- ID:
- ivo://CDS.VizieR/J/A+A/579/A4
- Title:
- MCS J1206.2-0847 galaxies spectral classification
- Short Name:
- J/A+A/579/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the effort to understand the link between the structure of galaxy clusters and their galaxy populations, we focus on MACS J1206.2-0847 at z~0.44 and probe its substructure in the projected phase space through the spectrophotometric properties of a large number of galaxies from the CLASH-VLT survey. Our analysis is mainly based on an extensive spectroscopic dataset of 445 member galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme, sampling the cluster out to a radius ~2R200 (4Mpc). We classify 412 galaxies as passive, with strong Hdelta absorption (red and blue galaxies), and with emission lines from weak to very strong. A number of tests for substructure detection are applied to analyze the galaxy distribution in the velocity space, in 2D space, and in 3D projected phase-space. The observational scenario agrees with MACS J1206.2-0847 having WNW-ESE as the direction of the main cluster accretion, traced by passive galaxies and red strong H{delta} galaxies. The red strong H{delta} galaxies, interpreted as poststarburst galaxies, date a likely important event 1-2Gyr before the epoch of observation. The emission line galaxies trace a secondary, ongoing infall where groups are accreted along several directions.
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- ID:
- ivo://CDS.VizieR/J/A+A/649/A7
- Title:
- MC structure and properties
- Short Name:
- J/A+A/649/A7
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- This work is part of the Gaia Data Processing and Analysis Consortium papers published with the Gaia Early Data Release 3 (EDR3). It is one of the demonstration papers aiming to highlight the improvements and quality of the newly published data by applying them to a scientific case. We use the Gaia EDR3 data to study the structure and kinematics of the Magellanic Clouds. The large distance to the Clouds is a challenge for the Gaia astrometry. The Clouds lie at the very limits of the usability of the Gaia data, which makes the Clouds an excellent case study for evaluating the quality and properties of the Gaia data. The basis of our work are two samples selected to provide a representation as clean as possible of the stars of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The selection used criteria based on position, parallax, and proper motions to remove foreground contamination from the Milky Way, and allowed the separation of the stars of both Clouds. From these two samples we defined a series of subsamples based on cuts in the colour-magnitude diagram; these subsamples were used to select stars in a common evolutionary phase and can also be used as approximate proxies of a selection by age. We compared the Gaia Data Release 2 (DR2) and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insights into features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones.
- ID:
- ivo://CDS.VizieR/J/AJ/132/2187
- Title:
- MCT1 photometry of NGC 5128 globular clusters
- Short Name:
- J/AJ/132/2187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results from an imaging program with the ACS on the Hubble Space Telescope designed to measure the structural characteristics of a wide range of globular clusters in NGC 5128, the nearest giant elliptical galaxy. From 12 ACS WFC fields we have measured a total of 62 previously known globular clusters and have discovered 69 new high-probability cluster candidates not found in any previous work. We present magnitudes and color indices for all of these, along with rough measurements of their effective diameters and ellipticities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/461/3443
- Title:
- M31 deepest Chandra catalogue of point sources
- Short Name:
- J/MNRAS/461/3443
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study represents the most sensitive Chandra X-ray point source catalogue of M31. Using 133 publicly available Chandra ACIS-I/S observations totalling ~1Ms, we detected 795 X-ray sources in the bulge, north-east, and south-west fields of M31, covering an area of ~=0.6deg^2^, to a limiting unabsorbed 0.5-8.0keV luminosity of ~10^34^erg/s. In the inner bulge, where exposure is approximately constant, X-ray fluxes represent average values because they were determined from many observations over a long period of time. Similarly, our catalogue is more complete in the bulge fields since monitoring allowed more transient sources to be detected. The catalogue was cross-correlated with a previous XMM-Newton catalogue of M31's D_25_ isophote consisting of 1948 X-ray sources, with only 979 within the field of view of our survey. We found 387 (49 per cent) of our Chandra sources (352 or 44 per cent unique sources) matched to within 5 arcsec of 352 XMM-Newton sources. Combining this result with matching done to previous Chandra X-ray sources we detected 259. new sources in our catalogue. We created X-ray luminosity functions (XLFs) in the soft (0.5-2.0keV) and hard (2.0-8.0keV) bands that are the most sensitive for any large galaxy based on our detection limits. Completeness-corrected XLFs show a break around ~=1.3x10^37^erg/s, consistent with previous work. As in past surveys, we find that the bulge XLFs are flatter than the disc, indicating a lack of bright high-mass X-ray binaries in the disc and an aging population of low-mass X-ray binaries in the bulge.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A53
- Title:
- Mean galaxy spectra of the 86 classes
- Short Name:
- J/A+A/649/A53
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Defining templates of galaxy spectra is useful to quickly characterise new obervations and organise data bases from surveys. These templates are usually built from a pre-defined classification based on other criteria. We present an unsupervised classification of 702248 spectra of galaxies and quasars with redshifts smaller than 0.25 that were retrieved from the Sloan Digital Sky Survey (SDSS) database, release 7. The spectra were first corrected for the redshift, then wavelet-filtered to reduce the noise, and finally binned to obtain about 1437 wavelengths per spectrum. Fisher-EM, an unsupervised clustering discriminative latent mixture model algorithm, was applied on these corrected spectra, considering the full set as well as several subsets of 100000 and 300000 spectra. The optimum number of classes given by a penalised likelihood criterion is 86 classes, the 37 most populated ones gathering 99% of the sample. These classes are established from a subset of 302214 spectra. Using several cross-validation techniques we find that this classification is in agreement with the results obtained on the other subsets with an average misclassification error of about 15\%. The large number of very small classes tends to increase this error rate. In this paper, we make a first quick comparison of our classes with the templates of Kennicutt (1992), Dobos et al (2012), Wang et al (2018). This is the first time that an automatic, objective and robust unsupervised classification is established on such a large amount of spectra of galaxies. The mean spectra of the classes can be used as templates for a large majority of galaxies in our Universe.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A118
- Title:
- Mean rest-UV spectra of Ly{alpha} emitters at z>3
- Short Name:
- J/A+A/641/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the ultraviolet (UV) spectral properties of faint Lyman{alpha} emitters (LAEs) in the redshift range 2.9<=z<=4.6 and provide material to prepare future observations of the faint Universe. We use data from the MUSE Hubble Ultra Deep Survey to construct mean rest-frame spectra of continuum-faint (median M_UV_ of -18 and down to M_UV_ of -16), low stellar mass (median value of 10^8.4^ and down to 10^7^ solar masses) LAEs at redshift z>3. We compute various averaged spectra of LAEs sub-sampled on the basis of their observational (e.g., Ly{alpha} strength, UV magnitude and spectral slope) and physical (e.g., stellar mass and star-formation rate) properties. We search for UV spectral features other than Ly{alpha}, such as higher-ionization nebular emission lines and absorption features. We successfully observe the OIII]{lambda}1666 and [CIII]{lambda}1907+CIII]{lambda}1909 collisionally excited emission lines and the HeII{lambda}1640 recombination feature, as well as the resonant CIV{lambda}1548,1551 doublet either in emission or P-Cygni. We compare the observed spectral properties of the different mean spectra and find the emission lines to vary with the observational and physical properties of the LAEs. In particular, the mean spectra of LAEs with larger Ly{alpha} equivalent widths, fainter UV magnitudes, bluer UV spectral slopes and lower stellar masses show the strongest nebular emission. The line ratios of these lines are similar to those measured in the spectra of local metal-poor galaxies, while their equivalent widths are weaker compared to the handful of extreme values detected in individual spectra of z>2 galaxies. This suggests that weak UV features are likely ubiquitous in high z, low-mass and faint LAEs. We publicly release the stacked spectra as they can serve as empirical templates for the design of future observations, such as those with the James Webb Space Telescope and the Extremely Large Telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A88
- Title:
- Measured equivalent widths for Fornax RGB stars
- Short Name:
- J/A+A/572/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fornax is one of the most massive dwarf spheroidal galaxies in the Local Group. The Fornax field star population is dominated by intermediate age stars but star formation was going on over almost its entire history. It has been proposed that Fornax experienced a minor merger event. Despite recent progress, only the high metallicity end of Fornax field stars ([Fe/H]>-1.2dex) has been sampled in larger number via high resolution spectroscopy. We want to better understand the full chemical evolution of this galaxy by better sampling the whole metallicity range, including more metal poor stars. We use the VLT-FLAMES multi-fibre spectrograph in high-resolution mode to determine the abundances of several alpha, iron-peak and neutron-capture elements in a sample of 47 individual Red Giant Branch stars in the Fornax dwarf spheroidal galaxy. We combine these abundances with accurate age estimates derived from the age probability distribution from the colour-magnitude diagram of Fornax. Similar to other dwarf spheroidal galaxies, the old, metal-poor stars of Fornax are typically alpha-rich while the young metal-rich stars are alpha-poor. In the classical scenario of the time delay between Type II (SNe II) and Type Ia Supernovae (SNe Ia), we confirm that SNe Ia started to contribute to the chemical enrichment at [Fe/H] between -2.0 and -1.8dex. We find that the onset of SNe Ia took place between 12-10Gyrs ago. The high values of [Ba/Fe], [La/Fe] reflect the influence of SNe Ia and AGB stars in the abundance pattern of the younger stellar population of Fornax. Our findings of low [alpha/Fe] and enhanced [Eu/Mg] are compatible with an initial mass function that lacks the most massive stars and with star formation that kept going on throughout the whole history of Fornax. We find that massive stars kept enriching the interstellar medium in alpha-elements, although they were not the main contributor to the iron enrichment.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/65
- Title:
- MegaCam survey of outer halo satellites. I.
- Short Name:
- J/ApJ/860/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a deep, systematic imaging study of satellites in the outer halo of the Milky Way. Our sample consists of 58 stellar overdensities --i.e., substructures classified as either globular clusters, classical dwarf galaxies, or ultra-faint dwarf galaxies-that are located at Galactocentric distances of R_GC_>=25kpc (outer halo) and out to ~400kpc. This includes 44 objects for which we have acquired deep, wide-field, g- and r-band imaging with the MegaCam mosaic cameras on the 3.6m Canada-France-Hawaii Telescope and the 6.5m Magellan-Clay telescope. These data are supplemented by archival imaging, or published gr photometry, for an additional 14 objects, most of which were discovered recently in the Dark Energy Survey (DES). We describe the scientific motivation for our survey, including sample selection, observing strategy, data reduction pipeline, calibration procedures, and the depth and precision of the photometry. The typical 5{sigma} point-source limiting magnitudes for our MegaCam imaging-which collectively covers an area of ~52deg^2^ --are g_lim_~25.6 and r_lim_~25.3 AB mag. These limits are comparable to those from the coadded DES images and are roughly a half-magnitude deeper than will be reached in a single visit with the Large Synoptic Survey Telescope. Our photometric catalog thus provides the deepest and most uniform photometric database of Milky Way satellites available for the foreseeable future. In other papers in this series, we have used these data to explore the blue straggler populations in these objects, their density distributions, star formation histories, scaling relations, and possible foreground structures.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/128
- Title:
- Megamaser Cosmology Project. VIII. NGC5765B
- Short Name:
- J/ApJ/817/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Megamaser Cosmology Project, here we present a new geometric distance measurement to the megamaser galaxy NGC 5765b. Through a series of very long baseline interferometry observations, we have confirmed the water masers trace a thin, sub-parsec Keplerian disk around the nucleus, implying an enclosed mass of 4.55+/-0.40x10^7^M_{sun}_. Meanwhile, from single-dish monitoring of the maser spectra over two years, we measured the secular drifts of maser features near the systemic velocity of the galaxy with rates between 0.5 and 1.2km/s/yr. Fitting a warped, thin-disk model to these measurements, we determine a Hubble Constant H_0_ of 66.0+/-6.0km/s/Mpc with an angular-diameter distance to NGC 5765b of 126.3+/-11.6Mpc. Apart from the distance measurement, we also investigate some physical properties related to the maser disk in NGC 5765b. The high-velocity features are spatially distributed into several clumps, which may indicate the existence of a spiral density wave associated with the accretion disk. For the redshifted features, the envelope defined by the peak maser intensities increases with radius. The profile of the systemic masers in NGC 5765b is smooth and shows almost no structural changes over the two years of monitoring time, which differs from the more variable case of NGC 4258.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A147
- Title:
- Megamaser detection in Seyfert galaxies
- Short Name:
- J/A+A/530/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the relation between H_2_O maser detection rate and nuclear obscuration for a sample of 114 Seyfert galaxies, drawn from the CfA, 12um and IRAS F25/F60 catalogs. These sources have mid-infrared spectra from the Spitzer Space Telescope and they are searched for X-ray and [OIII] (5007{AA}) fluxes from the literature. We use the strength of the [OIV] (25.9um) emission line as tracer for the intrinsic AGN strength. After normalization by [OIV] the observed X-ray flux provides information about X-ray absorption. The distribution of X-ray/[OIV] flux ratios is significantly different for masers and non-masers: The maser detected Seyfert-2s (Sy 1.8-2.0) populate a distinct X-ray/[OIV] range which is, on average, about a factor four lower than the range of Seyfert-2 non-masers and about a factor of ten lower than the range of Seyfert-1s (Sy 1.0-1.5). Non-masers are almost equally distributed over the entire X-ray/[OIV] range. This provides evidence that high nuclear obscuration plays a crucial role for the probability of maser detection. Furthermore, after normalization with [OIV], we find a similar but weaker trend for the distribution of the maser detection rate with the absorption of the 7um dust continuum. This suggests that the obscuration of the 7um continuum occurs on larger spatial scales than that of the X-rays. Hence, in the AGN unified model, at moderate deviation from edge-on, the 7um dust absorption may occur without proportionate X-ray absorption. The absorption of [OIII] appears unrelated to maser detections. The failure to detect masers in obscured AGN is most likely due to insufficient observational sensitivity.