Mean Redshift Research Articles

The Cluster of Compact Galaxies ZW CL 0152+33

Redshifts have been determined for 14 seventeenth-magnitude, mostly red, compact galaxies which form an elongated system at the center of the cluster Zw Cl 0152+33. This cluster was discovered by Zwicky to contain a vast preponderance of compact galaxies and, in this respect, is very unusuaL The mean redshift is 26,304 km s ' and the apparent distance modulus of the cluster is (`n - M) = 38.2. The brightest galaxy in the cluster, which is a compact galaxy according to Zwicky, has Mp = -21.2. All the observed galaxies except one have late-type absorption spectra; the remaining galaxy is blue and has an emission-line spectrum. It is argued that the galaxies in the elongated system do not form a linear chain, but are in a flattened system seen nearly edge-on. An application of the virial theorem is complicated by the fact that the galaxies on the outer parts of the region considered have a higher velocity dispersion <r than those in the center. As a result we find that the center of the cluster is probably a bound system while the outer members are escaping from the cluster on a timescale of about 10 years. This is smaller by a factor of 100 than the estimated dynamical relaxation time in the cluster; as a result the overall dynamics of the cluster are not understood.

The Correlation of Redshift with Magnitude and Morphology in the Coma Cluster

view Abstract Citations (63) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Correlation of Redshift with Magnitude and Morphology in the Coma Cluster Tifft, W. G. Abstract Redshifts and magnitudes for nearly 100 galaxies in the core of the Coma cluster are now available. The sample is nearly complete to seventeenth magnitude for the nuclear regions (central 4'.'8 spot). Nearly all the higher-redshift galaxies in the Coma cluster are nonellipticals. The separation of the ellipticals from the nonellipticals is significant in both the redshift and magnitude coordinates and is shown to be a maximum in a linear combination of redshift and magnitude along a direction sloping close to 0.6 mag fainter per 1000 km s-1 increase in redshift. The morphological separation is in the same sense as the pattern in the Virgo cluster. When the redshift-magnitude diagram is examined in the direction of the maximum morphological separation, it is shown to have a strongly banded structure which is not present in any other direction. The observed redshift-magnitude pattern is compared with an outlying distinct group of galaxies in the Coma cluster which shows a nearly identical pattern slightly shifted in redshift. The pattern is also used to predict the (m, log s)-diagram for field galaxies. Observed field galaxies are shown to fit the predicted pattern and to deviate from the normal velocity-dispersion model. After allowance for magnitude and redshift uncertainties it is shown that residual true Doppler velocity dispersion in the Coma cluster cannot exceed about 220 km 1, and the cluster is not dynamically unstable. In the presence of an intrinsic unexplained redshift which produced the observed pattern, the mean redshift of a group of galaxies need not be the same as the Hubble velocity of the cluster. Systematic trends in the deviation of the Hubble velocity from the mean redshift are possible due to selection with distance and may explain the local apparent dependence of the Hubble constant on distance. Publication: The Astrophysical Journal Pub Date: August 1972 DOI: 10.1086/151584 Bibcode: 1972ApJ...175..613T full text sources ADS | data products SIMBAD (88) NED (87)

Atomic-beam study of the solar 7699 Å potassium line and the solar gravitational red-shift

The shape and red-shift of the solar potassium resonance line (42 P 1/2→42 S 1/2) at 7699 A have been studied by an atomic-beam resonant scattering technique. Light from the central 10% of the solar image fell on a potassium atomic beam whose scattering wavelength was shifted in a known way by a magnetic field. The line profile was obtained by measuring the scattered light intensity as a function of magnetic field. The time required for a single profile of the line core was 30–40 min. Most of the observed profiles were asymmetrical and the character of the asymmetry varied in an erratic way from profile to profile. The mean red-shift of the 40 profiles which showed small or no asymmetry was: (δλ)mean = 10 ± 1 mA = (0.61±0.06)(δλ)gravwhere (δλ grav) is the gravitational red-shift predicted on the basis of the principle of equivalence. This result, together with those of other recent experiments, is consistent with the previously observed correlation between the red-shift of a solar line and its strength. Various checks of the experimental method are discussed, including preliminary measurements on the solar sodium D1 line.

A Spectroscopic Survey of Compact and Peculiar Galaxies

view Abstract Citations (288) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Spectroscopic Survey of Compact and Peculiar Galaxies Sargent, Wallace L. W. Abstract Low-dispersion spectrograms have been obtained for 141 objects in Zwicky's first five lists of compact galaxies. These 141 objects were largely but not completely selected for their blue appearance on the Sky Survey prints. Direct photographs were obtained at the 200-inch prime focus of a representative sample of thirty objects. Photoelectric observations were made for forty4our galaxies. The spectra show ten objects to have Seyfert-like emission lines; thirty-three to have sharp emission lines; twenty to have both absorption lines and sharp emission lines; sixty to have absorption lines; and three to have continuous spectra. The remaining objects were galactic stars and one planetary nebula. The UBV colors of the galaxies are correlated with the spectra. Individual descriptions of the 126 galaxies, including their redshifts and absolute magnitudes, are given. The mean redshift is 9994 km , and the mean absolute magnitude is Mp = -20.2. The galaxies are a very heterogeneous collection with a range in absolute magnitude -14.9> Mp> -23.2. The galaxies with sharp emission lines are probably excited by hot stars. Many new interesting objects are described, including field galaxies with high intrinsic luminosities, four new Seyfert galaxies, a new "ring" galaxy, and several dwarf galaxies with very strong, sharp emission lines. We show that the galaxies for which 200-inch photographs were obtained are indeed compact in the sense of having an abnormally high luminosity per square parsec. Publication: The Astrophysical Journal Pub Date: May 1970 DOI: 10.1086/150443 Bibcode: 1970ApJ...160..405S full text sources ADS | data products NED (140) SIMBAD (2)

The Stellar Content and Distance of the Galaxy NGC 2403 IN the M81 Group

view Abstract Citations (322) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Stellar Content and Distance of the Galaxy NGC 2403 IN the M81 Group Tammann, G. A. ; Sandage, Allan Abstract Fifty-nine variables have been found in the nearby Sc galaxy NGC 2403, which is a member of the M81 group. Of these, seventeen are Cepheids ranging in period from 87448 to 2O~23O; eight are very bright irregular blue variables of the type previously found in M31 and M33; seventeen are bright, red irregular supergiant variables similar to those in h and x Per; there is one eclipsing binary; and sixteen are unclassified variables of undetermined nature. NGC 2403 is the first galaxy outside the Local Group in which Cepheids have been detected. Light-curves have been determined relative to a photoelectric sequence of seventy-three stars which covers the interval from B = 9.15 to B = 22.70, V = 8.39 to V = 21.80. Three-color photoelectric observations of the sequence stars brighter than V = 19.5 show that the local reddening due to the galactic system is E(B - V) = 0.06 mag. The period-luminosity relations for Cepheids in B and V at maximum light provide two well-determined upper envelope fits to the standard P-L function, giving apparent distance moduli of NGC 2403 of (m - M)AB = 27.80 ± 0.1 and (m - M)AV = 27.75 ± 0.1. These reduce to true moduli of (m - M)o,B = 27.56, and (m - M)oy = 27.57 from the Cepheids alone. Four other distance indicators give closely comparable values. (1) Star counts across the face of NGC 2403, corrected for foreground contamination, give B = 18.25 for the brightest resolved stars. Previous calibration of MB = -9.3 in galaxies of the Local Group gives (m - M)AB = 27.55. (2) The brightest blue irregular variable occurs at B(max) = 18.2, giving (m - M)AB =27.5 ± 0.2 if MB(max) = -9.3 is adopted from M31 and M33. (3) The brightest irregular red variable occurs at V(max) = 19.98, B(max) = 22.02. Calibration via the LMC, NGC 6822, and the SMC gives a preliminary value of Mv(max) = -8.00, MB(max) = -6.00 for these stars, giving apparent moduli of (m - M)AB = 28.02, and (m - M)AV = 27.98. (4) The angular sizes of the largest, and mean of the first five largest Hii regions, calibrated via the LMC and M33, give (m - M)O,L = 27.54 ± 0.18 and (m - M)0,5 = 27.52 ± 0.40. The average of all methods is given in Table 12 as (m - = 27.55 ± 0.13 (AD). The agreement between the methods is good and provides evidence that no systematic difference exists from galaxy to galaxy among the various distance indicators. One unexpected result is that the red supergiants, both constant and variable, may be a new and pre- cise distance indicator. There appears to be an upper envelope to the absolute luminosity of these stars at about M~ = -8.0. Such red stars can be located with ease in all Sc and Irr galaxies with (m - M)AV <29 by comparing red and blue plates and, therefore, they can be important in an intermediate step for the redetermination of the Hubble constant. The ratio of mean redshift of the M81 group-each galaxy corrected individually for solar motion- to the distance to NGC 2403 of r = (3.25 ± 0.20) X 106 pc iS v/r = (65 ± 15) km sec' Mpc'. This is not claimed to have any relation to the Hubble constant because the sample contains only one group, but similar analysis of many additional groups may eventually lead to an adequate value of H Publication: The Astrophysical Journal Pub Date: March 1968 DOI: 10.1086/149487 Bibcode: 1968ApJ...151..825T full text sources ADS | data products NED (74) SIMBAD (10)

Absorption Line Spectrum of the Quasi-stellar Object 3C 191

BAHCALL1 has pointed out that in the absorption line spectrum for ions in the gaseous envelope of 3C 191, there is a correlation between the ionization potential and Δz, the difference between z (the red-shift of the absorption line spectrum for any ion) and zem (the mean red-shift of the emission line spectrum). Fig. 1 indicates, as a set of vertical lines, the spread in Δz values derived from curves fitted by Burbidge and Lynds2 to four sets of measurements3,4. In the figure, the ionization potential plotted is that of the atom or ion having one more electron than the absorbing ion; while Δz is defined as zem−z.