- 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.
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Search Results
- 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.
2614. 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/52
- Title:
- NGFS. III. Dwarf galaxies in outer regions
- Short Name:
- J/ApJ/859/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 271 previously undetected dwarf galaxies in the outer Fornax cluster regions at radii r_vir_/4<r<r_vir_/2 using data from the Next Generation Fornax Survey (NGFS) with deep coadded u', g', and i' images obtained with Blanco/DECam at Cerro Tololo Interamerican Observatory. From the 271 dwarf candidates, we find 39 to be nucleated. Together with our previous study of the central Fornax region, the new dwarfs detected with NGFS data number 392, of which 56 are nucleated. The total Fornax dwarf galaxy population from NGFS and other catalogs rises, therefore, to a total of 643 with 181 being nucleated, yielding an overall nucleation fraction of 28%. The absolute i'-band magnitudes for the outer NGFS dwarfs are in the range -18.80<=M_i'_<=-8.78 with effective radii r_eff,i'_=0.18-2.22kpc and an average Sersic index <n>_i'_=0.81. Nonnucleated dwarfs are found to be fainter and smaller by {Delta}<M_i'_>=2.25mag and {Delta}<r_eff,i'_>=0.4kpc than the nucleated dwarfs. We demonstrate a significant clustering of dwarf galaxies on scales <~100kpc, and projected surface number density profile estimates, {Sigma}_N_(r), show a concentration of dwarfs in the Fornax core region within r<~350kpc. {Sigma}_N_(r) has a flat distribution up to ~350kpc, beyond which it declines for the nonnucleated dwarfs. The nucleated dwarfs have a steeper {Sigma}N(r) distribution, are more concentrated toward NGC 1399, and are decreasing rapidly outwards. This is the first time the transition from cluster to field environment has been established for the very faint dwarf galaxy population with robust sample statistics.
2618. NG5907 images
- ID:
- ivo://CDS.VizieR/J/A+A/632/L13
- Title:
- NG5907 images
- Short Name:
- J/A+A/632/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar streams are regarded as crucial objects to test galaxy formation models, with their morphology tracing the underlying potentials and their occurrence tracking the assembly history of the galaxies. The existence of one of the most iconic stellar streams, the double loop around NGC5907, has recently been questioned by new observations with the Dragonfly telescope. This new work only finds parts of the stream, even though they reach a 1 sigma surface brightness limit of 30.3 mag per sq. arcsec in the g-band. Using 7.2 hours of Luminance L-band imaging with the Milankovic 1.4 meter telescope, we have re-observed the putative double loop part to confirm or reject this assessment. We do not find signs of the double loop, but see only a single, knee-shaped stellar stream. Comparing our to the data by the Dragonfly team, we find the same features. Our observations reach a 1 sigma surface brightness limit of 29.7 mag per sq. arcsec in the g-band. These findings emphasize the need for independent confirmation of detections of very low-surface brightness features.
- ID:
- ivo://CDS.VizieR/J/ApJ/802/30
- Title:
- NGVS VI. Ultra-compact dwarfs in M87
- Short Name:
- J/ApJ/802/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of ultra-compact dwarfs (UCDs; r_h_>~10pc) --objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies-- has been hotly debated in the 15yrs since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme star clusters, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs and 911 GCs associated with the central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M_*_>~2x10^6^M_{sun}_ and 92% are as blue as the classic blue GCs, nearly triple the confirmed sample of Virgo UCDs, providing by far the best opportunity for studying global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of blue GCs in the inner ~70kpc and as steep as that of red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than GCs, and blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have an orbital anisotropy profile that is tangentially biased at radii <~40kpc and radially biased farther out, whereas blue GCs become more tangentially biased at larger radii beyond ~40kpc; (4) GCs with M_*_>~2x10^6^M_{sun}_ have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially biased orbital structure of UCDs at large radii is in general agreement with the "tidally threshed dwarf galaxy" scenario.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/18
- Title:
- NGVS. XXIII. Nuclear star clusters
- Short Name:
- J/ApJ/878/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using deep, high-resolution optical imaging from the Next Generation Virgo Cluster Survey, we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 10^5^<~M*/M_{sun}_<~10^12^. The nucleation fraction reaches a peak value f_n_~90% for M*~10^9^M_{sun}_ galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as M*~5x10^5^M_{sun}_. Comparison with literature data for nearby groups and clusters shows that at the low-mass end nucleation is more frequent in denser environments. The NSC mass function peaks at M_NSC_~7x10^5^M_{sun}_, a factor 3-4 times larger than the turnover mass for globular clusters (GCs). We find a nonlinear relation between the stellar masses of NSCs and those of their host galaxies, with a mean nucleus-to-galaxy mass ratio that drops to M_NSC_/M*~3.6x10^-3^ for M*~5x10^9^M_{sun}_ galaxies. Nuclei in both more and less massive galaxies are much more prominent: M_NSC_{propto}M_*_^0.46^ at the low-mass end, where nuclei are nearly 50% as massive as their hosts. We measure an intrinsic scatter in NSC masses at a fixed galaxy stellar mass of 0.4dex, which we interpret as evidence that the process of NSC growth is significantly stochastic. At low galaxy masses we find a close connection between NSCs and GC systems, including very similar occupation distributions and comparable total masses. We discuss these results in the context of current dissipative and dissipationless models of NSC formation.
