- ID:
- ivo://CDS.VizieR/J/MNRAS/487/3776
- Title:
- NGC 3115 Stellar Populations and Kinematics
- Short Name:
- J/MNRAS/487/3776
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a combination of the Schwarzschild orbit-superposition dynamical modelling technique with the spatially-resolved mean stellar age and metallicity maps to uncover the formation history of galaxies. We apply this new approach to a remarkable 5-pointing mosaic of VLT/MUSE observations obtained by Guerou et al. (2016A&A...591A.143G, Cat. J/A+A/591/A143) extending to a maximum galactocentric distance of ~120'' (5.6kpc) along the major axis, corresponding to ~2.5R_e. Our method first identifies 'families' of orbits from the dynamical model that represent dynamically distinct structures of the galaxy. Individual ages and metallicities of these components are then fit for using the stellar-population information. Our results highlight components of the galaxy that are distinct in the combined stellar dynamics/populations space, which implies distinct formation paths. We find evidence for a dynamically-cold, metal-rich disk, consistent with a gradual in-situ formation. This disk is embedded in a generally-old population of stars, with kinematics ranging from dispersion-dominated in the centre to an old, diffuse, metal-poor stellar halo at the extremities. We find also a direct correlation between the dominant dynamical support of these components, and their associated age, akin to the relation observed in the Milky Way. This approach not only provides a powerful model for inferring the formation history of external galaxies, but also paves the way to a complete population-dynamical model.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/632/A10
- Title:
- NGC 4631 total intensity images
- Short Name:
- J/A+A/632/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 4631 is an interacting galaxy that exhibits one of the largest, gaseous halos observed among edge-on galaxies. We aim to examine the synchrotron and cosmic-ray propagation properties of its disk and halo emission with new radio continuum data. Radio continuum observations of NGC 4631 were performed with the Karl G. Jansky Very Large Array at C-band (5.99GHz) in the C and D array configurations, and at L-band (1.57GHz) in the B, C, and D array configurations. Complementary observations of NGC 4631 with the Effelsberg telescope were performed at 1.42 and 4.85 GHz. The interferometric total intensity data were combined with the single-dish Effelsberg data in order to recover the missing large-scale total power emission. The thermal and nonthermal components of the total radio emission were separated by estimating the thermal contribution through the extinction-corrected H{alpha} emission. The H{alpha} radiation was corrected for extinction using a linear combination of the observed H{alpha} and 24{mu}m data. NGC 4631 has a global thermal fraction at 5.99(1.57)GHz of 14+/-3% (5.4+/-1.1%). The mean scale heights of the total emission in the radio halo (thick disk) at 5.99(1.57)GHz are 1.79+/-0.54kpc (1.75+/-0.27kpc) and have about the same values for the synchrotron emission. The total magnetic field of NGC 4631 has a mean strength of <Beq>~=9{mu}G in the disk, and a mean strength of <Beq>~=7{mu}G in the halo. We also studied a double-lobed background radio galaxy southwest of NGC 4631, which is an FR II radio galaxy according to the distribution of spectral index across the lobes. From the halo scale heights we estimated that the radio halo is escape-dominated with convective cosmic ray propagation, and conclude that there is a galactic wind in the halo of NGC 4631.
- ID:
- ivo://CDS.VizieR/J/A+A/371/79
- Title:
- NGC 5548 UBVRI phot. and Halpha, Hbeta fluxes
- Short Name:
- J/A+A/371/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a ground-based optical monitoring campaign on NGC 5548 in June 1998 are presented. The broad-band fluxes (U, B, V), and the spectrophotometric optical continuum flux F_{lambda}_ (5100{AA}) monotonically decreased in flux while the broad-band R and I fluxes and the integrated emission-line fluxes of H{alpha} and H{beta} remained constant to within 5%. On June 22, a short continuum flare was detected in the broad band fluxes. It had an amplitude of about ~18% and it lasted only =~90 min. The broad band fluxes and the optical continuum F_{lambda}_ (5100{AA}) appear to vary simultaneously with the EUV variations. No reliable delay was detected for the broad optical emission lines in response to the EUVE variations. Narrow H{beta} emission features predicted as a signature of an accretion disk were not detected during this campaign. However, there is marginal evidence for a faint feature at {lambda}=~4962{AA} with FWHM=~6{AA} redshifted by {Delta}v=~1100km/s with respect to H{beta}_narrow_.
2544. NGC 891 70-500um images
- ID:
- ivo://CDS.VizieR/J/A+A/565/A4
- Title:
- NGC 891 70-500um images
- Short Name:
- J/A+A/565/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the connection between dust and gas in the nearby edge-on spiral galaxy NGC 891, a target of the Very Nearby Galaxies Survey. High resolution Herschel Space Observatory PACS and SPIRE 70, 100, 160, 250, 350, and 500 micron images are combined with JCMT SCUBA 850 micron observations to trace the far-infrared/submillimetre spectral energy distribution (SED). Maps of the HI 21cm line and CO(J=3-2) emission trace the atomic and molecular hydrogen gas, respectively. We fit one-component modified blackbody models to the integrated SED, finding a global dust mass of (8.5+/-2.0)x10^7^M_{sun}_ and an average temperature of 23+/-2K, consistent with results from previous far-infrared experiments. We also fit one-component modified blackbody models to pixel-by-pixel SEDs to produce maps of the dust mass and temperature. A comparison of the dust properties with the gaseous components of the ISM reveals strong spatial correlations between the surface mass densities of dust and the molecular hydrogen and total gas surface densities.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A98
- Title:
- NGC 2683 VLA C and D datacubes
- Short Name:
- J/A+A/586/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80{deg}; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination between 10kpc<=R<=20kpc (decreasing by 10{deg}); (iv) an exponential flare that rises from 0.5kpc at R=9kpc to 4kpc at R=15kpc, stays constant until R=22kpc, and decreases its height for R>22kpc; and (v) a low surface-density gas ring with a vertical offset of 1.3kpc. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the optical and thin gas disk. Under the assumption of vertical hydrostatic equilibrium we derive the vertical velocity dispersion of the gas. The high turbulent velocity dispersion in the flare can be explained by energy injection by (i) supernovae; (ii) magneto-rotational instabilities; (iii) interstellar medium stirring by dark matter substructure; or (iv) external gas accretion. The existence of the complex large-scale warping and asymmetries favors external gas accretion as one of the major energy sources that drives turbulence in the outer gas disk. We propose a scenario where this external accretion leads to turbulent adiabatic compression that enhances the turbulent velocity dispersion and might quench star formation in the outer gas disk of NGC 2683.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A43
- Title:
- NGC 4418/VV 655 HI images
- Short Name:
- J/A+A/607/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The galaxy NGC4418 harbours a compact (<20pc) core with a very high bolometric luminosity (~10^11^L_{sun}_). As most of the galaxy's energy output comes from this small region, it is of interest to determine what fuels this intense activity. An interaction with the nearby blue irregular galaxy VV655 has been proposed, where gas aquired by NGC4418 could trigger intense star formation and/or black hole accretion in the centre. We aim to constrain the interaction hypothesis by studying neutral hydrogen structures which could reveal tails and debris connecting NGC4418 to the nearby galaxy VV655. We present observations at 1.4GHz with the Very Large Array (VLA) of radio continuum as well as emission and absorption from atomic hydrogen. Gaussian distributions are fitted to observed HI emission and absorption spectra.We estimate the star formation rate (SFR) of NGC4418 and VV655 from the 1.4GHz radio emission and compare with estimates from archival 70um Herschel observations.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A41
- Title:
- NGC 5427 WiFeS data cubes
- Short Name:
- J/A+A/566/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the nearby, nearly face-on, Seyfert 2 galaxy, NGC 5427, using optical integral field spectroscopy of both the nuclear regions and the HII regions in the spiral arms. The observed spectra have been modelled using the MAPPINGS IV photoionisation code, both to derive the chemical abundances in the HII regions and the Seyfert nucleus, and to constrain the EUV spectral energy distribution of the AGN illuminating the extended narrow-line region.
2548. NGC253 XMM observations
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/849
- Title:
- NGC253 XMM observations
- Short Name:
- J/MNRAS/388/849
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 253 is a local, starbursting spiral galaxy with strong X-ray emission from hot gas, as well as many point sources. We have conducted a spectral survey of the X-ray population of NGC 253 using a deep XMM-Newton observation. NGC 253 only accounts for ~20 per cent of the XMM-Newton EPIC field of view, allowing us to identify ~100 X-ray sources that are unlikely to be associated with NGC 253. Hence, we were able to make a direct estimate of contamination from, for example, foreground stars and background galaxies. X-ray luminosity functions (XLFs) of galaxy populations are often used to characterize their properties. There are several methods for estimating the luminosities of X-ray sources with few photons. We have obtained spectral fits for the brightest 140 sources in the 2003 XMM-Newton observation of NGC 253, and compare the best-fitting luminosities of those 69 non-nuclear sources associated with NGC 253 with luminosities derived using other methods. We find the luminosities obtained from these various methods to vary systematically by a factor of up to 3 for the same data; this is largely due to differences in absorption. We therefore conclude that assuming Galactic absorption is probably unwise; rather, one should measure the absorption for the population.
- ID:
- ivo://CDS.VizieR/J/ApJS/225/29
- Title:
- NGC 5548 43 year-long monitoring in H{beta}
- Short Name:
- J/ApJS/225/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 H{beta} spectra and analyzed the long-term spectral variations of the 5100 A continuum and the H{beta} line. Our analysis is based on standard procedures, including the Lomb-Scargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a ~5700 day periodicity in the continuum light curve, the H{beta} light curve, and the radial velocity curve of the red wing of the H{beta} line. The data are consistent with orbital motion inside the broad emission line region of the source. We discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A35
- Title:
- NGC 247 young stellar population
- Short Name:
- J/A+A/626/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to investigate the characteristics of the young stellar population in the spiral galaxy NGC 247. In particular, we focused our attention in its hierarchical clustering distributions and the properties of the smallest groups. We used multiband Hubble Space Telescope (HST) data from three fields covering more than half of NGC 247 to select the young population. Then, through the path linkage criterion (PLC), we found compact young star groups and estimated their fundamental parameters, such as their stellar densities, sizes, number of members, and luminosity function (LF) slopes. We also performed a fractal analysis to determinate the clustering properties of this population. We built a stellar density map and dendrograms corresponding to the galactic young population to detect large structures and depict their main characteristics. We detect 339 young star groups, for which we compute a mean radius of ~60pc and a maximum size distribution between 30 and 70pc. We also obtain LF slopes with a bimodal distribution showing peaks at ~0.1 and ~0.2. We identify several candidates for HII regions that follow an excellent spatial correlation with the young groups found by the PLC. We observe that the young populations are hierarchically organized, wherein the smaller and denser structures are within larger and less dense structures. We notice that all these groups present a fractal subclustering, following the hierarchical distribution observed in the corresponding stellar density map. For the large young structures observed in this map, we obtain a fractal dimension of ~1.6-1.8 using the perimeter-area relation and cumulative size distribution. These values are consistent with a scenario of hierarchical star formation.