Decrease In Luminosity Research Articles

Ionised carbon and galaxy activity

We investigate the possibility that the decrease in the relative luminosity of the 158 μ m [C ii] line with the far-infrared luminosity in extragalactic sources stems from a stronger contribution from the heated dust emission in the more distant sources. Because these surveys are flux limited in nature, the luminosity of the detected objects increases with distance. However, the [C ii] luminosity does not climb as steeply as that of the far-infrared, giving the decline in the $L_{\rm [CII]}/L_{\rm FIR}$ ratio with L FIR . Investigating this further, we find that the [C ii] luminosity exhibits similar drops as measured against the carbon monoxide and radio continuum luminosities. The former may indicate that at higher luminosities a larger fraction of the carbon is locked up in the form of molecules and/or that the CO line radiation also contributes to the cooling, done mainly by the [C ii] line at low luminosities. The latter hints at increased activity in these galaxies at greater distances, so we suggest that, in addition to an underlying heating of the dust by a stellar population, there is also heating of the embedded dusty torus by the ultra-violet emission from the active nucleus, resulting in an excess in the far-infrared emission from the more luminous objects.

Infrared Galaxies in the Nearby Universe

We used the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) to study the morphological properties of 1137 nearby infrared (IR) galaxies, most of which are brighter than 15.9 mag in r-band. This sample was drawn from a cross-correlation of the Infra-Red Astronomical Satellite (IRAS) point source catalog redshift survey with DR5 at z 0.08. Based on this IR galaxy sample, we constructed five volume-limited sub-samples with IR luminosity ranging from 109.5L⊙ to 1012L⊙. By deriving the IR luminosity functions (LF) for different morphological types, we found that normal spiral galaxies are the dominant population below LIR~8×1010 L⊙; while the fraction of barred spiral galaxies increases with increasing IR luminosity and becomes dominant in spiral galaxies beyond LIR5×1010L⊙. As the IR luminosity decreases, the IR galaxies become more compact and have lower stellar masses. The analysis also shows that normal spiral galaxies give the dominant contribution to the total comoving IR energy density in the nearby universe, while, in contrast, the contribution from peculiar galaxies is only 39%.

Clustered star formation as a natural explanation for the Hα cut-off in disk galaxies

The rate of star formation in a galaxy is often determined by the observation of emission in the Halpha line, which is related to the presence of short-lived massive stars. Disk galaxies show a strong cut-off in Halpha radiation at a certain galactocentric distance, which has led to the conclusion that star formation is suppressed in the outer regions of disk galaxies. This is seemingly in contradiction to recent observations in the ultraviolet which imply that disk galaxies have star formation beyond the Halpha cut-off, and that the star-formation-rate surface density is linearly related to the underlying gas surface density, which is a shallower relationship than that derived from Halpha luminosities. In a galaxy-wide formulation, the clustered nature of star formation has recently led to the insight that the total galactic Halpha luminosity is nonlinearly related to the galaxy-wide star formation rate. Here we show that a local formulation of the concept of clustered star formation naturally leads to a steeper radial decrease in the Halpha surface luminosity than in the star-formation-rate surface density, in quantitative agreement with the observations, and that the observed Halpha cut-off arises naturally.

Spectral variability of GX 339−4 in a hard-to-soft state transition★

We report on INTEGRAL observations of the bright black hole transient GX 339−4 performed during the period 2004 August–September, including the fast transition (10 h) observed simultaneously with INTEGRAL and RXTE on August 15 and previously reported. Our data cover three different spectral states, namely hard/intermediate state (HIMS), soft/intermediate state (SIMS) and high/soft state (HSS). We investigate the spectral variability of the source across the different spectral states. The hard X-ray spectrum becomes softer during the HIMSto-SIMS transition, but it hardens when reaching the HSS. A principal component analysis demonstrates that most of the variability occurs through two independent modes: a pivoting of the spectrum around 6 keV (responsible for 75 per cent of the variance) and an intensity variation of the hard component (responsible for 21 per cent). The pivoting is interpreted as due to changes in the soft cooling photon flux entering the corona, the second mode as fluctuations of the heating rate in the corona. These results are very similar to those previously obtained for Cygnus X-1. Our spectral analysis of the spectra of GX 339−4 shows a high energy excess with respect to pure thermal Comptonization models in the HIMS: a non-thermal power-law component seems to be requested by data. In all spectral states joint IBIS, SPI and JEM-X data are well represented by hybrid thermal/non-thermal Comptonization (EQPAIR). These fits allow us to track the evolution of each spectral component during the spectral transition. The spectral evolution seems to be predominantly driven by a reduction of the ratio of the electron heating rate to the soft cooling photon flux in the corona, lh/ls. The inferred accretion disc soft thermal emission increases by about two orders of magnitude, while the Comptonized luminosity decreases by at most a factor of 3. This confirms that the softening we observed is due to a major increase in the flux of soft cooling photons in the corona associated with a modest reduction of the electron heating rate.

Probing Shock Breakout with Serendipitous GALEX Detections of Two SNLS Type II-P Supernovae

We report the serendipitous detection by GALEX of fast (<1 day) rising (≳1 mag) UV emission from two Type II plateau (II-P) supernovae (SNe) at z = 0.185 and 0.324 discovered by the Supernova Legacy Survey. Optical photometry and VLT spectroscopy 2 weeks after the GALEX detections link the onset of UV emission to the time of shock breakout. Using radiation hydrodynamics and non-LTE radiative transfer simulations, and starting from a standard red supergiant (RSG; Type II-P SN progenitor) star evolved self-consistently from the main sequence to iron core collapse, we model the shock breakout phase and the 55 hr that follow. The small scale height of our RSG atmosphere model suggests that the breakout signature is a thermal soft X-ray burst (λpeak ~ 90 A) with a peak duration of ≾2000 s. Longer durations are possible but require either an extended and tenuous nonstandard envelope or an unusually dense RSG wind with M ~ 10^(-3)M_☉yr^(-1). The GALEX observations miss the peak of the luminous (M_(FUV)≈ − 20), UV burst but unambiguously capture the rise of the emission and a subsequent 2 day long plateau. The postbreakout, UV-bright plateau is a prediction of our model in which the shift of the peak of the spectral energy distribution (SED) from ∼100 to ∼1000 A and the ejecta expansion both counteract the decrease in bolometric luminosity from ∼10^(11) to ~ 10^9 L_☉ over that period. Based on the observed detection efficiency of our study, we make predictions for the breakout detection rate of the GALEX Time Domain Survey.

Measuring the Fraction of Obscured Quasars by the Infrared Luminosity of Unobscured Quasars

Recent work has suggested that the fraction of obscured AGNs declines with increasing luminosity, but it has been difficult to quantify this trend. Here we attempt to measure this fraction as a function of luminosity by studying the ratio of mid-infrared to intrinsic nuclear bolometric luminosity in unobscured AGNs. Because the mid-infrared is created by dust reprocessing of shorter wavelength nuclear light, this ratio is a diagnostic of -->fobsc, the fraction of solid angle around the nucleus covered by obscuring matter. In order to eliminate possible redshift dependences while also achieving a large dynamic range in luminosity, we have collected archival 24 μm MIPS photometry from objects with -->z ~ 1 in the Sloan Digital Sky Survey, the Great Observatories Origins Deep Survey, and the Cosmic Evolution Survey. To measure the bolometric luminosity for each object, we used archival optical data supplemented by GALEX data. We find that the mean ratio of 24 μm to bolometric luminosity decreases by a factor of ~3 in the -->Lbol = 1044–3 × 1047 ergs s -->−1 range, but there is also a large scatter at constant -->Lbol. Using radiation transfer solutions for model geometries, we show how the IR/bolometric ratio relates to -->fobsc and compare these values with those obtained from samples of X-ray-selected AGNs. Although we find approximate agreement, our method indicates somewhat higher values of -->fobsc, particularly in the middle range of luminosities, suggesting that there may be a significant number of heavily obscured AGNs missed by X-ray surveys.

Convection during the Late Stages of Simmering in Type Ia Supernovae

Following unstable ignition of carbon, but prior to explosion, a white dwarf (WD) in a Type Ia supernova (SN Ia) undergoes a simmering phase. During this time, a central convective region grows and encompasses ~1 Msun of the WD over a timescale of ~1000 yrs, which sets the thermal and turbulent profile for the subsequent explosion. We study this time-dependent convection and summarize some of the key features that differ from the traditional, steady-state case. We show that the long conductive timescale above the convective zone and the extraction of energy to heat the WD core leads to a decrease of the convective luminosity and characteristic velocities near the convective zone's top boundary. In addition, differences in the composition between the convective core and the conductive exterior will significantly alter the location of this boundary. In this respect, we find the biggest effect due to complete 22Ne sedimentation prior to carbon ignition. These effects add diversity to the possible WD models, which may alter the properties of the SN Ia explosion.

Orientation Effects in Bipolar Planetary Nebulae

We show that the inclination to the line of sight of bipolar planetary nebulae strongly affects some of their observed properties. We model these objects as having a dusty equatorial density enhancement that produces extinction that varies with the viewing angle. Our sample of 29 nebulae taken from the literature shows a clear correlation between the inclination angle and the near-infrared and optical photometric properties as well as the detected luminosity of the objects. As the inclination angle increases (the viewing angle is closer to the equatorial plane) the objects become redder, their apparent luminosity decreases, and their projected expansion velocity becomes smaller. We compute two-dimensional models of stars embedded in dusty disklike structures of various shapes and compositions and show that the observed data can be reproduced by disk-star combinations with reasonable parameters. To compare with the observational data, we generate sets of model data by randomly varying the star and disklike structure parameters within a physically meaningful range. We conclude that a only a smooth pole to equator density gradient agrees with the observed phenomena.

A simplified model of jet power from active galactic nuclei

Aims. A simplified model of jet power from active galactic nuclei is proposed in which the relationship between jet power and disk luminosity is discussed by combining disk accretion with two mechanisms of extracting energy magnetically from a black hole accretion disk, i.e., the Blandford-Payne (BP) and the Blandford-Znajek (BZ) processes. Methods. By including the BP process into the conservation laws of mass, angular momentum and energy, we derive the expressions of the BP power and disk luminosity, and the jet power is regarded as the sum of the BZ and BP powers. Results. We find that the disk radiation flux and luminosity decrease because a fraction of the accretion energy is channelled into the outflow/jet in the BP process. It is found that the dominant cooling mode of the accretion disk is determined mainly by how the poloidal magnetic field decreases with the cylindrical radius of the jet. By using the parameter space we found, which consists of the black hole spin and the self-similar index of the configuration of the poloidal magnetic field frozen in the disk, we were able to compare the relative importance of the following quantities related to the jet production: (1) the BP power versus the disk luminosity, (2) the BP power versus the BZ power, and (3) the jet power versus the disk luminosity. In addition, we fit the jet power and broad-line region luminosity of 11 flat-spectrum radio quasars (FSRQs) and 17 steep-spectrum radio quasars (SSRQs) based on our model.

HIGH ENERGY SIGNATURES OF POST ADIABATIC SUPERNOVA REMNANTS

Between the well-known adiabatic and radiative stages of the Supernova remnant (SNR) evolution there is, in fact, a transition stage with a duration comparable to the duration of adiabatic one. Physical existence of the transition stage is motivated by cooling of some part of the downstream hot gas with formation of a thin cold shell that is joined to a shell of swept up interstellar medium (ISM). We give an approximate analytical method for full hydrodynamical description of the transition stage. On its base we investigate the evolution of X-ray and γ-ray radiation during this stage. It is shown that formation of a dense shell during the transition stage is accompanied by the decrease of X-ray luminosity because of hot gas cooling and increase of gamma-ray flux according to the increase of target proton density and CR energy in the newly born shell. The role of nonuniformity of ISM and its influence on the high energy fluxes from the SNRs is also discussed.

The evolution of the near-infrared galaxy luminosity function and colour bimodality up to z ≃ 2 from the UKIDSS Ultra Deep Survey Early Data Release

We present new results on the cosmological evolution of the near-infrared (near-IR) galaxy luminosity function (LF), derived from the analysis of a new sample of ∼22 000 KAB≤ 22.5 galaxies selected over an area of 0.6 deg2 from the Early Data Release of the UKIDSS Ultra Deep Survey (UDS). Our study has exploited the multiwavelength coverage of the UDS field provided by the new UKIDSS WFCAM K- and J-band imaging, the Subaru/XMM–Newton Deep Survey and the Spitzer Wide-Area Infrared Extragalactic survey. The unique combination of large area and depth provided by this new survey minimizes the complicating effect of cosmic variance and has allowed us, for the first time, to trace the evolution of the brightest sources out to z≃ 2 with good statistical accuracy. In agreement with previous studies, we find that the characteristic luminosity of the near-IR LF brightens by ≃1 mag between z= 0 and z≃ 2, while the total density decreases by a factor of ≃2. Using the rest-frame (U−B) colour to split the sample into red and blue galaxies, we confirm the classic luminosity-dependent colour bimodality at z≲ 1. However, the strength of the colour bimodality is found to be a decreasing function of redshift, and seems to disappear by z≳ 1.5. Due to the large size of our sample, we are able to investigate the differing cosmological evolution of the red and blue galaxy populations. It is found that the space density of the brightest red galaxies (MK≤− 23) stays approximately constant with redshift, and that these sources dominate the bright end of the LF at redshifts z≲ 1. In contrast, the brightening of the characteristic luminosity and mild decrease in space density displayed by the blue galaxy population leads them to dominate the bright end of the LF at redshifts

Spectral Evolution of NGC 1313 X-2: Evidence against the Cool Disk Model

The presence of a cool multicolor disk component with an inner disk temperature kT=0.1~0.3 keV at a luminosity L>10^40 erg/s has been interpreted as evidence that the ultraluminous X-ray source NGC 1313 X-2 harbors an intermediate-mass black hole (IMBH). The temperature of a disk component should vary with luminosity as $L\propto T^4$. However, upon investigating the spectral evolution with multiple XMM-Newton observations, we found that the cool disk component failed to follow this relation with a confidence level of 0.999964. Indeed, the luminosity decreases as the temperature increases, and the luminosities at high temperatures are more than an order of magnitude less than expected from the $L\propto T^4$ extrapolation of luminosities at low temperatures. This places a strong constraint against the validity of modeling the X-ray spectra of NGC 1313 X-2 as emission from the accretion disk of an IMBH. The decrease in luminosity with increasing temperature of the soft component follows the trend suggested by a model in which the soft emission arises from an outflow from a stellar-mass black hole with super-Eddington accretion viewed along the symmetry axis. Alternatively, the spectra can be adequately fitted by a p-free disk model with kT=~2 keV and p=~0.5. The spectral evolution is consistent with the $L\propto T^4$ relation and appears to be a high luminosity extension of the L-kT relation of Galactic black holes. This, again, would suggest that the emission is from a super-Eddington accreting stellar mass black hole.

Structure of the accretion disk in the cataclysmic variable UX UMa in the transition to its quiescent state

Our analysis of BV RI light curves for the cataclysmic variable UX UMa obtained in intermediate activity states, in the transition between the active and quiescent states of the system on March 12, 1997 and May 3, 2000, shows that the shapes of these light curves cannot be adequately described using the standard hot-spot model. A model with a “hot line” near the edge of the disk and a two-armed spiral structure on the disk surface reproduces much better out-of-eclipse variations in the light curves. The presence of an extended hot line can explain the anomalous shape of the I light curve on March 12, 1997. The decrease in the observed luminosity of the system between March 12, 1997 and May 3, 2000 could be due to a decrease in the disk luminosity by a factor of 2–2.5; the higher disk luminosity on the earlier date is associated with appreciable deviations of the radial temperature distribution of the disk material from that for the standard model. The phases and depths of dips in the out-of-eclipse sections of the UX UMa light curves are due primarily to the parameters of the complex shape of the accretion disk, which has a spiral structure located mainly near its outer edge. The contribution of the spiral arms in the V filter reaches 20–50% of the total disk radiation. The crest of the first spiral wave in our model maintains its approximate position in azimuth; this structure could represent a bulge in a halo at the outer edge of the disk near orbital phases φ ∼ 0.7, in the direction of the continuation of the extended shock in the disk itself. The position of the crest of the second spiral arm changes with time. This structure may represent a one-armed spiral wave near the apastron of the weakly elliptical disk. Finally, the observations testify to the presence of another spiral arm that is les clearly manifest in terms of both its luminosity and its height above the unperturbed disk surface. Thus, in an intermediate activity state of UX UMa, the surface of the accretion disk is distorted by the action of a two-armed spiral structure in the outer regions of the disk, which is asymmetric in both its luminosity and dimensions, and a bulge at the disk edge in the region of its interaction with the inflow to the disk.

Photometric Stellar Variability in the Galactic Center

We report the results of a diffraction-limited, photometric variability study of the central 5'' × 5'' of the Galaxy conducted over the past 10 years using speckle imaging techniques on the W. M. Keck I 10 m telescope. Within our limiting magnitude of mK < 16 mag for images made from a single night of data, we find a minimum of 15 K[2.2 μm]-band variable stars out of 131 monitored stars. The only periodic source in our sample is the previously identified variable IRS 16SW, for which we measure an orbital period of 19.448 ± 0.002 days. In contrast to recent results, our data on IRS 16SW show an asymmetric phased light curve with a much steeper fall time than rise time, which may be due to tidal deformations caused by the proximity of the stars in their orbits. We also identify a possible wind colliding binary (IRS 29N) based on its photometric variation over a few year timescale, which is likely due to episodic dust production. None of the four luminous blue variable (LBV) candidates in our sample show the characteristic large increase or decrease in luminosity. However, our time baseline is too short to rule them out as LBVs. Among the remaining variable stars, the majority are early-type stars, and three are possibly variable due to line-of-sight extinction variations. For the seven OB stars at the center of our field of view that have well-determined three-dimensional orbits, we see no evidence of flares or dimming of their light, which limits the possibility of a cold, geometrically thin, inactive accretion disk around the supermassive black hole, Sgr A*.

Photometric Stellar Variability in the Galactic Center

We report the results of a diffraction-limited, photometric variability study of the central 5′′ × 5′′ of the Galaxy conducted over the past 10 years using speckle imaging techniques on the W.M. Keck I 10 m telescope. Within our limiting magnitude of mK < 16 for maps made from a single night of data, we find a minimum of 25 variable stars out of 131 monitored stars. Among 46 stars brighter than mK < 14 which have roughly uniform photometric uncertainties, there are 16 variable stars. This suggests a minimum variable star frequency of 34%. We see no evidence of fares or dimming of the 7 stars that have known 3-dimensional orbits in our study, which greatly limits the possibility of a cold, geometrically-thin, inactive accretion disk around the supermassive black hole, Sgr A*. While large populations of binaries have been posited to exist in this region both to explain the presence of young stars in the vicinity of a black hole and because of the high stellar densities, only one eclipsing binary is identiffed. The only periodic source in our sample is the previously identiffed variable IRS 16SW (P = 19.448 ± 0.002 days). In contrast to recent results, our data show an asymmetric phased light curve with a much steeper fall-time than rise-time. IRS 29N shows variability on time scales of ≈ 5 years and has a known spectral type of WC9. This variation is likely due to episodic dust production, which may suggest that this source is a binary star system. Only 2 of the LBV candidates in our sample (16NW, 16SW) show variability and none of the 4 show the characteristic large increase or decrease in luminosity. However, our time baseline is too short to rule them out as LBVs. Our study has shown that photometric variability provides a useful handle on the unusual massive star population surrounding our Galaxy's supermassive black hole and its local environment.

The Long‐Term Behavior of the Semiregular M Supergiant Variable BC Cygni

ABSTRACTThe long‐term brightness changes in the M supergiant, type C semiregular variable, Type II supernova progenitor BC Cyg from 1890 to the present are examined using archival data obtained from photographic plates in the collections of Harvard College Observatory and Sternberg Astronomical Institute, in conjunction with AAVSO observations. BC Cyg pulsates with a period close to 700 days but underwent a 0.5 mag increase in brightness between 1900 and 2000, in conjunction with a decrease in pulsation period from 699 to 687 days. Such changes appear to be evolutionary in origin, representing a small contraction of the star associated with a slight decrease in luminosity. Its evolutionary mass is estimated to be ∼19 M⊙ from its membership in Berkeley 87, a feature that also permits it to be used to test the M supergiant period‐luminosity relation.

The AGN-obscuring Torus: The End of the "Doughnut" Paradigm?

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central engine. The compact sizes (only a few pc) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black-hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined from detailed modeling of the IR emission from clumpy tori. We find that torus clouds were likely detected in recent water maser observations of NGC 3079. In the wind scenario, the AGN main dynamic channel for release of accreted mass seems to be switching at low luminosities from torus outflow to radio jets. The torus disappears when the bolometric luminosity decreases below about \E{42} erg/sec because the accretion onto the central black hole can no longer sustain the required cloud outflow rate. This disappearance seems to have been observed in both LINERs and radio galaxies. With further luminosity decrease, suppression of cloud outflow spreads radially inward from the disk's dusty, molecular region into its atomic, ionized zone, resulting in disappearance of the broad emission line region at lower luminosities, yet to be determined.

질량비가 작은 접촉쌍성 HN UMa와 II UMa - III

BVRI CCD 측광 관측에 의하여 질량비가 작은 접촉쌍성 HN UMa와 II UMa의 새로운 광도곡선을 얻었다. 새로운 광도곡선과 이미 발표된 분광관측으로부터 Wilson-Devinney 프로그램을 이용하여 이 두 별의 궤도요소와 절대 물리량을 얻었다. HN UMa와 II UMa를 포함한 절대물리량이 잘 알려진 21개의 질량비가 작은 접촉쌍성들의 진화 상태를 조사하였다. 그 결과 질랑비가 작은 접촉쌍성의 반성은 영년주계열 아래 놓이며, 이러한 현상은 질량이 작은 접촉쌍성의 반성에서의 질량손실을 가정할 경우, 비록 작의 양의 질량이지만 반성에서의 질량 감소는 상대적으로 광도의 감소가 현저히 작아지기 때문일 것으로 예상된다. We present newly observed BVRI CCD light curves for low mass ratio contact binaries, HN UMa and II UMa. The absolute dimensions of these objects were obtained by applying the Wilson-Devinney program to previously published spectroscopic analysis and to our observed photometric data. The evolutionary status of all 21 low mass ratio contact binary system including HN UMa and II UMa was then considered. The secondaries of all low mass ratio contact binaries are located below the zero age main sequence in HR diagram. This phenomenon could be explained by mass loss from the secondary component in the low mass contact binary system because even small mass loss affects luminosity decrease in the low mass stars.

Global auroral response to negative pressure impulses

It is well known that sharp increases/decreases in the solar wind dynamic pressure can result in sudden compression/decompression of the magnetosphere and subsequent magnetic positive/negative impulses (SI+/SI−) detected on the ground magnetometers. While the large‐scale enhancement of aurora during an SI+ has been well established, the response of aurora to an SI− is still little known. This prompts an interesting question whether the response of the global aurora to an SI− mirrors the response to an SI+. This letter reports results from a study of auroral images, acquired from the ultraviolet imager (UVI) on board the Polar satellite, during 13 SI− events. It is found that, in most cases, the luminosity of the aurora indeed showed a clear decrease almost immediately after the decompression. In some cases, the luminosity decrease exhibits a day‐to‐night fading effect and is consistent with the tailward propagation of the magnetosphere decompression front. Auroral particle observations from DMSP indicate that reduction of CPS electron precipitation is the major cause of the large‐scale auroral dimming. We propose that an induction electric field triggered by the sudden expansion of the magnetosphere at the expansion front along with adiabatic decompression and magnetic reconfiguration are responsible for the observed effect.

Photometric Observations of Southern Abell Cluster Redshifts Survey Clusters: Structure of Galaxies in the Inner Region of Clusters of Galaxies

We analyze photometric properties of 1384 cluster galaxies as a function of the normalized distance to cluster center. These galaxies were selected in the central region ($r/r_{200} \leq$ 0.8) of 14 southern Abell clusters chosen from the Southern Abell Cluster Redshifts Survey (SARS). For 507 of these galaxies we also obtained their luminosity profiles. We have studied the morphology-clustercentric distance relation on the basis of the shape parameter $n$ of the S\'ersic's law. We also have analyzed the presence of a possible segregation in magnitude for both, the galaxy total luminosity and that of their components (i.e. the bulge and the disk). Results show a marginal ($2\sigma$ level) decrease of the total luminosity as a function of normalized radius. However, when bulges are analyzed separately, a significant luminosity segregation is found ($3\sigma$ and $2\sigma$ for galaxies in projection and member galaxies respectively). The fraction of bulges brighter than $M_B \leq -22$ is three times larger in the core of clusters than in the outer region. Our analysis of the disk component suggests that disks are, on average, less luminous in the cluster core than at $r/r_{200} \sim 0.8$. In addition, we found that the magnitude-size relation as a function of $r/r_{200}$ indicates (at $2\sigma$ level) that disks are smaller and centrally brighter in the core of clusters. However, the Kormendy relation (the bulge magnitude-size relation) appears to be independent of environment.