Radial Light Profiles Research Articles

Rest-frame Near-infrared Radial Light Profiles up to z = 3 from JWST/NIRCam: Wavelength Dependence of the Sérsic Index

We examine the wavelength dependence of radial light profiles based on Sérsic index n measurements of 1067 galaxies with M * ≥ 109.5 M ⊙ and in the redshift range 0.5 < z < 3. The sample and rest-frame optical light profiles are drawn from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and 3D Hubble Space Telescope (HST); rest-frame near-infrared light profiles are inferred from images collected for the Cosmic Evolution Early Release Science (CEERS) program with the Near Infrared Camera (NIRCam) on board of the James Webb Space Telescope (JWST). n shows only a weak dependence on the wavelength, regardless of the redshift, galaxy mass, and type. On average, star-forming galaxies have n = 1–1.5 and quiescent galaxies have n = 3–4 in the rest-frame optical and near-infrared. The strong correlation at all wavelengths between n and star formation activity implies a physical connection between the radial stellar mass profile and star formation activity. The main caveat is that the current sample is too small to discern trends for the most massive galaxies (M * > 1011 M ⊙).

Formation of the largest galactic cores through binary scouring and gravitational wave recoil

ABSTRACT Massive elliptical galaxies are typically observed to have central cores in their projected radial light profiles. Such cores have long been thought to form through ‘binary scouring’ as supermassive black holes (SMBHs), brought in through mergers, form a hard binary and eject stars from the galactic centre. However, the most massive cores, like the $\sim 3{\, \mathrm{kpc}}$ core in A2261-BCG, remain challenging to explain in this way. In this paper, we run a suite of dry galaxy merger simulations to explore three different scenarios for central core formation in massive elliptical galaxies: ‘binary scouring’, ‘tidal deposition’, and ‘gravitational wave (GW) induced recoil’. Using the griffin code, we self-consistently model the stars, dark matter, and SMBHs in our merging galaxies, following the SMBH dynamics through to the formation of a hard binary. We find that we can only explain the large surface brightness core of A2261-BCG with a combination of a major merger that produces a small $\sim 1{\, \mathrm{kpc}}$ core through binary scouring, followed by the subsequent GW recoil of its SMBH that acts to grow the core size. Key predictions of this scenario are an offset SMBH surrounded by a compact cluster of bound stars and a non-divergent central density profile. We show that the bright ‘knots’ observed in the core region of A2261-BCG are best explained as stalled perturbers resulting from minor mergers, though the brightest may also represent ejected SMBHs surrounded by a stellar cloak of bound stars.

The Diffuse Light Envelope of Luminous Red Galaxies

Abstract We use a stacking method to study the radial light profiles of luminous red galaxies (LRGs) at redshift ∼0.62 and ∼0.25, out to a radial range of 200 kpc. We do not find noticeable evolution of the profiles at the two redshifts. The LRG profiles appear to be well approximated by a single Sérsic profile, although some excess light can be seen outside 60 kpc. We quantify the excess light by measuring the integrated flux and find that the excess is about 10%—a non-dominant but still nonnegligible component.

THE MASS PROFILE AND SHAPE OF BARS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): SEARCH FOR AN AGE INDICATOR FOR BARS

We have measured the radial light profiles and global shapes of bars using two-dimensional 3.6 $\mu m $ image decompositions for 144 face-on barred galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). The bar surface brightness profile is correlated with the stellar mass and bulge-to-total (B/T) ratio of their host galaxies. Bars in massive and bulge-dominated galaxies (B/T$>$0.2) show a flat profile, while bars in less massive, disk-dominated galaxies (B/T$\sim$0) show an exponential, disk-like profile with a wider spread in the radial profile than in the bulge-dominated galaxies. The global two-dimensional shapes of bars, however, are rectangular/boxy, independent of the bulge or disk properties. We speculate that because bars are formed out of disk, bars initially have an exponential (disk-like) profile which evolves over time, trapping more stars into the boxy bar orbits. This leads bars to become stronger and have flatter profiles. The narrow spread of bar radial profiles in more massive disks suggests that these bars formed earlier (z$>$1), while the disk-like profiles and a larger spread in the radial profile in less massive systems imply a later and more gradual evolution, consistent with the cosmological evolution of bars inferred from observational studies. Therefore, we expect that the flatness of the bar profile can be used as a dynamical age indicator of the bar to measure the time elapsed since the bar formation. We argue that cosmic gas accretion is required to explain our results on bar profile and the presence of gas within the bar region.

GALFIT-CORSAIR: Implementing the Core-Sérsic Model Into GALFIT

We introduce GALFIT-CORSAIR: a publicly available, fully retro-compatible modification of the two-dimensional (2D) fitting software GALFIT (ver. 3), which adds an implementation of the core-Sérsic model. We demonstrate the software by fitting the images of NGC 5557 and NGC 5813, which have been previously identified as core-Sérsic galaxies by their one-dimensional radial light profiles. These two examples are representative of different dust obscuration conditions, and of bulge/disk decomposition. To perform the analysis, we obtained deep Hubble Legacy Archive (HLA) mosaics in the F555W filter (∼V band). We successfully reproduce the results of the previous one-dimensional analysis, modulo the intrinsic differences between the one-dimensional and the 2D fitting procedures. The code and the analysis procedure described here have been developed for the first coherent 2D analysis of a sample of core-Sérsic galaxies, which will be presented in a forthcoming paper. As the 2D analysis provides better constraining on multicomponent fitting, and is fully seeing-corrected, it will yield complementary constraints on the missing mass in depleted galaxy cores.

Search for galaxy‐ICM interaction in rich clusters of galaxies

AbstractBased on optical and X‐ray data for a sample of 34 relaxed rich clusters with redshift of 0.1–0.9, we studied the relative spatial distribution of the two major baryon contents, the cluster galaxies and the hot plasmas. Using photometric data taken with the UH88 telescope, we determined the integrated radial light profiles of member galaxies in each cluster using two independent approaches, i.e., the field background subtraction and the color‐magnitude filtering. The ICM mass profile of each cluster in our sample was derived from a spatially‐resolved spectral analysis using XMM‐Newton and Chandra data. When the sample is divided into three subsamples with redshift intervals of z = 0.11–0.22, 0.22–0.45, and 0.45– 0.89, the galaxy light vs. ICM mass ratio profiles for the central 0.65R500 regions were found to steepen from the higher‐ to lower‐ redshift subsamples, meaning that the galaxies become more concentrated in the ICM sphere towards lower redshifts. Besides, the galaxy light vs. total mass ratio profiles also exhibit gradual concentration towards lower redshift. We interpret that the galaxies, the ICM, and the dark matter components followed a similar spatial distribution in the early phase (z &gt; 0.5), while the galaxies have fallen towards the center relative to the ICM and dark matter. Such galaxy infall is likely tobe caused by ICM drag when galaxies move through the ICM, even though the dynamical friction can enhance the infall of the most massive galaxies. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

PROBING OF THE INTERACTIONS BETWEEN THE HOT PLASMAS AND GALAXIES IN CLUSTERS FROMz= 0.1 TO 0.9

Based on optical and X-ray data for a sample of 34 relaxed rich clusters of galaxies with redshifts of 0.1-0.9, we studied relative spatial distributions of the two major baryon contents, the cluster galaxies and the hot plasmas. Using multi-band photometric data taken with the UH88 telescope, we determined the integrated (two dimensional) radial light profiles of member galaxies in each cluster using two independent approaches, i.e., the background subtraction and the color-magnitude filtering. The ICM mass profile of each cluster in our sample, also integrated in two dimensions, was derived from a spatially-resolved spectral analysis using XMM-Newton and Chandra data. Then, the radially-integrated light profile of each cluster was divided by its ICM mass profile, to obtain a profile of "galaxy light vs. ICM mass ratio". The ratio profiles over the central 0.65 R500 regions were found to steepen from the higher- to lower- redshift subsamples, meaning that the galaxies become more concentrated in the ICM sphere towards lower redshifts. The evolution is also seen in galaxy number vs. ICM mass ratio profiles. A range of systematic uncertainties in the galaxy light measurements, as well as many radius-/redshift- dependent biases to the galaxy vs. ICM profiles have been assessed, but none of them is significant against the observed evolution. Besides, the galaxy light vs. total mass ratio profiles also exhibit gradual concentration towards lower redshift. We interpret in the context that the galaxies, the ICM, and the dark matter components followed a similar spatial distribution in the early phase (z>0.5), while the galaxies have fallen towards the center relative to the others at a later phase.

Parametrizing arbitrary galaxy morphologies: potentials and pitfalls

We demonstrate that morphological observables (e.g. steepness of the radial light profile, ellipticity, asymmetry) are intertwined and cannot be measured independently of each other. We present strong arguments in favour of model-based parametrisation schemes, namely reliability assessment, disentanglement of morphological observables, and PSF modelling. Furthermore, we demonstrate that estimates of the concentration and Sersic index obtained from the Zurich Structure & Morphology catalogue are in excellent agreement with theoretical predictions. We also demonstrate that the incautious use of the concentration index for classification purposes can cause a severe loss of the discriminative information contained in a given data sample. Moreover, we show that, for poorly resolved galaxies, concentration index and M_20 suffer from strong discontinuities, i.e. similar morphologies are not necessarily mapped to neighbouring points in the parameter space. This limits the reliability of these parameters for classification purposes. Two-dimensional Sersic profiles accounting for centroid and ellipticity are identified as the currently most reliable parametrisation scheme in the regime of intermediate signal-to-noise ratios and resolutions, where asymmetries and substructures do not play an important role. We argue that basis functions provide good parametrisation schemes in the regimes of high signal-to-noise ratios and resolutions. Concerning Sersic profiles, we show that scale radii cannot be compared directly for profiles of different Sersic indices. Furthermore, we show that parameter spaces are typically highly nonlinear. This implies that significant caution is required when distance-based classificaton methods are used.

A New Technique for Galaxy Photometric Redshifts in the Sloan Digital Sky Survey

Traditional photometric redshift methods use only color information about the objects in question to estimate their redshifts. This paper introduces a new method utilizing colors, luminosity, surface brightness, and radial light profile to measure the redshifts of galaxies in the Sloan Digital Sky Survey (SDSS). We take a statistical approach: distributions of galaxies from the SDSS Large-Scale Structure (LSS; spectroscopic) sample are constructed at a range of redshifts, and target galaxies are compared to these distributions. An adaptive mesh is implemented to increase the percentage of the parameter space populated by the LSS galaxies. We test the method on a subset of galaxies from the LSS sample, yielding rms Delta-z of 0.025 for red galaxies and 0.030 for blue galaxies (all with z < 0.25). Possible future improvements to this promising technique are described, as is our ongoing work to extend the method to galaxies at higher redshift.

Broadband Imaging of a Large Sample of Irregular Galaxies

We present the results of UBV imaging of a large sample of irregular galaxies: 94 Im systems, 24 blue compact dwarfs (BCDs), and 18 Sm galaxies. We also include JHK imaging of 42 of these galaxies. The sample spans a large range in galactic parameters. Ellipse fit axial ratios, inclinations, and position angles are derived, integrated photometry and azimuthally averaged surface photometry profiles are determined, and exponential fits give the central surface brightnesses, scale lengths, and isophotal and half-power radii. These data are used to address the shapes of Im galaxies, look for clues to past interactions in large-scale peculiarities, examine the nature and consequences of bars, study color gradients and large-scale color variations, and compare the exponential disk profiles of the young and old stellar components. For example, color gradients exhibit a great variety and not all passbands are correlated. Bars are associated with higher star formation rates. Many irregulars show a double-exponential radial light profile that is steeper in the outer parts, and these are reproduced by a new model of star formation that is discussed in a companion paper. Some galaxies, primarily BCDs, have double exponentials that are steeper (and bluer) in the inner parts, presumably from centralized star formation. Im-type galaxies have thicker, less prominent dust layers than spiral galaxies because of their lower average surface densities and midplane extinctions.

The structure of elliptical galaxies in the Virgo cluster. Results from the INT Wide Field Survey

We report on a complete CCD imaging survey of 226 elliptical galaxies in the North-East quadrant of the Virgo cluster, representative of the properties of giant and dwarf elliptical galaxies in this cluster. We fit their radial light profiles with the Sersic model of light distribution. We confirm the result of Graham & Guzman ([CITE], AJ, 125, 2936) that the apparent dichotomy between E and dE galaxies in the luminosity– plane no longer appears when other structural parameters are considered and can be entirely attributed to the onset of “core” galaxies at mag. When “core” galaxies are not considered, E and dE form a unique family with n linearly increasing with the luminosity. For 90 galaxies we analyze the color indices, both in the nuclear and in the outer regions. Both indices are bluer toward fainter luminosities. We find also that the outer color gradients do not show any significant correlation with the luminosity. The scatter in all color indicators increases significantly toward lower luminosities, e.g. galaxies fainter than have a spread > 0.5 mag.

Structural properties of discs and bulges of early-type galaxies

We have used the EFAR sample of galaxies to study the light distributions of early-type galaxies. We decompose the 2D light distribution of the galaxies in a flattened spheroidal component with a Sersic radial light profile and an inclined disc component with an exponential light profile. We show that the brightest, bulge dominated elliptical galaxies have a fairly broad distribution in the Sersic profile shape parameter n_B, with a median of about 3.7 and a sigma of ~0.9. Other galaxies have smaller n_B values, meaning that spheroids are in general less concentrated than the n_B=4 de Vaucouleurs-law profile. The results of our light decompositions are robust, even though without kinematic information we cannot prove that the spheroids and discs are really pressure- and rotation-supported stellar systems. If we assume that the detected spheroids and discs are indeed separate components, we can draw the following conclusions: 1) the spheroid and disc scale sizes are correlated; 2) bulge-to-total luminosity ratios, bulge effective radii, and bulge n_B values are all positively correlated; 3) the bivariate space density distribution of elliptical galaxies in the (luminosity, scale size)-plane is well described by a Schechter luminosity function in and a log-normal scale-size distribution at a given luminosity; 4) at the brightest luminosities, the scale size distribution of elliptical galaxies is similar to those of bright spiral galaxies; at fainter luminosities the elliptical scale size distribution peaks at distinctly smaller sizes than the spiral galaxy distribution; and 5) bulge components of early-type galaxies are typically a factor 1.5 to 2.5 smaller than the disks of spiral galaxies, while disc components of early-type galaxies are typically twice as large as the discs of spiral galaxies. [abridged]

Introducing GOLDMine: A new galaxy database on the WEB

The new World Wide Web site (Galaxy On Line Database Milano Network) (http:// goldmine.mib.infn.it) contains a multiwavelength data-base of an optically selected sample of 3267 galaxies in the Virgo cluster and in the Coma Supercluster. It is designed for professional astronomers who wish to find data and images for these galaxies. Data gathered in 15 years of observational campaigns by the authors or taken from the literature include general parameters (catalogue names, celestial coordinates, morphological type, recessional velocity etc.), multiwavelength continuum photometry (total UV, U, B, V, J, H, K, FIR and radio magnitudes/flux densities), line photometry (HI, H2 ,H ), dynamical parameters (rotational velocity from the HI and H lines, velocity dispersion) and structural parameters (light concentration index, eective radius and brightness, asymptotic magnitude) in the optical (B and V) and Near Infrared (H or K) bands. Images include finding charts, optical (B and V), H, Near Infrared (H and/or K) and true color RGB frames (when available). Radial light profiles obtained from the B, V, H or K band images are also available. Integrated optical spectra along with broad Spectral Energy Distributions (SED) from the UV to the radio domain are given. All images can be obtained in JPG format, but the original (reduced) FITS images can be downloaded as well. The database will be updated regularly and will be extended to other local clusters and superclusters. Astronomers who wish to have their images included in GOLDMine are strongly encouraged to send us their material.

HST imaging of an old galaxy group at z=1.55

We present high-resolution imaging in the rest-frame optical of the weak radio source LBDS53W091 (Windhorst, van Heerde and Katgert: 1984, AA Spinrad et al.: 1997, ApJ 484, 581). We have obtained deep Hubble Space Telescope imaging over 10 orbits with NICMOS (Thompson et al.: 1998, ApJLett 492, 95), using camera 2 with the F160W H-band filter (l.6μm) which is a good approximation to the rest-frame R-band. Our observations reveal a radial light profile which is well fit by a de Vaucouleurs r 1/4 law, with a scale length of r e = 0.3″ (2.3h 70 −1 kpc for Ω M = 0.3 and ΩΛ = 0). The elliptical morphology of the radio galaxy indicates a dynamically-evolved old system (consistent with the spectroscopic results). Some surrounding objects lie on the color:magnitude relation for a cluster at z = 1.55, and are likely to be associated. The group of galaxies are somewhat more luminous than the fundamental plane of ellipticals (Djorgovski and Davis: 1987, ApJ 313, 59; Dressler et al.: 1987, ApJ 313, 42) at z = 0 subject to (1 + z)4 surface brightness dimming, but are consistent with estimates of the fundamental plane at high redshift subject to passive luminosity evolution from a formation epoch of z > 3 (e.g., van Dokkum et al.: 1998, ApJLett 504, 17).

Imaging of Ultraluminous Infrared Galaxies in the Near-Ultraviolet

We present the first ground-based U' (λcentral = 3410 A, Δλ = 320 A) images of ultraluminous infrared galaxies (ULIGs). Two samples were observed: (1) ULIGs with mid-infrared colors characteristic of active galactic nuclei (f25 μm/f60 μm > 0.2), which are believed to represent a critical transition phase between cooler ULIGs and optically selected QSOs according to a previously proposed evolutionary model, and (2) the complementary cool ULIGs (f25 μm/f60 μm < 0.2), which in the evolutionary model are the progenitors of warm ULIGs and which have many characteristics associated with active star formation. Although in some cases there is also emission identified with an active galactic nucleus, the U' emission originates primarily in massive young stars and as such allows a direct examination of the sites of recent high-mass star formation. Strong U' emission (median total MU = -20.8) is seen in all systems, and in some cases the extended tidal features (both the smooth stellar distribution and compact star-forming features) contribute up to 60%–80% of the total flux. The star-forming regions in both samples are found to have ages based on spectral synthesis models in the range 10–100 Myr, and most differences in color between them can be attributed to the effects of dust reddening. Additionally, it is found that star formation in compact knots in the tidal tails is most prominent in those ULIGs that have double nuclei, suggesting that the star formation rate in the tails peaks prior to the actual coalescence of the galaxy nuclei and diminishes quickly thereafter. Similar to results at other wavelengths, the observed star formation at U' can account for only a small fraction of the known bolometric luminosity of the ULIGs. Azimuthally averaged radial light profiles at U' are characterized by a Sersic law with index n = 2, which is intermediate between an exponential disk and an r-1/4 law and closely resembles the latter at large radii. The implications of this near-ultraviolet imaging for optical/near-infrared observations of high-redshift counterparts of ULIGs are discussed.

An Ultraviolet and Near‐Infrared View of NGC 4214: A Starbursting Core Embedded in a Low Surface Brightness Disk

During the Astro-2 Spacelab mission in 1995 March, the Ultraviolet Imaging Telescope (UIT) obtained far-UV (λ = 1500 A) imagery of the nearby Sm/Im galaxy NGC 4214. The UIT images have a spatial resolution of ~3'' and a limiting surface brightness, μ1500 > 25 mag arcsec-2, permitting detailed investigation of the intensity and spatial distribution of the young, high-mass stellar component. These data provide the first far-UV imagery covering the full spatial extent of NGC 4214. Comparison with a corresponding I-band image reveals the presence of a starbursting core embedded in an extensive low surface brightness disk. In the far-UV (FUV), NGC 4214 is resolved into several components: a luminous, central knot; an inner region (r 2.5 kpc) with ~15 resolved sources embedded in bright, diffuse emission; and a population of fainter knots extending to the edge of the optically defined disk (r ≈ 5 kpc). The FUV light, which traces recent massive star formation, is observed to be more centrally concentrated than the I-band light, which traces the global stellar population. The FUV radial light profile is remarkably well represented by an R1/4 law, providing evidence that the centrally concentrated massive star formation in NGC 4214 is the result of an interaction, possibly a tidal encounter, with a dwarf companion(s). The brightest FUV source produces ~8% of the global FUV luminosity. This unresolved source, corresponding to the Wolf-Rayet knot described by Sargent & Filippenko, is located at the center of the FUV light distribution, giving NGC 4214 an active galactic nucleus-like morphology. Another strong source is present in the I band, located 19'' west, 10'' north of the central starburst knot, with no FUV counterpart. The I-band source may be the previously unrecognized nucleus of NGC 4214 or an evolved star cluster with an age greater than ~200 Myr. The global star formation rate derived from the total FUV flux is consistent with rates derived using data at other wavelengths and lends support to the scenario of roughly constant star formation during the last few hundred million years at a level significantly enhanced relative to the lifetime averaged star formation rate. The hybrid disk/starburst-irregular morphology evident in NGC 4214 emphasizes the danger of classifying galaxies based on their high surface brightness components at any particular wavelength.

Multi‐colour surface photometry of a sample of HI‐detected late type galaxies

AbstractWe perform BV RI surface photometry of 27 late type spiral and dwarf galaxies. All but two galaxies are selected from the HI‐survey of Schneider et al. (1990). We derive integral photometric parameters and the radial light and colour profiles and compare them to those of several LSB and bright field galaxy samples. Our new data confirm the earlier suggestions that the ‘ Schneider's sample’ consists of two different types of galaxies, with probably different star formation histories. First, the nearby (v0 ⩽ 1600 km s‐ 1) galaxies are mostly true dwarfs with the mean absolute magnitude of MB = ‐ 14.9±1.5 and with disk scale lengthes smaller than 1 kpc. These dwarfs are reasonably blue with median B – V = 0.49 and contain a large amount of neutral gas. Second, the distant (v0 ⩾ 4500 km s‐ 1) galaxies are late type LSB galaxies with typical face‐on disk central surface brightnesses of about 23.3 B‐ mag arcsec‐ 2 and ‘ normal’ disk scale lengthes of 3.6±1.5 kpc. Observed LSB galaxies are significantly redder, with median B – V ⋍ 0.72, than are the typical field LSB galaxies. The observed LSB galaxies are rich in HI but the current star formation activity is probably low.

Structure of the globular clusters in the Fornax dwarf elliptical galaxy

view Abstract Citations (17) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structure of The Globular Cluster in The Fornax Dwarf Elliptical Galaxy Rodgers, A. W. ; Roberts, W. H. Abstract We have measured the radial light profiles of the five brighter clusters in the Fornax dwarf elliptical galaxy. We find that the clusters fall into two structural groups. Hodge clusters Nos. 1 and 2 have similar core radii which are twice the core radii of clusters Nos. 3, 4, and 5. Clusters Nos. 1 and 2 appear to fit truncated King models. Clusters Nos. 3, 4, and 5 do not fit the King models but show an extended halo structure with no evidence of tidal truncation. We conjecture that clusters Nos. 1 and 2 have interacted dynamically with each other while the other clusters have had no such interaction over their lifetime. Publication: The Astronomical Journal Pub Date: May 1994 DOI: 10.1086/116982 Bibcode: 1994AJ....107.1737R Keywords: Astronomical Photometry; Dwarf Galaxies; Elliptical Galaxies; Galactic Structure; Globular Clusters; Radial Distribution; Stellar Luminosity; Charge Coupled Devices; Data Reduction; Optical Filters; Telescopes; Astronomy; GALAXIES: PECULIAR; GLOBULAR CLUSTERS: GENERAL; GALAXIES: INDIVIDUAL: FORNAX full text sources ADS | data products SIMBAD (6) NED (6)