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1801. NGC 6397 stars MUSE spectra
ID:
ivo://CDS.VizieR/J/A+A/588/A148
Title:
NGC 6397 stars MUSE spectra
Short Name:
J/A+A/588/A148
Date:
23 Mar 2022 16:26:54
Publisher:
CDS
Description:
We demonstrate the high multiplex advantage of crowded field 3D spectroscopy with the new integral field spectrograph MUSE by means of a spectroscopic analysis of more than 12000 individual stars in the globular cluster NGC 6397. The stars are deblended with a point spread function fitting technique, using a photometric reference catalogue from HST as prior, including relative positions and brightnesses. This catalogue is also used for a first analysis of the extracted spectra, followed by an automatic in-depth analysis via a full-spectrum fitting method based on a large grid of PHOENIX spectra. We analysed the largest sample so far available for a single globular cluster of 18 932 spectra from 12 307 stars in NGC 6397. We derived a mean radial velocity of v_rad_=17.84+/-0.07km/s and a mean metallicity of [Fe/H]=-2.120+/-0.002, with the latter seemingly varying with temperature for stars on the red giant branch (RGB). We determine Teff and [Fe/H] from the spectra, and log g from HST photometry. This is the first very comprehensive Hertzsprung-Russell diagram (HRD) for a globular cluster based on the analysis of several thousands of stellar spectra, ranging from the main sequence to the tip of the RGB. Furthermore, two interesting objects were identified; one is a post-AGB star and the other is a possible millisecond-pulsar companion.
1802. NGC1271 stellar kinematics
ID:
ivo://CDS.VizieR/J/ApJ/808/183
Title:
NGC1271 stellar kinematics
Short Name:
J/ApJ/808/183
Date:
21 Oct 2021
Publisher:
CDS
Description:
Located in the Perseus cluster, NGC 1271 is an early-type galaxy with a small effective radius of 2.2kpc and a large bulge stellar velocity dispersion of 276km/s for its K-band luminosity of 8.9x10^10^L_{sun}_. We present a mass measurement for the black hole in this compact, high-dispersion galaxy using observations from the Near-infrared Integral Field Spectrometer on the Gemini North telescope assisted by laser guide star adaptive optics, large-scale integral field unit observations with PPAK at the Calar Alto Observatory, and Hubble Space Telescope WFC3 imaging observations. We are able to map out the stellar kinematics both on small spatial scales, within the black hole sphere of influence, and on large scales that extend out to four times the galaxy's effective radius. We find that the galaxy is rapidly rotating and exhibits a sharp rise in the velocity dispersion. Through the use of orbit-based stellar dynamical models, we determine that the black hole has a mass of (3.0^+1.0^_-1.1_)x10^9^M_{sun}_ and the H-band stellar mass-to-light ratio is 1.40^+0.13^_-0.11_{gamma}_{sun}_ ({sigma} uncertainties). NGC 1271 occupies the sparsely populated upper end of the black hole mass distribution but is very different from the brightest cluster galaxies (BCGs) and giant elliptical galaxies that are expected to host the most massive black holes. Interestingly, the black hole mass is an order of magnitude larger than expectations based on the galaxy's bulge luminosity but is consistent with the mass predicted using the galaxy's bulge stellar velocity dispersion. More compact, high-dispersion galaxies need to be studied using high spatial resolution observations to securely determine black hole masses, as there could be systematic differences in the black hole scaling relations between these types of galaxies and the BCGs/giant ellipticals, thereby implying different pathways for black hole and galaxy growth.
1803. NGC 2808 stellar population spectra
ID:
ivo://CDS.VizieR/J/A+A/631/A14
Title:
NGC 2808 stellar population spectra
Short Name:
J/A+A/631/A14
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galactic globular clusters (GCs) are now known to host multiple populations displaying particular abundance variations. The different populations within a GC can be well distinguished following their position in the pseudo two-colors diagrams, also referred to as "chromosome maps". These maps are constructed using optical and near-UV photometry available from the Hubble Space Telescope (HST) UV survey of GCs. However, the chemical tagging of the various populations in the chromosome maps is hampered by the fact that HST photometry and elemental abundances are both available only for a limited number of stars. The spectra collected as part of the MUSE survey of globular clusters provide a spectroscopic counterpart to the HST photometric catalogs covering the central regions of GCs. In this paper, we use the MUSE spectra of 1155 red giant branch (RGB) stars in NGC 2808 to characterize the abundance variations seen in the multiple populations of this cluster. We use the chromosome map of NGC 2808 to divide the RGB stars into their respective populations. We then combine the spectra of all stars belonging to a given population, resulting in one high signal-to-noise ratio spectrum representative of each population. Variations in the spectral lines of O, Na, Mg, and Al are clearly detected among four of the populations. In order to quantify these variations, we measured equivalent width differences and created synthetic populations spectra that were used to determine abundance variations with respect to the primordial population of the cluster. Our results are in good agreement with the values expected from previous studies based on high-resolution spectroscopy. We do not see any significant variations in the spectral lines of Ca, K, and Ba. We also do not detect abundance variations among the stars belonging to the primordial population of NGC 2808.
1804. NGC2264 structure and star formation history
ID:
ivo://CDS.VizieR/J/A+A/609/A10
Title:
NGC2264 structure and star formation history
Short Name:
J/A+A/609/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. We aim to explore the structure of the open cluster and star-forming region NGC 2264 (~3Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8M_{sun}_ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters.
1805. NGC 5548 UBVRI phot. and Halpha, Hbeta fluxes
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_.
1806. NGC6791 V604 Lyr disentangled component spectra
ID:
ivo://CDS.VizieR/J/A+A/649/A178
Title:
NGC6791 V604 Lyr disentangled component spectra
Short Name:
J/A+A/649/A178
Date:
22 Feb 2022
Publisher:
CDS
Description:
Models of stellar structure and evolution can be constrained using accurate measurements of the parameters of eclipsing binary members of open clusters. Multiple binary stars provide the means to tighten the constraints, and in turn, to improve the precision and accuracy of the age estimate of the host cluster. In the previous two papers of this series, we demonstrated the use of measurements of multiple eclipsing binaries in the old open cluster NGC6791 to set tighter constraints on the properties of stellar models than was previously possible, thereby improving both the accuracy and precision of the cluster age. We identify and measure the properties of a non-eclipsing cluster member, V56 (Cl* NGC 6791 KR V56), in NGC 6791 and demonstrate how this provides additional model constraints that support and strengthen our previous findings. We analyse multi-epoch spectra of V56 from FLAMES in conjunction with the existing photometry and measurements of eclipsing binaries in NGC6971. The parameters of the V56 components are found to be Mp=1.103+/-0.008M_{sun}_ and Ms=0.974+/-0.007M_{sun}_, Rp=1.764+/-0.099R_{sun}_ and Rs=1.045+/-0.057R_{sun}_, Teff,p=5447+/-125K and Teff,s=5552+/-125K, and surface [Fe/H]=+0.29+/-0.06 assuming that they have the same abundance. The derived properties strengthen our previous best estimate of the cluster age of 8.3+/-0.3Gyr and the mass of stars on the lower RGB, M_RGB_=1.15+/-0.02M_{sun}_ for NGC 6791. These numbers therefore continue to serve as verification points for other methods of age and mass measures, such as asteroseismology.
1807. 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.
1808. NGC 7469 X-ray spectra
ID:
ivo://CDS.VizieR/J/A+A/615/A72
Title:
NGC 7469 X-ray spectra
Short Name:
J/A+A/615/A72
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the physical structure of the active galactic nucleus (AGN) wind in the Seyfert-1 galaxy NGC 7469 through high-resolution X-ray spectroscopy with Chandra HETGS and photoionisation modelling. Contemporaneous data from Chandra, HST, and Swift are used to model the optical-UV-X-ray continuum and determine the spectral energy distribution (SED) at two epochs, 13yr apart. For our investigation we use new observations taken in December 2015-January 2016, and historical ones taken in December 2002. We study the impact of a change in the SED shape, seen between the two epochs, on the photoionisation of the wind. The HETGS spectroscopy shows that the AGN wind in NGC 7469 consists of four ionisation components, with their outflow velocities ranging from -400 to -1800km/s. From our modelling we find that the change in the ionising continuum shape between the two epochs results in some variation in the ionisation state of the wind components. However, for the main ions detected in X-rays, the sum of their column densities over all components remains in practice unchanged. For two of the four components, which are found to be thermally unstable in both epochs, we obtain 2<r<31pc and 12<r<29pc using the cooling and recombination timescales. For the other two thermally stable components, we obtain r<31pc and r<80pc from the recombination timescale. The results of our photoionisation modelling and thermal stability analysis suggest that the absorber components in NGC 7469 are consistent with being a thermally driven wind from the AGN torus. Finally, from analysis of the zeroth-order ACIS/HETG data, we discover that the X-ray emission in the range 0.2-1keV is spatially extended over 1.5-12". This diffuse soft X-ray emission is explained by coronal emission from the nuclear starburst ring in NGC 7469. The star formation rate inferred from this diffuse soft X-ray emission is consistent with those found by far-infrared studies of NGC 7469.
1809. 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.
1810. 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.

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