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2551. NGC 5427 WiFeS data cubes
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.
2552. 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.
2553. NGC 5548 43 year-long monitoring in H{beta}
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 This includes 12 years of new unpublished observations (2003 to 2015).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.
2554. NGC 247 young stellar population
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.
2555. NGFS. III. Dwarf galaxies in outer regions
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.
2556. 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.
2557. NGVS VI. Ultra-compact dwarfs in M87
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.
2558. NGVS. XXIII. Nuclear star clusters
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.
2559. NIBLES bivariate luminosity function
ID:
ivo://CDS.VizieR/J/A+A/642/A175
Title:
NIBLES bivariate luminosity function
Short Name:
J/A+A/642/A175
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a modified optical luminosity-HI mass bivariate luminosity function (BLF) based on HI line observations from the Nancay Interstellar Baryons Legacy Extragalactic Survey (NIBLES), including data from our new, four times more sensitive follow-up HI line observations obtained with the Arecibo radio telescope. The follow-up observations were designed to probe the underlying HI mass distribution of the NIBLES galaxies that were undetected or marginally detected in HI at the Radio Telescope. Our total follow-up sample consists of 234 galaxies, and it spans the entire luminosity and color range of the parent NIBLES sample of 2600 nearby (900<cz<12000km/s) SDSS galaxies. We incorporated the follow-up data into the bivariate analysis by scaling the NIBLES undetected fraction by an Arecibo-only distribution. We find the resulting increase in low HI mass-to-light ratio densities to be about 10% for the bins -1.0<=log(M/L)<=-0.5, which produces an increased HI mass function (HIMF) low mass slope of {alpha}=-1.14+/-0.07, being slightly shallower than the values of -1.35+/-0.05 obtained by recent blind HI surveys. Applying the same correction to the optically corrected bivariate luminosity function from our previous paper produces a larger density increase of about 0.5 to 1dex in the lowest HI mass-to-light ratio bins for a given luminosity while having a minimal effect on the resulting HIMF low mass slope, which still agrees with blind survey HIMFs. This indicates that while low HI-mass-to-light ratio galaxies do not contribute much to the one-dimensional HIMF, their inclusion has a significant impact on the densities in the two-dimensional distribution.
2560. NIBLES II. Arecibo follow-up observations
ID:
ivo://CDS.VizieR/J/A+A/596/A60
Title:
NIBLES II. Arecibo follow-up observations
Short Name:
J/A+A/596/A60
Date:
21 Oct 2021
Publisher:
CDS
Description:
We obtained Arecibo HI line follow-up observations of 154 of the 2600 galaxies in the Nancay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) sample. These observations are on average four times more sensitive than the original observations at the Nancay Radio Telescope. The main goal of this survey is to characterize the underlying HI properties of the NIBLES galaxies which were undetected or marginally detected at Nancay. Of the Nancay non-detections, 85% were either clearly or marginally detected at Arecibo, while 89% of the Nancay marginal detections were clearly detected. Based on the statistics of the detections relative to g-i color and r-band luminosity (Lr) distribution among our Arecibo observations, we anticipate ~60% of our 867 Nancay non-detections and marginal detections could be detected at the sensitivity of our Arecibo observations. Follow-up observations of our low luminosity (Lr<10^8.5^L_{sun}_) blue sources indicate that they have, on average, more concentrated stellar mass distributions than the Nancay detections in the same luminosity range, suggesting we may be probing galaxies with intrinsically different properties. These follow-up observations enable us to probe HI mass fractions, log(MHI/M*) 0.5dex and 1dex lower, on average, than the NIBLES and ALFALFA surveys respectively.