539-036 JKT92 H669 -20.8 Sab 02 31 14.3 +40 23 25 3.3 117 51 13.87 15(2) 2.2(0.3) 1.6
539-038 JKT92 H669 -19.3 S pec 02 31 26.6 +40 14 51 1.0 23 14.24 14(2) 3.0(0.3) 1.6
539-044 JKT94 H668 -20.1 pec 02 33 40.2 +41 20 47 3.0 143 28 14.17 21(2) 4.2(0.4) 2.4
Abell 400
415-020 NOT H53 -21.3 S0 02 53 41.2 +06 15 55 3.8 142 80 12.55 30(6) 1.4(0.3) 5.3
415-021 JKT94 H674 -20.9 SAB:c 02 53 58.8 +05 59 16 1.1 7 29 13.83 33(3) 4.8(0.4) 5.8
415-025 JKT94 H674 -20.5 S 02 55 19.9 +06 07 29 1.0 0 20 13.80 33(3) 4.6(0.4) 5.8
415-028 NOT H53 -21.1 SABc 02 55 46.9 +06 13 03 1.0 36 13.24 27(3) 2.4(0.3) 4.8
415-030 JKT94 H674 -21.5 Sc 02 55 57.6 +06 29 41 2.5 165 43 13.70 26(3) 3.3(0.3) 4.6
415-031 NOT H53 -21.0 Sc 02 56 17.6 +04 31 46 3.5 158 44 14.67 8(1) 2.5(0.3) 1.3
415-032 NOT H53 -21.0 SBbc 02 56 22.7 +06 09 19 2.5 6 32 14.63 11(1) 3.6(0.3) 2.0
415-033 NOT H53 -20.5 S0:: pec 02 56 28.3 +04 36 38 1.0 19 14.02 16(2) 2.9(0.3) 2.8
415-035 NOT H53 -21.4 SBa 02 56 43.1 +07 20 01 1.0 39 12.61 16(5) 0.8(0.2) 2.9
415-037 NOT H53 -21.3 Sc 02 56 46.9 +04 58 40 3.7 141 48 13.71 8(2) 1.2(0.3) 1.5
415-038 NOT H51 -20.5 S0 02 56 56.6 +06 12 20 1.3 40 19 14.20 13(1) 2.9(0.3) 2.4
415-039 NOT H53 -21.0 SA:b 02 57 09.2 +05 19 15 1.5 67 32 13.48 10(2) 1.1(0.3) 1.8
415-048 JKT94 H671 -21.2 S 02 58 29.7 +06 18 23 1.7 47 34 13.18 36(4) 2.9(0.3) 6.4
415-051 NOT H53 -21.0 Sab 02 59 52.3 +06 31 59 1.8 156 32 13.68 15(2) 2.0(0.3) 2.7
415-052 NOT H51 -20.4 SA0/a: 03 00 08.6 +05 48 16 1.0 23 13.70 1(2) 0.1(0.2) 0.1
415-058 NOT H53 -20.6 Sbc: 03 04 39.2 +05 26 35 1.8 57 29 14.20 8(1) 1.7(0.3) 1.4
Table 2: Global parameters for 227 CGCG galaxies in eight low redshift Abell clusters
CGCG Run H Type R.A. (2000) Dec. a/b PA H flux H EW SFR
filter (h    m    s) (°   ′   ″) () (″) () (nm) (Myr)
Abell 426
540-047 NOT H51 -21.1 Sb 03 09 42.7 +40 58 27 5.5 130 54 13.29
540-049 JKT94 H662 -21.3 S-Irr 03 10 12.9 +40 45 56 2.0 71 29 12.54 50(7) 2.2(0.3) 5.0
540-058 NOT H53 -20.3 Sb pec 03 13 10.2 +42 59 49 1.7 25 22 14.18 13(1) 2.8(0.3) 1.3
525-009 JKT94 H666 -21.0 SBc 03 14 40.5 +39 37 03 1.4 139 25 12.93 55(5) 3.5(0.3) 5.5
525-011 NOT H50 -20.9 Sb 03 14 58.0 +39 20 56 2.2 37 40 13.61 21(2) 2.6(0.3) 2.1
540-064 JKT92 H669 -21.7 SBb 03 15 01.4 +42 02 09 1.1 70 50 12.54 88(18) 3.9(0.8) 8.8
540-067 JKT94 H668 -20.1 SA:a: 03 15 20.5 +41 36 45 1.3 37 18 14.11 17(2) 3.2(0.3) 1.7
540-069 JKT94 H666 -21.7 SABc 03 16 00.8 +40 53 08 2.8 3 41 13.90 10(7) 1.5(1.1) 1.0
540-070 JKT94 H668 -21.1 Sab 03 16 01.0 +42 04 28 2.4 165 46 13.15 5(4) 0.4(0.2) 0.5
540-071 NOT H53 -20.3 SA:a: 03 16 02.9 +42 55 18 1.4 77 27 13.95 16(2) 2.7(0.3) 1.6
540-073 NOT H50 -21.6 Sa 03 16 26.1 +41 31 50 5.7 67 82 12.95 2(3) 0.1(0.2) 0.2
540-078 NOT H51 -20.7 Sa: 03 16 59.7 +41 21 24 4.7 71 54 13.38 2(2) 0.2(0.2) 0.2
540-083 NOT H50 -21.0 Sab 03 17 50.4 +41 58 03 5.0 89 70 13.67 1(2) 0.1(0.2) 0.1
540-084 JKT92 H669 -21.5 SBb 03 17 52.3 +43 18 15 1.8 68 57 12.70 35(16) 1.8(0.8) 3.5
540-091 JKT92 H669 -22.0 SBc 03 18 45.3 +43 14 27 2.2 0 54 13.66 52(4) 6.5(0.5) 5.2
540-093 NOT H50 -21.3 SAb 03 18 45.2 +41 29 19 1.7 130 39 13.11
540-094 JKT94 H671 -20.9 Sbc 03 18 53.4 +40 35 45 2.4 62 27 13.45 20(3) 2.1(0.3) 2.0
540-100 JKT94 H674 -20.7 Sc? pec 03 19 27.4 +41 38 07 2.5 119 37 13.58 12(2) 1.4(0.3) 1.2
540-103 JKT94 H668 -22.9 pec: 03 19 48.2 +41 30 42 1.3 104 ** 10.44 658(57) 4.2(0.4) 66.0
540-106 NOT H50 -20.3 Sa? 03 20 05.2 +40 54 22 3.0 178 38 13.81
540-112A NOT H50 -20.6 … pec 03 21 19.9 +41 55 55 1.0 40 12.92 17(4) 1.1(0.3) 1.7
540-112B NOT H50 -20.7 S:… pec 03 21 20.0 +41 55 44 5.0 112 59 13.84 3(2) 0.5(0.2) 0.3
540-114 NOT H50 -20.6 S:a: 03 21 32.8 +40 24 37 3.5 14 47 13.75 1(2) 0.2(0.2) 0.1
540-121 JKT92 H669 -21.4 SB:b 03 22 53.8 +42 33 12 3.8 129 77 12.76 19(9) 1.0(0.5) 1.9
541-005 NOT H50 -21.6 Sb 03 25 52.3 +40 44 56 4.7 128 67 13.26 18(3) 1.6(0.3) 1.8
541-006 NOT H51 -20.7 SBb 03 25 59.2 +40 47 21 1.0 43 12.45 29(6) 1.2(0.3) 2.9
541-008 NOT H51 -22.0 Sab 03 26 27.6 +40 30 29 5.0 68 88 12.73 6(4) 0.3(0.2) 0.6
541-009 JKT94 H666 -20.5 SBc 03 27 39.8 +40 53 49 1.3 114 30 13.55 11(2) 1.3(0.3) 1.1
541-011 NOT H50 -21.2 SB:b: pec 03 28 27.8 +40 09 16 2.7 76 44 13.26 74(5) 6.8(0.5) 7.5
541-017 JKT94 H666 -21.6 pec: 03 30 01.8 +41 49 55 2.1 118 45 12.45 117(9) 4.8(0.4) 11.7
Abell 569
234-043 JKT94 H668 -21.1 SB:ab 07 03 02.8 +49 25 28 2.3 43 40 13.21 22(3) 1.8(0.3) 2.6
234-050 NOT H51 -20.8 SBa: 07 06 00.3 +50 30 37 2.8 131 48 12.76 3(4) 0.2(0.2) 0.4
234-051 NOT H51 -20.5 SBa 07 05 59.0 +50 45 22 1.3 124 41 13.00 8(3) 0.6(0.2) 0.9
234-056 JKT97 H669 -20.1 S pec 07 07 32.4 +48 54 00 1.5 121 18 14.42 28(2) 7.0(0.5) 3.4
234-057 NOT H51 -19.1 pec 07 07 51.4 +48 24 55 1.0 13 15.01 6(1) 2.7(0.3) 0.7
234-060 NOT H51 -21.1 SBb 07 08 11.0 +50 40 55 1.1 99 65 11.88 29(10) 0.8(0.2) 3.5
234-061 JKT94 H671 -19.5 SAa: 07 08 09.7 +48 55 46 1.1 93 17 13.86 3(2) 0.5(0.2) 0.4
234-062 NOT H51 -20.1 SB:a: 07 08 12.2 +49 08 17 1.4 100 28 13.73 3(2) 0.4(0.2) 0.3
234-065 NOT H51 -19.3 SB: pec 07 08 31.2 +48 08 13 1.0 16 14.67 11(1) 3.5(0.3) 1.3
234-066 JKT97 H669 -20.0 pec: 07 08 34.2 +50 37 53 1.7 3 32 14.15 24(2) 4.6(0.4) 2.8
234-067 JKT94 H671 -20.0 Sa: 07 08 47.3 +48 59 41 1.4 71 23 14.28 17(2) 3.7(0.3) 2.0
234-069 JKT97 H669 -19.5 Sa: 07 09 03.6 +48 34 24 1.2 139 19 14.54 14(1) 3.8(0.4) 1.6
234-071 JKT94 H666 -19.7 SB: pec 07 09 15.9 +49 49 13 1.2 118 22 14.00 24(2) 4.1(0.4) 2.9
234-077 JKT94 H671 -19.9 S0: 07 09 39.4 +47 54 54 1.7 140 29 13.67
234-079A JKT94 H671 -19.8 S: pec 07 09 54.8 +47 54 28 1.6 120 22 14.44 14(1) 3.5(0.3) 1.7
234-079B JKT94 H671 -19.9 S: pec 07 09 53.6 +47 54 47 2.7 16 35 14.31 10(1) 2.3(0.3) 1.2
234-085 NOT H51 -19.3 07 10 52.2 +48 12 13 1.4 133 15 15.01 6(1) 2.7(0.3) 0.7
234-088A NOT H51 -20.4 Sab 07 11 01.2 +48 30 47 3.0 160 48 13.32 9(3) 0.8(0.2) 1.0
234-088B NOT H51 -18.8 07 11 00.8 +48 31 56 1.7 149 16 14.95 3(1) 1.4(0.3) 0.4
234-090 JKT94 H668 -20.5 Sbc 07 10 58.3 +49 01 22 4.0 103 33 14.83 5(1) 1.8(0.3) 0.6
234-092 NOT H51 -19.4 Sa: 07 11 08.8 +49 53 58 1.0 21 14.26 10(1) 2.2(0.3) 1.2
234-093 JKT94 H668 -20.8 SBb 07 11 28.0 +48 14 24 1.4 54 41 12.88 18(4) 1.1(0.3) 2.2
234-094 JKT97 H669 -19.8 S-Irr 07 11 30.3 +49 04 50 1.4 175 25 14.44 12(1) 3.1(0.3) 1.4
234-096 NOT H51 -19.8 E/S0 07 11 38.2 +46 56 09 1.0 18 13.96 7(1) 1.2(0.3) 0.8
234-102 NOT H51 -21.0 Sb: 07 12 51.0 +49 00 21 4.0 153 58 13.48 10(2) 1.1(0.3) 1.2
234-103 NOT H51 -19.9 Sa: 07 12 56.0 +49 45 53 1.2 152 26 13.69 6(2) 0.9(0.2) 0.8
234-107 JKT94 H668 -19.8 Sc 07 13 47.6 +50 15 26 2.0 56 21 14.10 14(2) 2.7(0.3) 1.7
234-114 NOT H51 -19.5 SAa: 07 16 13.0 +48 16 19 1.0 18 14.28 1(1) 0.2(0.2) 0.1
234-115 NOT H51 -19.3 07 16 52.3 +49 52 29 2.0 148 24 14.57 3(1) 0.9(0.2) 0.3
Abell 779
180-060 JKT98 H671 -19.7 Sa: 09 13 45.4 +34 50 14 1.3 58 17 14.36 7(1) 1.6(0.3) 1.1
Table 2: – continued
CGCG Run H Type R.A. (2000) Dec. a/b PA H flux H EW SFR
filter (h    m    s) (°   ′   ″) () (″) () (nm) (Myr)
181-007 NOT H51 -19.5 SA:a: 09 17 56.2 +34 30 34 1.2 139 19 14.65 4(1) 1.3(0.3) 0.7
181-012 NOT H51 -20.1 Sa: 09 18 34.0 +34 17 38 3.0 21 34 14.46 0(1) 0.1(0.2) 0.0
181-013 JKT94 H671 -20.6 Sb: 09 18 35.7 +34 33 11 4.7 153 43 14.13 3(1) 0.6(0.2) 0.5
181-016 NOT H51 -19.8 SBa 09 19 17.4 +34 00 29 1.8 35 30 13.92
181-017 NOT H53 -20.5 S:a: 09 19 22.4 +33 44 34 3.3 85 49 13.69
181-023 JKT94 H671 -20.5 S 09 19 41.4 +33 44 17 4.3 111 41 14.20 4(1) 0.9(0.2) 0.7
181-030 JKT94 H671 -20.1 SB:b 09 20 36.9 +33 04 29 2.7 3 28 14.24 6(1) 1.2(0.3) 0.9
181-032 JKT98 H674 -20.4 SBb 09 20 52.7 +35 22 06 1.1 98 30 13.31 20(3) 1.8(0.3) 3.4
181-045 NOT H51 -20.0 S:b: 09 27 16.0 +34 25 38 2.5 174 27 14.49 2(1) 0.4(0.2) 0.3
Abell 1367
126-074 JKT94 H671 -20.2 SBb pec 11 31 01.9 +20 28 21 1.7 88 24 13.54 35(3) 3.9(0.4) 5.0
126-075 JKT94 H671 -19.8 SB 11 31 03.7 +20 14 08 2.0 57 23 13.59
126-100 NOT H51 -20.3 SB:ab 11 34 53.5 +20 29 17 3.2 67 41 14.39 11(1) 3.0(0.3) 1.6
126-104 JKT98 H671 -19.8 SAB…pec 11 35 35.0 +20 30 19 2.3 116 25 14.67 16(1) 5.1(0.4) 2.3
127-002 NOT H53 -19.6 Sa pec 11 36 53.2 +21 00 15 1.4 47 21 14.40 8(1) 2.1(0.3) 1.2
97-026 JKT94 H671 -20.7 SBa pec 11 36 54.4 +19 58 15 1.8 8 27 13.43 70(5) 7.1(0.5) 10.1
97-027 JKT94 H671 -20.4 SB:a pec 11 36 54.2 +19 59 50 1.8 33 28 13.75 15(2) 2.0(0.3) 2.1
97-033 JKT94 H671 -19.9 S(B)a 11 37 36.0 +20 09 49 1.8 88 27 14.10 5(1) 1.0(0.2) 0.8
127-012A NOT H53 -21.2 Sc: 11 37 53.9 +21 58 53 3.4 106 72 13.19 6(3) 0.5(0.2) 0.9
127-012B NOT H53 -19.6 SAb 11 37 55.0 +21 59 08 1.3 1 19 14.30 18(2) 4.3(0.4) 2.6
127-016 NOT H53 -20.1 Sa: 11 39 16.2 +20 25 38 2.8 71 36 14.02 2(1) 0.3(0.2) 0.2
97-041 NOT H51 -19.7 SAa: 11 39 24.5 +19 32 04 1.3 78 22 14.25 6(1) 1.3(0.3) 0.8
127-025A JKT98 H671 -20.5 Sab: pec 11 40 44.2 +22 25 46 1.0 113 27 13.24 23(3) 1.9(0.3) 3.3
127-025B JKT98 H671 -19.8 S: 11 40 44.5 +22 26 48 2.5 56 29 13.97 21(2) 3.4(0.3) 2.9
97-062 JKT94 H674 -19.8 Sa: pec 11 42 14.8 +19 58 35 2.7 55 26 14.67 7(1) 2.3(0.3) 1.0
97-064 JKT94 H668 -19.5 SA0 11 42 14.6 +20 05 52 2.5 140 28 14.52
97-068 JKT94 H668 -20.6 SBc pec 11 42 24.5 +20 07 10 1.6 104 33 13.53 26(3) 2.9(0.3) 3.7
97-072 JKT98 H671 -20.4 SBab 11 42 45.2 +20 01 57 1.8 114 33 13.74 9(2) 1.2(0.3) 1.3
97-073 JKT94 H674 -19.4 SAcd: pec 11 42 56.4 +19 57 58 1.0 18 14.93 18(1) 7.4(0.5) 2.6
97-079 JKT98 H671 -19.3 S: pec 11 43 13.4 +20 00 17 1.6 108 17 15.38 24(1) 14.8(0.9) 3.5
97-087 JKT98 H671 -21.6 Sd pec 11 43 49.1 +19 58 06 6.3 134 67 13.28 80(5) 7.0(0.5) 11.4
97-091 JKT98 H674 -20.5 SABb 11 43 59.0 +20 04 37 1.4 54 30 13.58 27(3) 3.1(0.3) 3.9
97-092A JKT98 H671 -19.2 S0 pec 11 43 58.2 +20 11 06 1.6 14 15 15.19 10(1) 5.3(0.4) 1.5
97-093 JKT94 H668 -19.9 Sa: 11 44 01.9 +19 47 04 3.0 139 30 14.85 10(1) 3.6(0.3) 1.4
97-102A NOT H51 -19.9 Sa 11 44 17.2 +20 13 24 1.5 135 26 13.76 6(2) 0.9(0.2) 0.9
97-114 JKT94 H674 -19.2 S0/a: pec 11 44 47.8 +19 46 24 1.0 13 15.03 14(1) 6.1(0.4) 2.0
97-120A JKT94 H668 -20.9 SAab 11 44 49.2 +19 47 42 2.0 41 44 12.94 9(4) 0.6(0.2) 1.3
97-121 NOT H51 -20.8 SBb pec 11 44 47.1 +20 07 30 1.5 30 38 13.11 11(3) 0.8(0.2) 1.5
97-122 JKT94 H668 -20.7 Sb pec 11 44 52.2 +19 27 15 4.0 56 39 13.80 23(2) 3.2(0.3) 3.3
97-125 JKT94 H674 -19.8 Sa: pec 11 44 54.8 +19 46 35 1.2 69 25 14.14 8(1) 1.5(0.3) 1.1
97-129A NOT H50 -21.6 SABb 11 45 03.9 +19 58 25 1.8 73 65 12.43 27(6) 1.2(0.3) 3.9
127-045 JKT98 H671 -20.6 SAa 11 45 05.9 +20 26 18 1.2 40 30 13.31 6(3) 0.6(0.2) 0.9
127-046 JKT94 H674 -20.0 SB:bc pec 11 45 05.7 +21 24 42 2.2 128 28 14.28 9(4) 2.0(0.8) 1.3
97-129B NOT H51 -20.1 S:… 11 45 07.0 +19 58 01 2.3 113 31 14.59 5(1) 1.5(0.3) 0.7
97-138 NOT H50 -19.6 SAc 11 45 44.7 +20 01 52 1.0 19 15.00 15(1) 6.6(0.5) 2.1
127-049 JKT98 H671 -20.1 SBab 11 45 48.8 +20 37 43 3.3 65 33 14.50 16(1) 4.4(0.4) 2.3
127-050 NOT H51 -20.7 SBc 11 45 55.6 +21 01 32 1.1 179 39 13.24 15(3) 1.4(0.3) 2.2
127-051A NOT H53 -19.6 SB0/a 11 45 59.9 +20 26 20 1.8 124 25 14.11 14(2) 2.9(0.3) 2.1
127-051B NOT H53 -19.3 Sa pec 11 45 59.5 +20 26 50 2.0 150 19 14.74 6(1) 2.2(0.3) 0.9
127-052 JKT98 H671 -21.1 SA0 11 46 12.2 +20 23 30 1.6 7 48 12.61 9(5) 0.4(0.2) 1.3
127-055 JKT98 H671 -19.5 SAa 11 46 46.7 +21 16 17 1.0 14 14.19 18(2) 3.6(0.3) 2.5
97-149 NOT H51 -19.7 SAa: 11 47 15.0 +19 10 33 1.2 84 22 14.31 2(1) 0.6(0.2) 0.3
97-151 NOT H51 -19.8 Sa: 11 47 28.2 +18 03 13 3.5 25 26 15.06 2(1) 0.8(0.2) 0.2
97-152 NOT H51 -20.1 SBa: 11 47 39.3 +19 56 22 2.5 128 31 13.97 4(1) 0.7(0.2) 0.6
127-056 JKT94 H671 -20.1 Sb: 11 48 27.5 +21 09 23 3.3 79 31 14.66 5(1) 1.5(0.3) 0.7
127-062 NOT H51 -20.0 SB:a 11 49 30.3 +21 02 37 2.0 175 31 14.07 3(1) 0.5(0.2) 0.4
97-160 JKT94 H671 -19.4 S0/a 11 50 33.4 +17 51 29 1.2 81 17 13.85 2(2) 0.3(0.2) 0.3
127-067 JKT94 H671 -19.5 S? pec 11 50 39.5 +20 54 26 1.3 173 17 14.35 11(1) 2.5(0.3) 1.5
127-068 JKT94 H671 -19.7 S-Irr 11 50 52.7 +21 10 08 1.5 153 18 13.94 19(2) 3.1(0.3) 2.8
127-071 JKT94 H671 -19.4 S pec 11 50 55.4 +21 08 43 1.7 75 14 14.45 24(2) 6.2(0.5) 3.5
97-168 JKT98 H674 -20.1 Sbc: 11 51 48.4 +19 21 29 4.5 106 28 15.63 5(0) 3.7(0.3) 0.7
97-169 NOT H51 -20.7 Sc 11 51 52.5 +18 32 46 9.0 151 46 15.73 4(0) 3.7(0.3) 0.6
97-172 NOT H53 -19.7 SABb: 11 52 14.5 +18 39 03 2.0 165 22 15.25 4(1) 2.3(0.3) 0.6
Table 2: – continued
CGCG Run H Type R.A. (2000) Dec. a/b PA H flux H EW SFR
filter (h    m    s) (°   ′   ″) () (″) () (nm) (Myr)
97-174 NOT H53 -19.8 Sc: 11 52 43.9 +18 36 49 2.0 132 24 15.15 4(1) 2.1(0.3) 0.6
97-180 JKT94 H671 -19.4 Sab 11 54 13.9 +20 01 39 2.3 123 17 14.82 9(1) 3.2(0.3) 1.3
127-072 NOT H51 -20.8 SABbc 11 51 01.1 +20 23 57 1.0 35 13.30 17(3) 1.6(0.3) 2.5
127-073 NOT H51 -20.5 SBab 11 51 02.2 +20 47 59 1.0 34 13.35 8(2) 0.8(0.2) 1.1
127-082 NOT H51 -20.5 SAc 11 51 59.8 +21 06 30 1.3 121 28 13.61 21(2) 2.6(0.3) 3.0
127-083 NOT H51 -20.0 Sa 11 52 19.9 +21 06 08 1.3 153 22 13.83 6(2) 1.0(0.2) 0.9
127-085 JKT94 H671 -20.0 Sa 11 52 30.5 +20 37 32 3.0 73 28 14.35 4(1) 1.0(0.2) 0.6
127-090 NOT H51 -20.6 SBa 11 52 56.6 +20 28 45 1.0 31 12.98 4(3) 0.2(0.2) 0.5
127-095 JKT98 H668 -21.2 SBb 11 53 20.3 +20 45 06 1.2 97 44 12.60 41(6) 1.9(0.3) 5.8
127-096 NOT H51 -19.9 SAa 11 53 20.6 +21 01 18 1.2 85 23 13.84 5(2) 0.7(0.2) 0.7
127-100 NOT H51 -20.5 SBab 11 53 59.7 +20 34 21 1.4 29 32 13.49 7(2) 0.8(0.2) 1.0
Abell 1656
159-101 JKT98 H674 -19.4 Irr 12 52 48.9 +27 24 06 1.3 89 14 14.95 14(1) 5.7(0.4) 2.9
159-102 JKT98 H671 -20.9 Sab 12 52 53.6 +28 22 16 2.5 32 36 13.30 35(4) 3.1(0.3) 5.9
160-020 JKT98 H668 -19.2 Sa 12 56 06.1 +27 40 40 1.4 171 13 14.92 26(2) 10.3(0.6) 4.4
160-025 NOT H51 -21.1 SBa 12 56 27.8 +26 59 15 1.3 150 36 12.81 3(4) 0.2(0.2) 0.6
160-026 JKT98 H674 -19.5 S0/a: 12 56 28.5 +27 17 28 1.4 66 17 15.31 11(1) 6.2(0.5) 1.8
160-031 NOT H51 -20.1 Sa 12 56 49.7 +27 05 38 4.0 147 36 14.48 1(1) 0.3(0.2) 0.2
160-033 JKT98 H668 -19.6 E 12 56 51.2 +26 53 56 1.0 14 14.42 8(1) 2.0(0.3) 1.3
160-055 JKT98 H671 -21.2 SB:ab 12 58 05.6 +28 14 33 3.2 151 41 13.53 39(3) 4.3(0.4) 6.6
160-058 JKT98 H674 -20.2 S 12 58 09.3 +28 42 31 3.3 84 29 15.14 6(1) 2.9(0.3) 1.0
160-064 JKT98 H674 -19.5 pec 12 58 35.3 +27 15 53 1.2 69 15 15.18 10(1) 5.0(0.4) 1.7
160-067 JKT98 H674 -19.3 pec 12 58 37.3 +27 10 36 1.3 12 13 14.97 18(1) 7.4(0.5) 3.0
160-068 NOT H53 -20.5 (R’)SA0-? 12 58 35.2 +27 35 47 1.2 83 24 13.24 5(3) 0.4(0.2) 0.8
160-071 JKT H671 -19.4 S0/a 12 58 52.1 +27 47 06 1.8 133 20 14.81 21(1) 7.4(0.5) 3.5
160-072 JKT H668 -19.9 S0/a 12 58 48.5 +27 48 37 3.9 53 28 14.84 1(1) 0.2(0.2) 0.1
160-075 NOT H54 -19.4 pec 12 59 02.1 +28 06 56 1.2 31 14 14.93 13(1) 5.4(0.4) 2.1
160-078 NOT H51 -20.0 E/S0: 12 59 05.3 +27 38 40 1.1 79 20 14.34 6(1) 1.4(0.3) 1.0
160-099 JKT98 H668 -19.3 Sa: 12 59 40.1 +28 37 51 1.0 15 15.24 8(1) 4.1(0.4) 1.3
160-127 JKT98 H674 -19.3 pec 13 00 33.7 +27 38 16 1.4 65 13 15.38 7(1) 4.4(0.4) 1.2
160-130 JKT98 H674 -20.4 pec: 13 00 38.0 +28 03 27 3.3 151 30 14.62 13(3) 3.9(0.9) 2.2
160-132 JKT98 H674 -20.8 S 13 00 39.7 +29 01 10 2.0 56 36 13.61 14(2) 1.7(0.3) 2.4
160-139 NOT H51 -20.7 SB:ab 13 00 48.8 +28 09 30 1.1 39 31 13.15 5(3) 0.4(0.2) 0.9
160-147 NOT H51 -21.9 SBa 13 01 26.1 +27 53 10 1.1 2 67 12.06 22(8) 0.7(0.2) 3.7
160-148A JKT98 H671 -20.3 S pec 13 01 25.3 +29 18 50 1.7 125 27 13.85 19(2) 2.8(0.3) 3.1
160-148B JKT98 H671 -20.3 S pec 13 01 24.5 +29 18 30 1.0 27 12.91
160-150 JKT98 H674 -19.8 S pec 13 01 25.1 +28 40 37 1.5 110 19 14.70 2(1) 0.5(0.2) 0.3
160-154 JKT98 H671 -20.7 Sab 13 01 43.4 +29 02 40 3.0 85 33 14.23 8(1) 1.8(0.3) 1.4
160-156 JKT98 H671 -19.1 SA0 13 02 00.2 +27 46 58 2.0 52 14 14.72 2(1) 0.5(0.2) 0.3
160-158 JKT98 H671 -19.6 S0 pec? 13 02 07.9 +27 38 54 1.4 76 16 14.67 12(1) 3.7(0.3) 2.0
160-159 NOT H53 -20.9 Sa: 13 02 04.2 +29 15 12 4.5 156 49 13.47 2(2) 0.2(0.2) 0.3
160-160 JKT98 H674 -19.6 pec 13 02 12.8 +28 12 53 1.7 150 18 14.84 11(1) 4.0(0.4) 1.9
160-169 JKT98 H668 -19.4 S 13 03 05.9 +26 31 52 1.5 176 16 14.79 5(1) 1.7(0.3) 0.8
160-176A NOT H51 -22.1 Sab 13 03 49.9 +28 11 09 3.0 88 71 12.69
160-179 JKT98 H668 -19.8 S: pec 13 04 26.6 +27 18 16 1.5 65 21 14.98 16(1) 6.5(0.5) 2.6
160-180 JKT98 H674 -19.3 pec 13 04 22.8 +28 48 39 1.3 177 12 15.39 12(1) 7.2(0.5) 2.0
160-191 JKT98 H668 -20.5 pec 13 06 38.1 +28 50 53 1.8 169 32 14.60 23(2) 6.9(0.5) 3.9
160-193 JKT98 H674 -19.3 Sc+ 13 07 13.2 +28 02 49 1.1 165 14 14.94 9(1) 3.7(0.3) 1.6

Explanation of columns of Table 2.

Column 1. CGCG number (Zwicky et al. 1960–68). The numbering of CGCG galaxies in field 160 (Abell 1656) follows that of the SIMBAD data base, with an enumeration in order of increasing R.A.

Column 2. Observing run: JKT92, JKT94, JKT97 – Jacobus Kapteyn Telescope 1992 (service data), December 1994 and November 1997 respectively. NOT – Nordic Optical Telescope (5–8 January 2005).

Column 3. H filter used. (For transmission profiles, see Figures 1a and 1b.)

Column 4. Absolute B magnitude (see section 4.1)

Column 5. Galaxy type taken from Moss, Whittle & Pesce (1998); Moss & Whittle (2000, 2005). For galaxies for which no type is listed by these authors, the NED type is given (marked by in the Table).

Columns 6 & 7. R.A. and Declination (J2000) taken from NED.

Columns 8, 9 & 10. The major-to-minor axis ratio, position angle, and 24 mag arcsec isophotal radius respectively.

Column 11. R band apparent magnitude. The typical error in this measurement is mag.

Columns 12 & 13. H flux and EW within the R band 24 mag arcsec isophote. (Error is given in parentheses.)

Column 14. Global star formation rate (see section 4.4).

Table 2: – continued

4.1 Absolute B magnitudes

Absolute B magnitudes for the sample galaxies were calculated from CGCG photographic magnitudes. These magnitudes were converted to the system following RC3 and corrected for Galactic absorption using extinction maps of Schlegel et al. (1998) and the conversion of Cardelli et al. (1998). A correction was also applied for internal extinction, dependent on the inclination of the galaxy, as detailed in RC3. K-corrections were taken from Poggianti (1987) for the mean sample cluster redshift . Cluster distances were found from mean cluster recession velocities corrected to the centre of the local group following de Vaucouleurs et al. (1976), and assuming km . All sample galaxies were assumed to be cluster members, and the appropriate cluster distance was used to obtain the absolute magnitude.

4.2 Isophotal radii and R magnitudes

Following the methods of Koopmann, Kenney & Young (2001), an outer isophotal radius, , is defined at 24 mag in the R band. This provides a direct tracer of size or luminosity, and allows the normalisation of profiles of galaxies of different sizes or distances.

For the observed galaxies, the isophote was found by calculating the mean surface brightness of the annulus formed by each successive pair of apertures in the R band growth curves; this is then set to be the local surface brightness at the mean semi-major axis of each annulus. Linear interpolation between points gives the semi-major axis at which the local surface brightness first drops below 24 mag .

The apparent magnitude, , corresponds to the integrated R band light out to the isophote. The uncertainty in this magnitude arising from errors associated with sky and other background subtraction and calibration is typically quite small (). This magnitude was taken as the global value for a galaxy in the subsequent analysis.

It is to be noted that , determined in the above manner, underestimates the total luminosity from the galaxy, since light from outer isophotes fainter than mag has been omitted. A study was made, by comparison with the HGS field sample, to estimate how large is this effect. HGS galaxy R band magnitudes were measured in apertures set such that the enclosed flux varied by less than 0.5% over three consecutive points in the growth curve. The total magnitude was compared with , the magnitude at , calculated for the HGS sample in the same way as for the cluster data. Total R band magnitudes are typically found to be mag brighter than those measured at .

4.3 H flux and EW

The H flux is the integrated H flux out to the isophote; the EW is this integrated flux divided by the corresponding R band flux density to the same isophotal limit. It is to be noted that the EW normalises the star formation rate to the underlying older stellar population, thus providing a measure of the specific star formation rate (i.e. the star formation rate per unit mass). Kennicutt (1998) found that only high mass ( M) and therefore short-lived ( Myr) stars made any significant contribution to integrated ionising flux, so EW is a measure of the importance of current or very recent star formation relative to the star formation history of the galaxy.

Errors in the H flux and EW associated with sky and other background subtraction and calibration are typically small ( in flux; and in EW respectively). In contrast, the largest single source of error for both flux and EW comes from the determination of the scaling factor used to subtract the continuum from the H data. The continuum scaling errors were found to depend strongly on EW. Figure 2 shows the percentage error on H fluxes and EWs, due to a 1 change in continuum scaling factor. The points are well fit by a power law, and this has been used in the calculation of individual galaxy errors. These errors range from 4% for the highest EW objects to for those with very low EWs, although the uncertainties are less than 25% for most galaxies within the sample.

Figure 2: Continuum scaling errors as a function of EW.

A number of galaxies in the current sample are found in the literature as part of other studies. H fluxes for 32 objects and EWs for 24 are given in Moss, Irwin & Whittle (1988) (MWI88). A later paper (Moss et al. 1998) (MWP98), based on similar observations in Abell 1367, includes further data for 18 galaxies. Thirty objects in our sample are included in an H imaging survey by Gavazzi et al. (1998) (GAV98), 29 in a large aperture photometry survey in the Cancer, Abell 1367, and Coma clusters (Kennicutt, Bothun & Schommer 1984) (KBS84), 15 in a deep H survey of galaxies in Abell 1367 and Coma by Iglesias-Páramo et al. (2002) (IP02), a further 7 in a study of spiral galaxies in the Coma and Hercules superclusters and the Cancer cluster (Gavazzi, Boselli & Kennicutt 1991) (GBK91), and one object in a survey of star formation in spiral galaxies by Romanishin (1990) (Rom90).

Figure 3 (top) shows a comparison between published H fluxes and those found in the present survey. The flux values taken from the literature are uncorrected for extinction effects. Therefore the Galactic extinction corrections applied to the data in the present survey were removed for comparison purposes. No correction has been made for the satellite [NII] lines in any of the comparison data; however the KBS84 and GBK91 fluxes and EWs have been multiplied by 1.16 as suggested by Kennicutt et al. (1994) and Gavazzi et al. (1998) to account for an overestimate of continuum flux in these data, due to the telluric absorption feature near 6900 Å in their red continuum side-band. The solid line shows a one-to-one correlation, which is a good fit to the data. The rms scatter in from 101 comparison measures is 0.18

Figure 3: Comparison of total H fluxes (top) and EWs (bottom) obtained in this study with values in the literature.

A comparison of calculated EWs with 95 values from the literature is shown in Figure 3 (bottom). Again a one-to-one correlation (solid line) shows good agreement with an rms scatter of 0.20 in .

No corrections have been made to account for the different aperture sizes used in the comparison studies, or for the fact that the total fluxes and EWs in this study are taken at . The true total fluxes are therefore likely to be slightly larger than the literature and current values shown here, as these apertures may not be detecting all of the H emission from the galaxies. In a similar manner as for the R magnitudes (see section 4.2 above), a study was made, by comparison with the HGS field sample, to estimate how large is this effect. It was found that H flux values are typically lower than corresponding total values for HGS galaxies.

4.4 Star formation rates

Cluster distances (see section 4.1) were used to convert H + [NII] fluxes into luminosities. These latter were corrected for internal extinction using a constant value of 1.1 mag (Kennicutt 1983). Following Kennicutt & Kent (1983) a further correction was made to account for the [NII] doublet that lies within the H filter bandpasses. Corrected H luminosities were then converted to star formation rates (SFRs) using the relation,

(Kennicutt, Tamblyn & Congdon 1994), which assumes a Salpeter IMF (Salpeter 1955) with masses ranging from 0.1 to 100 .

Finally, it may be noted that the correction that was made to the H luminosity for contamination by the [NII] doublet depends only on galaxy type, not on luminosity. As is well known, lower luminosity galaxies tend to be less metal-rich than their more luminous counterparts (e.g. Zaritsky, Kennicutt & Huchra 1994; Miller & Hodge 1996); this leads to the expectation of a lower [NII]/H ratio with decreasing galaxy luminosity, which is indeed confirmed observationally (e.g. Jansen et al. 2000; Gavazzi et al. 2004). However, the galaxies in the current dataset cover a relatively narrow magnitude range, brighter than . Furthermore, both Jansen et al. (2000) and Gavazzi et al. (2004) find no significant variation in the [NII]/H ratio within this magnitude range. Thus neglect of any dependence of the [NII]/H on galaxy luminosity for the correction to H luminosities (and hence SFRs) for the present galaxy sample appears to be justified.

5 Completeness of the Objective Prism Survey

The current dataset is for a subsample of galaxies included in the H objective prism survey (OPS) undertaken by Moss and colleagues (see Moss & Whittle, 2000, 2005). Moss et al. (1998) estimated that ELG detection for the OPS was 90% complete above 20 Å(2 nm) EW, and 17% complete below this limit. However these estimates were based on a comparatively small sample of 35 galaxies, for which photoelectric data were available. By contrast, the current CCD dataset includes a complete sample of Sa–Sc galaxies () in six of the eight OPS clusters, of which 43% () were detected as emission-line galaxies (ELGs) by the OPS. This sample may be used to provide a better determination of the completeness of the OPS, as follows.

The distribution of ELGs and non-ELGs for the Sa–Sc complete sample with both H EW and flux are shown in Figures 4 and 5 respectively. As is seen from Figure 4, EW is a relatively poor discriminant between ELGs and non-ELGs: while 63% of galaxies are detected as ELGs above 2 nm, some 30% of galaxies are detected below this limit.

Figure 4: Distribution of H EWs for the complete Sa–Sc sample (open histogram) and those detected by the objective prism survey as having diffuse (hashed histogram) or compact (solid histogram) emission. The total shaded area shows the total number of galaxies detected by the objective prism survey.
Figure 5: As Figure 4 for H flux values. There are no objective prism survey (OPS) detections with . Galaxies identified by the OPS as having diffuse emission (hatched histogram) have a lower mean flux value than those classified as compact (solid histogram).

By contrast, H flux appears as a rather better discriminant: below a flux limit, (), no galaxies were detected in emission by the OPS; above this limit, the detection efficiency is 49%, rising to 67% for galaxies with the strongest H flux, ().

However the mean H surface brightness appears to be a better discriminant than either EW or flux. In Figure 6 we show distributions of ELGs and non-ELGs with mean H surface brightness, where is the area of the ellipse centred on the galaxy bounded by the 24 mag isophote. Below a limit, (), only 4 out of 41 galaxies ( 10%) were detected as ELGs by the OPS; above this limit, 63% were detected, rising to 85% above the limit ().

Figure 6: As Figure 4 for H surface brightness values. Detections of galaxies by the objective prism survey (OPS) fall off rapidly fainter than . Galaxies identified by the OPS as having compact emission (solid histogram) have a higher mean surface brightness than those with diffuse emission (hatched histogram).

In Figures 4, 5, and 6 detected ELGs are shown as compact or diffuse following their classification by the OPS (for further details, see Moss & Whittle 2000). Compact ELGs have higher H EW, flux, and surface brightness than diffuse ELGs, but there is a broad overlap of all these values between the two ELG types. In particular, H mean surface brightness is not able to discriminate well between compact and diffuse emission since this mean surface brightness is based on a generally larger scale (viz. the isophote) than the smaller scale features visually classified by the OPS. Further discussion of the H surface brightness distribution for individual galaxies, and comparisons of these distributions between field and cluster galaxies will be given in a subsequent paper (Bretherton et al., in preparation).

6 Conclusions

H and R band continuum CCD observations have been completed for a sample of 227 CGCG galaxies associated with 8 low-redshift Abell clusters, which were the subject of an objective prism survey (OPS) by Moss and collaborators (Moss et al. 1998; Moss & Whittle 2000, 2005). The sample galaxies were generally restricted to those with velocities within 3 of the cluster mean, and known AGN have been excluded. R band magnitudes, H fluxes and EWs, and star formation rates for the sample are listed in Table 2.

The dominant constraint on the detection efficiency of emission-line galaxies (ELGs) by the OPS is shown to be H surface brightness. Detection of ELGs is 85%, 70%, and 50% complete at the mean surface brightness values of , , and W m arcsec respectively, where the mean H surface brightness was measured within the R band isophote of 24 mag for the galaxy.

The present data, together with matched sets of data from a recent H galaxy survey of UGC galaxies within km (HGS, Shane 2002; James et al. 2004) will be used for a forthcoming comparative study of R band and H surface photometry between cluster and field spirals (Bretherton et al., in preparation).

Acknowledgments

This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We thank Anna Hodgkinson for assistance with data preparation for the paper.

Footnotes

  1. offprints: C. F. Thomas

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