Recession Velocity Research Articles

Coordinate confusion in conformal cosmology

Abstract A straightforward interpretation of standard Friedmann–Lemaître–Robertson–Walker (FLRW) cosmologies is that objects move apart because of the expansion of space, and that sufficiently distant galaxies must be receding at velocities exceeding the speed of light. Recently, however, it has been suggested that a simple transformation into conformal coordinates can remove superluminal recession velocities, and hence the concept of the expansion of space should be abandoned. This work demonstrates that such conformal transformations do not eliminate superluminal recession velocities for open or flat matter-only FLRW cosmologies, and all possess superluminal expansion. Hence the attack on the concept of the expansion of space based on this is poorly founded. This work concludes by emphasizing that the expansion of space is perfectly valid in the general relativistic framework; however, asking the question of whether space really expands is a futile exercise.

On the Phenomenology and Mechanics of Super Plastic Flow in Advanced Structural Materials

In connection with ancient and recent view on cosmology, it is interesting to note that our universe could be a spherical crystal and it moves as a crystal in a relative position with others spherical universes, where the Burgers vector for cellular dislocations dynamics is the Hubble length: λH=1.32x1026m. The expansion process of this polycrystalline spatially extended system obey the hyperbolic granular flow, which it is due to an accelerated motion manifested during the deformation process of super plastic advanced structural universes in a similar behaviour of super plastic advanced structural materials. Consequently, in this work the phenomenology and mechanics of super plastic flow are analyzed in the context of the unified interpretation of Hubble flow, plastic flow and super plastic flow, where the combination of fundamentals constants with the natural Planck length, allows obtain in a closed agreement with the Orowan equation the magnitude of the nature Burgers vector of dislocation in the cosmic structure for the universe as follow: 1.62 10 . 35 3 0 x m c H G b P − ⊥ ⊥ ⊥ = = = = h λ ρ ν Where, b⊥ = magnitude of the nature Burgers vector for the universe (b⊥ = 1.62x10-35m), λP = Planck length (λP = 1.62x10-35m), H0 = the Hubble parameter (H0=70 (km/sec)/Mpc = 2.26854593 x10-18s-1), ρ⊥ = dislocation density (ρ⊥ = 1.273x1011 dislocations/m2) in the universe. ν⊥ = the recession velocity of galaxies related with dislocations dynamics in the cosmic structure (ν⊥ = 1100x103 m/s, it is the recession velocity of the Virgo super cluster at 16 Mpc distance). h = h / 2π . Here h = the Planck constant (h = 6.6262x10-34 Joule-s), G = the Newtonian constant (G = 6.67259x10-11 m3/kg s2) and c = the speed of light (c = 299 792 458 m/s) [1-3].

Space‐time curvature and recession velocities

AbstractThe problem of interpretation of recession velocities reflects straightforwardly the curvature of space‐time. In a recent article it was claimed that this problem would show that the General Relativity Theory had to and would overrule the Special Relativity Theory (Davis & Lineweaver 2003; Lineweaver & Davis 2005). This must be corrected. It is shown that the simplistic definition of the recession velocity as change in distance on a space of constant cosmological time yields in fact a pseudo‐euclidean angle and that the simplest correct definition of the recession velocity fits perfectly with the SRT formula for the Doppler effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Minor Galaxy Interactions: Star Formation Rates and Galaxy Properties

We study star formation in a sample of 1204 galaxies in minor ( ≥ 2) pair and compact groups, drawn from the Sloan Digital Sky Survey Data Release 5. We analyze an analogous sample of 2409 galaxies in major ( < 2) pair and compact groups to ensure that our selection reproduces previous results, and we use a field sample of 65,570 galaxies for comparison. Our major and minor pair samples include only galaxies in spectroscopically confirmed pair, where the recessional velocity separation ΔV < 500 km s-1 and the projected spatial separation ΔD < 50 kpc h-1. The relative magnitude (a proxy for the mass ratio) of the pair is an important parameter in the effectiveness of the tidally triggered star formation in minor interactions. As expected, the secondary galaxies in minor pair show evidence for tidally triggered star formation, whereas the primary galaxies in the minor pair do not. The galaxy color is also an important parameter in the effectiveness of triggered star formation in the major galaxy pair. In the major pair sample, there is a correlation between the specific Hα star formation rate (SSFR) and ΔD in the blue primary and blue secondary galaxies; for the red primary and red secondary galaxies, there is none. Galaxies in pair have a higher mean SSFR at every absolute magnitude compared to matched sets of field galaxies, and the relative increase in mean SSFR becomes larger with decreasing intrinsic luminosity. We also detect a significantly increased AGN fraction in the pair galaxies compared to matched sets of field galaxies.

NGC 5011C: An Overlooked Dwarf Galaxy in the Centaurus A Group

A critical study of the properties of groups of galaxies can be done only once a complete census of group members is available. Despite extensive surveys, even nearby groups can lead to surprises. Indeed, we report the discovery of a previously unnoticed member of the Centaurus A Group, NGC 5011C. While the galaxy is a well-known stellar system listed with a NGC number, its true identity has remained hidden because of coordinate confusion and wrong redshifts in the literature. NGC 5011C attracted our attention since, at a putative distance of 45.3 Mpc, it would be a peculiar object with a very low surface brightness typical of a dwarf galaxy and, at the same time, a size typical of an early-type spiral or S0 galaxy. To confirm or reject this peculiarity, our immediate objective was to have the first reliable measurement of its recession velocity. The observations were carried out with EFOSC2 at the 3.6 m European Southern Observatory (ESO) telescope, and the spectra were obtained with the instrument in long-slit mode. The redshifts of both NGC 5011C and its neighbor NGC 5011B were computed by cross-correlating their spectra with that of a radial velocity standard star. We found that NGC 5011C indeed has a low redshift of v⊙ = 647 ± 96 km s-1 and thus is a nearby dwarf galaxy rather than a member of the distant Centaurus cluster, as believed for the past 23 years. Rough distance estimates based on photometric parameters also favor this scenario. As a by-product of our study we update the redshift for NGC 5011B to v⊙ = 3227 ± 50 km s-1. Applying population synthesis techniques, we find that NGC 5011B has a luminosity-weighted age of 4 ± 1 Gyr and a solar metallicity, and that the luminosity-weighted age and metallicity of NGC 5011C are 0.9 ± 0.1 Gyr and 1/5 solar. Finally, we estimate a stellar mass of NGC 5011C comparable to that of dwarf spheroidal galaxies in the Local Group.

Is Space Really Expanding? A Counterexample

In all Friedman models, the cosmological redshift is widely interpreted as a consequence of the general-relativistic phenomenon of expansion of space. Other commonly believed consequences of this phenomenon are superluminal recession velocities of distant galaxies, and the distance to the particle horizon greater than ct (where t is the age of the Universe), in apparent conflict with special relativity. Here, we study a particular Friedman model: empty universe. This model exhibits both cosmological redshift, superluminal velocities and infinite distance to the horizon. However, we show that the cosmological redshift is there simply a relativistic Doppler shift. Moreover, apparently superluminal velocities and ‘acausal’ distance to the horizon are in fact a direct consequence of special-relativistic phenomenon of time dilation, as well as of the adopted definition of distance in cosmology. There is no conflict with special relativity, whatsoever. In

Becoming Classical: A Possible Cosmological Influence on the Quantum-Classical Transition.

Although cosmic expansion at very small distances is usually dismissed as entirely inconsequential, it appears that these extraordinarily small effects may in fact have a real and significant influence on our world. Calculations suggest that the minute recessional velocities associated with regions encompassed by extended bodies may have a role in creating the distinction between quantum and classical behavior. Using an uncertainty in position estimated from the spread in velocities associated with its size, the criterion that the uncertainty in position should be smaller than the extension of the object leads to a threshold size that could provide a fundamental limit distinguishing the realm of objects governed by classical laws from those governed by quantum mechanics.

Laser Pulse Heating of Steel Surface: Consideration of Phase-Change Process

Laser pulse heating and the phase-change process taking place in the region irradiated by a laser beam are considered. A numerical method is employed to predict temperature field and recessing velocities of evaporating and melting surfaces. An experiment is conducted to compare the cavity size obtained from experiment with the prediction. The prediction of the recession velocity of the evaporating surface is compared with the results of a one-dimensional closed-form solution. It is found that the mushy zones at the solid–liquid and liquid–vapor interfaces are visible at some depth below the irradiated surface. The recession velocity of the evaporating front velocity follows almost the temporal variation of the laser heating pulse; moreover, recession velocity of the solid–liquid interface is higher than that corresponding to the liquid–vapor interface. The cavity shape predicted from the present simulation agrees well with experiment. In addition, the prediction of the recession velocity of the evaporating surface agrees well with the closed-form solutions.

Laser heating: jet emanating from laser induced cavity

Laser heating of steel surface and cavity formation during laser irradiation pulse are investigated. The recession of the solid surface due to melting and evaporation is modeled using an energy method. Jet emerging from the laser induced cavity and expanding into stagnant water, resembling laser shock processing, is also simulated. Governing flow equations are solved numerically using a control volume approach employing a moving mesh in the solution domain. This is because of the recessing surfaces of the vapor, liquid and solid phases during the heating pulse. It is found that mushy zone size at liquid–vapor interface is larger than that of at solid–liquid interface. Expansion of the vapor jet, emanating from the cavity and expanding into stagnant water ambient, is high in the axial direction in the early heating period, and as the time progresses the radial expansion of the jet becomes visible due to pressure build up in the jet frontal area. Considerably high recoil pressure is developed in the cavity due to high recession velocity of cavity surface and expansion velocity of vapor jet.

AGES Observations of Abell1367 and its Outskirts

AbstractThe Arecibo Galaxy Environment Survey (AGES, Auld et al. 2006) will map ~200 square degrees over the next years using the ALFA feed array at the 305-m Arecibo Telescope. AGES is specifically designed to investigate various galactic environments from local voids to interacting groups and cluster of galaxies. AGES will map 20 square degrees in the Coma-Abell1367 supercluster including the Abell cluster 1367 and its outskirts (up to ~2 virial radii). In Spring 2006 we nearly completed the observations of 5 square degrees in the range 11:34&lt; RA&lt; 11:54, 19:20&lt;Dec&lt;20:20 covering all the cluster core and part of its infalling region reaching a 5 sigma detection limit of M(HI)~4×108M⊙ (assuming a velocity width ~200 km~s−1) at the distance of Abell1367 (~92 Mpc). An HI selected sample has been extracted from the datacube obtaining a catalogue of fluxes, recessional velocities, positions and velocity widths. We present a preliminary analysis of the properties of the HI sources and report the discovery of HI diffuse features within interacting groups at the periphery of Abell1367.

Gaseous tidal debris found in the NGC 3783 group

We have conducted wide-field Hi mapping of a ∼5.5 x 5.5-deg 2 region surrounding the NGC 3783 galaxy group, to an Hi mass limit of ∼4 x 10 8 M ⊙ . The observations were made using the multibeam system on the Parkes 64-m radiotelescope, as part of the Galaxy Evolution Multiwavelength Study. We find twelve H I detections in our Parkes data, four more than catalogued in H I Parkes All Sky Survey (HIPASS). We find two new group members, and discover an isolated region of H I gas with an Hi mass of ∼4 x 10 8 M ⊙ , without a visible corresponding optical counterpart. We discuss the likelihood of this Hi region being a low surface brightness galaxy, primordial gas, or a remnant of tidal debris. For the NGC 3783 group we derive a mean recession velocity of 2903 ± 26 km s -1 , and a velocity dispersion of 190 ± 24km s -1 . The galaxy NGC 3783 is the nearest galaxy to the luminosity-weighted centre of the group, and is at the group mean velocity. From the X-ray and dynamical state of this galaxy group, this group appears to be in the early stages of its evolution.

Determination of the Hubble Constant, the Intrinsic Scatter of Luminosities of Type Ia Supernovae, and Evidence for Nonstandard Dust in Other Galaxies

A sample of 109 type Ia supernovae (SNe Ia) with recession velocity < 30,000 km s^{-1}, is compiled from published SNe Ia light curves to explore the expansion rate of the local Universe. Based on the color parameter delta C_{12} and the decline rate delta m_{15}, we found that the average absorption to reddening ratio for SN Ia host galaxies to be R_{UBVI} = 4.37+/-0.25, 3.33+/-0.11, 2.30+/-0.11, 1.18+/-0.11, which are systematically lower than the standard values in the Milky Way. We investigated the correlations of the intrinsic luminosity with light curve decline rate, color index, and supernova environmental parameters. In particular, we found SNe Ia in E/S0 galaxies to be brighter close to the central region than those in the outer region, which may suggest a possible metallicity effect on SN luminosity. The dependence of SN luminosity on galactic environment disappears after corrections for the extinction and delta C_{12}. The Hubble diagrams constructed using 73 Hubble flow SNe Ia yield a 1-sigma scatter of <0.12 mag in BVI bands and ~0.16 mag in U band. The luminosity difference between normal SNe Ia and peculiar objects (including SN 1991bg-like and 1991T-like events) has now been reduced to within 0.15 mag via delta C_{12} correction. We use the same precepts to correct the nearby SNe Ia with Cepheid distances and found that the fully corrected absolute magnitudes of SNe Ia are: M_{B} = -19.33+/-0.06 mag, M_{V} = -19.27+/-0.05 mag. We deduced a value for the Hubble constant of H_{0} = 72 +/- 6 (total) km s^{-1} Mpc^{-1}.

Einstein’s Mistakes

Science sets itself apart from other paths to truth by recognizing that even its greate practitioners sometimes err.

Constraints on hot metals in the vicinity of the Galaxy

We have searched for evidence of soft X-ray absorption by hot metals in the vicinity of the Galaxy in the spectra of a small sample of 15 type I active galactic nuclei (AGN) observed with the high-resolution X-ray gratings on board Chandra. This is an extension of our previous survey of hot O vii and O viii absorbing gas in the vicinity of the Galaxy. The strongest absorption signatures within a few hundred km s−1 of their rest-frame energies are most likely to be due to warm absorbing outflows from the nearest AGN, which are back-lighting the local hot gas. We emphasize that absorption signatures in the spectra of some distant AGN that are kinematically consistent with the recessional velocity of the AGN are most likely to be due to hot local gas. Along the sightline towards PG 1211+143, PDS 456 and MCG–6-30-15 there is a very large absorbing Fe column density which is kinematically consistent with absorption by hot, local Fe. The sightlines to these three AGN pass through the limb of the Northern Polar Spur (NPS), a local bubble formed from several supernovae which, if rich in Fe, may account for a large local Fe column. We obtain limits on the column density of local, highly ionized N, Ne, Mg, Si along all of the sightlines in our sample. We correlate the column density limits with those of highly ionized O along the same sightlines. Assuming the hot local gas is in collisionally ionized equilibrium, we obtain limits on the temperature and relative abundances of the metals in the hot local gas. Our limits on the ionic column densities in the local hot gas seem to be consistent with those observed in the hot halo gas of edge-on normal spiral galaxies.

The active galaxy NGC 3862 in a compact group in the cluster A1367

We study a compact group of 18galaxies in the cluster A1367 with redshifts z =0 .0208−0.025. The group's center of activity in the radio is the galaxy NGC 3862, whose radio flux is an order of magnitude stronger than for the other members of the group. We present coordinates derived from the Palomar plate archive together with recessional velocities, and analyze other characteristics of the group's galaxies. The results of 1400 MHz observations of NGC 3862 with the RATAN-600 radio telescope are presented. These observations indicate that the galaxy's radio emission is variable. c � 2005 Pleiades Publishing, Inc.

Laser heating and surface evaporation

In the present study, laser heating of solid substrate and evaporation of the surface are considered. The numerical method is employed to predict the temperature field in the solid as well as in the vapor front. The absorption of incident laser beam by the evaporating front and by the solid is accommodated to account for the absorption process. It is found that temperature decays sharply across the solid–vapor interface due to the location of the laser power intensity, which moves with the interface towards the solid bulk as evaporation of the surface progresses. The recession velocity becomes high in the early evaporation stage and as the heating period progresses, recession velocity becomes almost steady. Consequently, the transient behavior of evaporation can be observed during the early evaporation period.

Star formation in close pairs selected from the Sloan Digital Sky Survey

The effect of galaxy interactions on star formation has been investigated using Data Release One of the Sloan Digital Sky Survey (SDSS). Both the imaging and spectroscopy data products have been used to construct a catalogue of nearest companions to a volume-limited (0.03 < z < 0.1) sample of galaxies drawn from the main galaxy sample of SDSS. Of the 13 973 galaxies in the volume-limited sample, we have identified 12 492 systems with companions at projected separations less than 300 kpc. Star formation rates for the volume-limited sample have been calculated from extinction and aperture corrected Hα luminosities and, where available, IRAS data. Specific star formation rates were calculated by estimating galaxy masses from z-band luminosities, and r-band concentration indices were used as an indicator of morphological class. The mean specific star formation rate is significantly enhanced for projected separations less than 30 kpc. For late-type galaxies, the correlation extends out to projected separations of 300 kpc and is most pronounced in actively star-forming systems. The specific star formation rate is observed to decrease with increasing recessional velocity difference, but the magnitude of this effect is small compared to that associated with the projected separation. We also observe a tight relationship between the concentration index and pair separation; the mean concentration index is largest for pairs with separations of approximately 75 kpc and declines rapidly for separations smaller than this. This is interpreted as being due to the presence of tidally triggered nuclear starbursts in close pairs. Further, we find no dependence of star formation enhancement on the morphological type or mass of the companion galaxy.

Oviiand OviiiAbsorption by Hot Gas in the Vicinity of the Galaxy

We searched for evidence of soft X-ray absorption by hot gas in the vicinity of the Galaxy in a small sample of 15 type I active galactic nuclei (AGNs) observed with the high resolution X-ray gratings on board Chandra. We find that around half of the sight lines in our sample exhibit absorption due to local H- or He-like oxygen (or both) at confidence levels ranging from >90% to >3 σ. Depending on the sight line, the absorption can be identified with hot gas in particular local structures, the Local Group (LG), or the putative local hot intergalactic medium (IGM). Several sight lines in our sample coincide with sight lines in a study of O VI absorption by local gas, so an assumption of collisional ionization equilibrium (CIE) allows us to constrain the temperature of the local hot gas. In the southern Galactic hemisphere, we identify absorption along the sight line to Fairall 9 with the Magellanic Stream, and this gas has 105.75 < T < 106.35 K if CIE applies. There may be a blend of O VII absorption features along the sight line toward Mrk 509. LG clouds along this sight line may interact with a hot Galactic corona or a low-density LG medium (or the IGM). The sight line to 3C 120 does not appear to be associated with either local structure or UV-absorbing gas and may correspond to the local hot IGM. Gas in the Magellanic Stream extension along the sight line to Ark 564 has T < 106.1 K if it is in CIE. We show that hot absorbing outflows apparently detected in the spectra of NGC 4051, PDS 456, and PG 1211+143 could actually correspond to absorption by hot, local gas since the outflow velocity from each of these AGNs coincides with the respective cosmological recession velocity of the AGN. Our work implies that apparent mildly relativistic outflows from some QSOs are more likely to correspond to signatures of local, hot gas.

ChandraandXMM‐NewtonObservations of the Double Cluster A1758

A1758 was classified by Abell as a single rich cluster of galaxies, but a ROSAT observation showed that this system consists of two distinct clusters (A1758N and A1758S) separated by approximately 8' (a projected separation of 2 Mpc in the rest frame of the clusters). Only a few galaxy redshifts have been published for these two clusters, but the redshift of the Fe lines in the Chandra and XMM-Newton spectra shows that the recessional velocities of A1758N and A1758S are within 2100 km s-1. Thus, these two clusters most likely form a gravitationally bound system, but our imaging and spectroscopic analyses of the X-ray data do not reveal any sign of interaction between the two clusters. The Chandra and XMM-Newton observations show that A1758N and A1758S are both undergoing major mergers. A1758N is in the late stages of a large impact parameter merger between two 7 keV clusters. The two remnant cores have a projected separation of 800 kpc. Based on the measured pressure jumps preceding the two cores, they are receding from one another at less than 1600 km s-1. The two cores are surrounded by hotter gas (kT = 9-12 keV) that was probably shock heated during the early stages of the merger. The gas entropy in the two remnant cores is comparable with the central entropy observed in dynamically relaxed clusters, indicating that the merger-induced shocks stalled as they tried to penetrate the high-pressure cores of the two merging systems. Each core also has a wake of low-entropy gas, indicating that this gas was ram pressure stripped without being strongly shocked. A1758S is undergoing a more symmetric (lower impact parameter) merger between two 5 keV clusters. The two remnant cores are nearly coincident as seen in projection on the sky. The two cores are surrounded by hotter gas (9-11 keV), which was probably shock heated during the merger. Based on the pressure jumps preceding the two cores, they must have a relative velocity of less than 1400 km s-1. Unlike A1758N, there is no evidence of wakes of low-entropy gas.

The photometric properties of isolated early-type galaxies

Isolated galaxies are important because they probe the lowest density regimes inhabited by galaxies. We define a sample of 36 nearby isolated early-type galaxies for further study. Our isolation criteria require them to have no comparable-mass neighbours within 2 B-band magnitudes, 0.67 Mpc in the plane of the sky and 700 km s -1 in recession velocity. New wide-field optical imaging of 10 isolated galaxies with the Anglo-Australian Telescope confirms their early-type morphology and relative isolation. We also present imaging of four galaxy groups as a control sample. The isolated galaxies are shown to be more gravitationally isolated than the group galaxies. We find that the isolated early-type galaxies have a mean effective colour of (B - R) e = 1.54 ± 0.14, similar to their high-density counterparts. They reveal a similar colour-magnitude relation slope and small intrinsic scatter to cluster ellipticals. They also follow the Kormendy relation of surface brightness versus size for luminous cluster galaxies. Such properties suggest that the isolated galaxies formed at a similar epoch to cluster galaxies, such that the bulk of their stars are very old. However, our galaxy modelling reveals evidence for dust lanes, plumes, shells, boxy and disc isophotes in four out of nine galaxies. Thus at least some isolated galaxies have experienced a recent merger/accretion event, which may have induced a small burst of star formation. We derive luminosity functions for the isolated galaxies and find a faint slope of -1.2, which is similar to the 'universal' slope found in a wide variety of environments. We examine the number density distribution of galaxies in the field of the isolated galaxies. Only the very faintest dwarf galaxies (M R ≥ -15.5) appear to be associated with the isolated galaxies, whereas any intermediate-luminosity galaxies appear to lie in the background. Finally, we discuss possible formation scenarios for isolated early-type galaxies. Early epoch formation and a merger/accretion of galaxies are possible explanations. The collapse of a large, virialized group is an unlikely explanation, but that of a poor group remains viable.