- ID:
- ivo://CDS.VizieR/J/A+A/515/A55
- Title:
- NGC 6334-NGC 6357 complex
- Short Name:
- J/A+A/515/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our knowledge of high-mass star formation has been mainly based on follow-up studies of bright sources found by IRAS, and has thus been incomplete for its earliest phases, which are inconspicuous at infrared wavelengths. With a new generation of powerful bolometer arrays, unbiased large-scale surveys of nearby high-mass star-forming complexes now search for the high-mass analog of low-mass cores and class 0 protostars. Following the pioneering study of Cygnus X, we investigate the star-forming region NGC 6334-NGC 6357 (~1.7kpc)
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/516/A4
- Title:
- NGC1600, NGC4125, NGC7619 extended spectroscopy
- Short Name:
- J/A+A/516/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high quality long slit spectra along the major and minor axes out to 1.5-2R_e_ (14-22kpc) of three bright elliptical galaxies (NGC1600, NGC4125, NGC7619) obtained at the Hobby-Eberly Telescope (HET). We derive stellar kinematic profiles and Lick/IDS indices (H{beta}, Mgb, Fe_{5015}, Fe_{5270}, Fe_{5335}, Fe_{5406}). Moreover, for NGC4125 we derive gas kinematics and emission line strengths. We model the absorption line strengths using Simple Stellar Populations models that take into account the variation of {alpha}/Fe and derive ages, total metallicity and element abundances. Overall, we find that the three galaxies have old and {alpha}/Fe overabundant stellar populations with no significant gradients. The metallicity is supersolar at the center with a strong negative radial gradient. For NGC4125, several pieces of evidence point to a recent dissipational merger event. We calculate the broad band color profiles with the help of SSP models. All of the colors show sharp peaks at the center of the galaxies, mainly caused by the metallicity gradients, and agree well with the measured colors. Using the Schwarzschild's axisymmetric orbit superposition technique, we model the stellar kinematics to constrain the dark halos of the galaxies. We use the tight correlation between the Mgb strength and local escape velocity to set limits on their extent by testing different halo sizes. Logarithmic halos cut at 60kpc minimize the overall scatter of the Mgb-V_esc_ relation. Larger cutoff radii are found if the dark matter density profile is decreasing more steeply at large radii.
- ID:
- ivo://CDS.VizieR/J/A+A/314/43
- Title:
- NGC 5548 Profile variability
- Short Name:
- J/A+A/314/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical emission line intensities of the variable Seyfert 1 galaxy NGC 5548 are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A101
- Title:
- NGC6656 spectroscopy of 71 blue HB stars
- Short Name:
- J/A+A/559/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent investigations revealed very peculiar properties of blue horizontal branch (HB) stars in {omega} Centauri, which show anomalously low surface gravity and mass compared to other clusters and to theoretical models. {omega} Centauri, however, is a very unusual object, hosting a complex mix of multiple stellar populations with different metallicity and chemical abundances. We measured the fundamental parameters (temperature, gravity, and surface helium abundance) of a sample of 71 blue HB stars in M 22, with the aim of clarifying if the peculiar results found in {omega} Cen are unique to this cluster. M 22 also hosts multiple sub-populations of stars with a spread in metallicity, analogous to {omega} Cen.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A103
- Title:
- NGC 3532 stars cChromospheric activity
- Short Name:
- J/A+A/656/A103
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The coeval stars of young open clusters provide insights into the formation of the rotation-activity relationship that elude studies of multi-age field populations. We measure the chromospheric activity of cool stars in the 300 Myr old open cluster NGC 3532 in concert with their rotation periods to study the mass-dependent morphology of activity for this transitional coeval population. Using multi-object spectra of the Ca II infrared triplet region obtained with the AAOmega spectrograph at the 4m Anglo- Australian Telescope, we measure the chromospheric emission ratios R'_IRT_ for 454 FGKM cluster members of NGC3532. The morphology of activity against colour appears to be a near-mirror image of the cluster's rotational behaviour. In particular, we identify a group of 'desaturated transitional rotators' that branches off from the main group of unsaturated FGK slow rotators, and from which it is separated by an 'activity gap'. The few desaturated gap stars are identical to the ones in the rotational gap. Nevertheless, the rotation-activity diagram is completely normal. In fact, the relationship is so tight that it allows us to predict rotation periods for many additional stars. We then precisely determine these periods from our photometric light curves, allowing us to construct an enhanced colour-period diagram that represents 66% of the members in our sample. Our activity measurements show that all fast rotators of near-solar mass (F-G type) have evolved to become slow rotators, demonstrating that the absence of fast rotators in a colour-period diagram is not a detection issue but an astrophysical fact. We also identify a new population of low-activity stars among the early Mdwarfs, enabling us to populate the extended slow rotator sequence in the colour-period diagram. The joint analysis of chromospheric activity and photometric time series data thus enables comprehensive insights into the evolution of the rotation and activity of stars during the transitional phase between the Pleiades and Hyades ages.
- 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.
- 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.
- 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.
- 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.
- 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_.
