- ID:
- ivo://CDS.VizieR/J/A+A/641/A95
- Title:
- NGC 4104 g and r CFHT/Megacam images
- Short Name:
- J/A+A/641/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Groups are the most common association of galaxies in the Universe and they are found in different configuration states, such as loose, compact, and fossil groups. We studied the galaxy group MKW 4s, dominated by the giant early-type galaxy NGC 4104 at z=0.0282, with the aim of understanding the evolutionary stage of this group and to place it within the framework of the standard {Lambda}CDM cosmological scenario. We obtained deep optical data with CFHT/Megacam (g and r bands) and we applied both the galfit 2D image fitting program and the IRAF/ellipse 1D radial method to model the brightest group galaxy (BGG) and its extended stellar envelope. We also analysed the publicly available XMM-Newton and Chandra X-ray data. From N-body simulations of dry-mergers with different mass ratios of the infalling galaxy, we were able to constrain the dynamical stage of this system. Our results show a stellar shell system feature in NGC 4104 and an extended envelope that was reproduced by our numerical simulations of a collision with a satellite galaxy taking place about 4-6Gyr ago. The initial pair of galaxies had a mass ratio of at least 1:3. Taking into account the stellar envelope contribution to the total r band magnitude and the X-ray luminosity, MKW 4s falls into the category of a fossil group. Our results show that we are witnessing a rare case of a shell elliptical galaxy in a forming fossil group.
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- ID:
- ivo://CDS.VizieR/J/A+A/654/A40
- Title:
- NGC1042 g and r deep final images
- Short Name:
- J/A+A/654/A40
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the first results of the LBT Imaging of Galaxy Haloes and Tidal Structures (LIGHTS) survey. LIGHTS is an ongoing observational campaign with the 2x8.4m Large Binocular Telescope (LBT) aiming to explore the stellar haloes and the low surface brightness population of satellites down to a depth of mu_V_~31mag/arcsec^2^ (3s in 10"x10" boxes) of nearby galaxies. We simultaneously collected deep imaging in the g and r Sloan filters using the Large Binocular Cameras (LBCs). The resulting images are 60 times (i.e. 4.5mag) deeper than those from the Sloan Digital Sky Survey (SDSS), and they have characteristics comparable (in depth and spatial resolution) to the ones expected from the future Legacy Survey of Space and Time (LSST). Here we show the first results of our pilot programme targeting NGC1042 (an M33 analogue at a distance of 13.5Mpc) and its surroundings. The depth of the images allowed us to detect an asymmetric stellar halo in the outskirts of this galaxy whose mass (1.4+/-0.4x10^8^M_{sun}_) is in agreement with the Lambda Cold Dark Matter (LambdaCDM) expectations. Additionally, we show that deep imaging from the LBT reveals low mass satellites (a few times 10^5^M_{sun}_) with very faint central surface brightness mu_V(0)_~27mag/arcsec^2^(i.e. similar to Local Group dwarf spheroidals, such as Andromeda XIV or Sextans, but at distances well beyond the local volume). The depth and spatial resolution provided by the LIGHTS survey open up a unique opportunity to explore the `missing satellites' problem in a large variety of galaxies beyond our Local Group down to masses where the difference between the theory and observation (if any) should be significant.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A45
- Title:
- NGC4330 GHASP and PUMA datacubes
- Short Name:
- J/A+A/659/A45
- Date:
- 04 Mar 2022 00:48:25
- Publisher:
- CDS
- Description:
- Using the VESTIGE survey, a deep narrow-band H{alpha} imaging survey of the Virgo cluster carried on at the CFHT with MegaCam, we have discovered a long and diffuse tail of ionised gas in the edge-on late-type galaxy NGC4330. This peculiar feature witnesses an ongoing ram pressure stripping event able to remove the gas in the outer region of the disc. Tuned hydrodynamic simulations suggest that the ram pressure stripping event is occurring almost face-on, making NGC4330 the ideal candidate to study the effects of the perturbation in the direction perpendicular to the disc plane. We present here two new independent sets of Fabry-Perot observations (R~10000) with the purpose of understanding the effects of ram pressure stripping process on the kinematics of the ionised gas. Despite their limited sensitivity to the diffuse gas emission, the data allowed us to measure the velocity and the velocity dispersion fields over the galaxy disc and in several features at the edges or outside the stellar disc formed after the ram pressure stripping event. We have constructed the position-velocity diagrams and the rotation curves of the galaxy using three different techniques. The data show, consistent with the hydrodynamic simulations, that the galaxy has an inner solid-body rotation up to ~2.4kpc, with noncircular streaming motions outwards the disc and in the several external features formed during the interaction of the galaxy with the surrounding intracluster medium. The data also indicate a decrease of the rotational velocity of the gas with increasing distance from the galaxy disc along the tails, suggesting a gradual but not linear loss of angular momentum in the stripped gas. Consistent with a ram pressure stripping scenario, the i-band image shows a boxy shape at the southwest edge of the disc, where the stellar orbits might have been perturbed by the modification of the gravitational potential well of the galaxy due to the displacement of the gas in the z-direction.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A6
- Title:
- NGC628 3.1GHz total intensity & polarised images
- Short Name:
- J/A+A/600/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields are essential to fully understand the interstellar medium (ISM) and its role in the disk-halo interface of galaxies is still poorly understood. Star formation is known to expel hot gas vertically into the halo and these outflows have important consequences for mean-field dynamo theory in that they can be efficient in removing magnetic helicity. We perform new observations of the nearby face-on spiral galaxy NGC 628 with the Karl G. Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at frequencies of 2.6GHz and 8.35GHz. We obtain some of the most sensitive radio continuum images in both total and linearly polarised intensity of any external galaxy observed so far in addition to high-quality images of Faraday depth and polarisation angle from which we obtained evidence for drivers of magnetic turbulence in the disk-halo connection. Such drivers include a superbubble detected via a significant Faraday depth gradient coinciding with a HI hole. We observe an azimuthal periodic pattern in Faraday depth with a pattern wavelength of 3.7+/-0.1kpc, indicating Parker instabilities. The lack of a significant anti-correlation between Faraday depth and magnetic pitch angle indicates that these loops are vertical in nature with little helical twisting, unlike in IC 342. We find that the magnetic pitch angle is systematically larger than the morphological pitch angle of the polarisation arms which gives evidence for the action of a large-scale dynamo where the regular magnetic field is not coupled to the gas flow and obtains a significant radial component. We additionally discover a lone region of ordered magnetic field to the north of the galaxy with a high degree of polarisation and a small pitch angle, a feature that has not been observed in any other galaxy so far and is possibly caused by an asymmetric HI hole.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/75
- Title:
- NGC 5824 giant star members from VLT obs.
- Short Name:
- J/ApJ/859/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 5824 is a massive Galactic globular cluster suspected to have an intrinsic spread in its iron content, according to the strength of the calcium triplet lines. We present chemical abundances of 117 cluster giant stars using high-resolution spectra acquired with the multi-object spectrograph FLAMES. The metallicity distribution of 87 red giant branch stars is peaked at [Fe/H]=-2.11+/-0.01dex, while that derived from 30 asymptotic giant branch stars is peaked at [Fe/H]=-2.20+/-0.01dex. Both the distributions are compatible with a null spread, indicating that this cluster did not retain the ejecta of supernovae. The small iron abundance offset between the two groups of stars is similar to the abundances already observed among red and asymptotic giant branch stars in other clusters. The lack of intrinsic iron spread rules out the possibility that NGC 5824 is the remnant of a disrupted dwarf galaxy, as previously suggested. We also find evidence of the chemical anomalies usually observed in globular clusters, namely the Na-O and the Mg-Al anticorrelations. In particular, NGC 5824 exhibits a huge range of [Mg/Fe] abundance, observed in only a few metal-poor and/or massive clusters. We conclude that NGC 5824 is a normal globular cluster, without spread in [Fe/H] but with an unusually large spread in [Mg/Fe], possibly due to an efficient self-enrichment driven by massive asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/420/37
- Title:
- NGC 4365 globular clusters
- Short Name:
- J/MNRAS/420/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Analysis of the globular cluster (GC) system of the giant elliptical (E3) galaxy NGC 4365, from eight Hubble Space Telescope/Advanced Camera for Surveys pointings and a wide-field Subaru/Suprime-Cam image, is presented. Using magnitude, colour and size criteria, we obtain a catalogue of GC candidates. We also measure the photometric properties of the galaxy starlight, including a new measure of the effective radius.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/1485
- Title:
- NGC 3923 globular clusters
- Short Name:
- J/MNRAS/421/1485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents further results from our spectroscopic study of the globular cluster (GC) system of the group elliptical NGC 3923. From observations made with the GMOS instrument on the Gemini South Telescope, an additional 50 GC and ultra-compact dwarf (UCD) candidates have been spectroscopically confirmed as members of the NGC 3923 system. When the recessional velocities of these GCs are combined with the 29 GC velocities reported previously, a total sample of 79 GC/UCD velocities is produced. This sample extends to over 6-arcmin (>6Re~30kpc) from the centre of NGC 3923 and is used to study the dynamics of the GC system and the dark matter content of NGC 3923.
- ID:
- ivo://CDS.VizieR/J/ApJ/705/1533
- Title:
- NGC 5128 globular clusters
- Short Name:
- J/ApJ/705/1533
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An objective classification of the globular clusters (GCs) of NGC 5128 has been carried out by using a model-based approach of cluster analysis. The set of observable parameters includes structural parameters, spectroscopically determined Lick indices and radial velocities from the literature. The optimum set of parameters for this type of analysis is selected through a modified technique of principal component analysis, which differs from the classical one in the sense that it takes into consideration the effects of outliers present in the data. Then a mixture model based approach has been used to classify the GCs into groups. The efficiency of the techniques used is tested through the comparison of the misclassification probabilities with those obtained using the K-means clustering technique. On the basis of the above classification scheme three coherent groups of GCs have been found. We propose that the clusters of one group originated in the original cluster formation event that coincided with the formation of the elliptical galaxy, and that the clusters of the two other groups are of external origin, from tidally stripped dwarf galaxies on random orbits around NGC 5128 for one group, and from an accreted spiral galaxy for the other.
- ID:
- ivo://CDS.VizieR/J/AJ/140/2101
- Title:
- NGC 5128 globular clusters photometry
- Short Name:
- J/AJ/140/2101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometry for 323 of the globular clusters in NGC 5128 (Centaurus A), measured for the first time in the g'r'i'z' filter system. The color indices are calibrated directly to standard stars in the g'r'i'z' system and are used to establish the fiducial mean colors for the blue and red (low and high metallicity) globular cluster sequences. We also use previously published spectroscopically measured abundances to establish the conversion between the most metallicity-sensitive colors ((g'-r')_0_,(g'-i')_0_) and metallicity, [Fe/H].
- ID:
- ivo://CDS.VizieR/J/AJ/134/494
- Title:
- NGC 5128 globular clusters UBVRICMT1 phot. & RV
- Short Name:
- J/AJ/134/494
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new kinematic and dynamic study of the halo of the giant elliptical galaxy NGC 5128 is presented. From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae, the rotation amplitude, rotation axis, velocity dispersion, and total dynamical mass are determined for the halo of NGC 5128.
