- ID:
- ivo://CDS.VizieR/J/A+A/621/A25
- Title:
- Arp 240 Fabry-Perot interferometry
- Short Name:
- J/A+A/621/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Encounters between galaxies modify their morphology, kinematics, and star formation history. The relation between these changes and external perturbations is not straightforward. The great number of parameters involved requires both the study of large samples and individual encounters where particular features, motions, and perturbations can be traced and analysed in detail. We analysed the morphology, kinematics, and dynamics of two luminous infrared spiral galaxies of almost equal mass, NGC 5257 and NGC 5258, in which star formation is mostly confined to the spiral arms, in order to understand interactions between galaxies of equivalent masses and star-forming processes during the encounter. Using scanning Fabry-Perot interferometry, we studied the contribution of circular and non-circular motions and the response of the ionized gas to external perturbations. We compared the kinematics with direct images of the pair and traced the star-forming processes and gravitational effects due to the presence of the other galaxy. The spectral energy distribution of each member of the pair was fitted. A mass model was fitted to the rotation curve of each galaxy. Large, non-circular motions detected in both galaxies are associated with a bar, spiral arms, and HII regions for the inner parts of the galaxies, and with the tidal interaction for the outer parts of the discs. Bifurcations in the rotation curves indicate that the galaxies have recently undergone their pericentric passage. The pattern speed of a perturbation of one of the galaxies is computed. Location of a possible corotation seems to indicate that the gravitational response of the ionized gas in the outer parts of the disc is related to the regions where ongoing star formation is confined. The spectral energy distribution (SED) fit indicates a slightly different star formation history for each member of the pair. For both galaxies, a pseudo-isothermal halo better fits the global mass distribution.
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- ID:
- ivo://CDS.VizieR/J/A+A/631/A94
- Title:
- Avg pitch angles & spiral amplitudes in S4G
- Short Name:
- J/A+A/631/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spiral galaxies are very common in the local Universe, but their formation, evolution, and interplay with bars remain poorly understood after more than a century of astronomical research on the topic. We use a sample of 391 nearby galaxies from the S4G survey to characterise the winding angle and amplitude of spiral arms as a function of disc properties, such as bar strength, in all kinds of spirals (grand-design, multi-armed, and flocculent). We derived global pitch angles in 3.6um de-projected images from i) average measurements of individual logarithmic spiral segments, and ii) for a subsample of 32 galaxies, from 2-D Fourier analyses. The strength of spirals was quantified from the tangential-to-radial force ratio and from the normalised m=2 Fourier density amplitudes. In galaxies with more than one measured logarithmic segment, the spiral pitch angle varies on average by ~10{deg} between segments, but by up to >=15-20{deg}. The distribution of the global pitch angle versus Hubble type (T) is very similar for barred and non-barred galaxies when 1<=T<=5. Most spiral galaxies (>90%) are barred for T>5. The pitch angle is not correlated with bar strength, and only weakly with spiral strength. The amplitude of spirals is correlated with bar strength (and less tightly, with bar length) for all types of spirals. The mean pitch angle is hardly correlated with the mass of the supermassive black hole (estimated from central stellar velocity dispersion), with central stellar mass concentration, or with shear, questioning previous results in the literature using smaller samples. We do not find observational evidence that spiral arms are driven by stellar bars or by invariant manifolds. Most likely, discs that are prone to the development of strong bars are also reactive to the formation of prominent spirals, explaining the observed coupling between bar and spiral amplitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/406/829
- Title:
- Background galaxies in the WSRT wide-field Survey
- Short Name:
- J/A+A/406/829
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Westerbork array to carry out an unbiased wide-field survey for H I emission features, achieving an RMS sensitivity of about 18mJy/beam at a velocity resolution of 17km/s over 1800deg2 and between -1000<VHel<+6500 km/s. The primary data consists of auto-correlation spectra with an effective angular resolution of 49' FWHM. The survey region is centered approximately on the position of Messier 31 and is Nyquist-sampled over 60x30 deg in RAxDec. In this paper we present the results for our HI detections of external galaxies at positive Local Group Standard of Rest (LGSR) velocity. We detect 155 external galaxies in excess of 8 sigma in integrated HI flux density. Plausible optical associations are found within a 30' search radius for all but one of our HI detections in DSS images, although several are not previously catalogued or do not have published redshift determinations. Our detection without a DSS association is at low galactic latitude. Twenty-three of our objects are detected in HI for the first time. We classify almost half of our detections as "confused", since one or more companions is catalogued within a radius of 30' and a velocity interval of 400km/s. Nine of the detected galaxies fall so near the edges of the survey coverage (either spatially or in velocity) that their parameters can not be reliably determined. These nine objects are excluded from the enclosed table.
- ID:
- ivo://CDS.VizieR/J/other/RAA/10.541
- Title:
- Carbon star list (90<l<270, |b|<6)
- Short Name:
- J/other/RAA/10.5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The availability of astrometric data and radial velocities of carbon stars near the Galactic plane enables us to investigate the kinematics of the Milky Way, especially the rotation curve. The recently published Third U.S. Naval Observatory CCD Astrograph Catalog (UCAC3) provides the opportunity to test this problem using three-dimensional velocity in order to obtain more reliable rotation curves. We intend to study the Galactic rotation curve up to 15kpc using the radial velocities and proper motions of carbon stars. The motivation for using UCAC3 is to provide high precision proper motions which have hardly been used in determining the rotation velocity of tracers. Seventy-four carbon stars and carbon-rich Mira variables toward the anti-center direction (90{deg}<l<270{deg}, |b|<6{deg}) are picked up from the literature then matched with UCAC3 carbon star candidates to obtain their proper motions. A rigorous geometrical method is employed to compute the rotation velocity of each object. Taking carbon stars as tracers, we find a flat rotation curve of 210+/-12km/s assuming R0=8.0kpc for the galactocentric distance and V0=220km/s for the rotation velocity of the Sun. Due to the uncertainties of distances, the rotation velocities are more dispersed if tangential velocities enter the calculation, compared to those derived from radial velocities only. However, the whole rotation curve shows coherence with previous results. Increasing observation and study of carbon stars would be desirable in order to provide more homogeneous data for the kinematical study of the Galactic disk.
- ID:
- ivo://CDS.VizieR/J/A+A/634/A10
- Title:
- Chemo-kinematic properties of Aquarius
- Short Name:
- J/A+A/634/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf galaxies found in isolation in the Local Group (LG) are unlikely to have interacted with the large LG spirals, and therefore environmental effects such as tidal and ram-pressure stripping should not be the main drivers of their evolution. We aim to provide insight into the internal mechanisms shaping LG dwarf galaxies by increasing our knowledge of the internal properties of isolated systems. Here we focus on the evolved stellar component of the Aquarius dwarf galaxy, whose kinematic and metallicity properties have only recently started to be explored. Spectroscopic data in the region of the near-infrared Ca~II triplet lines has been obtained with FORS2 at the Very Large Telescope for 53 red giant branch (RGB) stars. These data are used to derive line-of-sight velocities and [Fe/H] of the individual RGB stars. We have derived a systemic velocity of -142.2^+1.8^_-1.8_km/s, in agreement with previous determinations from both the HI gas and stars. The internal kinematics of Aquarius appears to be best modelled by a combination of random motions (l.o.s. velocity dispersion of 10.3^+1.6^_-1.3_km/s) and linear rotation (with a gradient -5.0^+1.6^_-1.9_km/s/arcmin) along a P.A.=139_-27_^+17^deg, broadly consistent with the optical projected major axis. This rotation signal is significantly misaligned or even counter-rotating to that derived from the HI gas. We also find the tentative presence of a mild negative metallicity gradient and indications that the metal-rich stars have a colder velocity dispersion than the metal-poor ones. This work represents a significant improvement with respect to previous measurements of the RGB stars of Aquarius, as it doubles the number of member stars already studied in the literature. We speculate that the misaligned rotation between the HI gas and evolved stellar component might have been the result of recent accretion of HI gas, or re-accretion after gas-loss due to internal stellar feedback.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/31
- Title:
- Dark matter halo models for SPARC galaxies
- Short Name:
- J/ApJS/247/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present rotation curve fits to 175 late-type galaxies from the Spitzer Photometry and Accurate Rotation Curves database using seven dark matter (DM) halo profiles: pseudo-isothermal, Burkert, Navarro-Frenk-White (NFW), Einasto, Di Cintio+ (DC14; 2014MNRAS.441.2986D), cored-NFW, and a new semi-empirical profile named Lucky13. We marginalize over the stellar mass-to-light ratio, galaxy distance, disk inclination, halo concentration, and halo mass (and an additional shape parameter for Einasto) using a Markov Chain Monte Carlo method. We find that cored halo models, such as the DC14 and Burkert profiles, generally provide better fits to rotation curves than the cuspy NFW profile. The stellar mass-halo mass relation from abundance matching is recovered by all halo profiles once imposed as a Bayesian prior, whereas the halo mass-concentration relation is not reproduced in detail by any halo model.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/91
- Title:
- 2D kinematic structure of early-type galaxies
- Short Name:
- J/MNRAS/398/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We detail an innovative new technique for measuring the two-dimensional (2D) velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h3 and h4) of the stellar populations of galaxy haloes using spectra from Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) multi-object spectroscopic observations. The data are used to reconstruct 2D rotation velocity maps. Here we present data for five nearby early-type galaxies to ~three effective radii.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A123
- Title:
- Einasto parameters for SPARC galaxies
- Short Name:
- J/A+A/623/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dark matter-baryon scaling relations in galaxies are important in order to constrain galaxy formation models. Here, we provide a modern quantitative assessment of those relations, by modelling the rotation curves of galaxies from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database with the Einasto dark halo model. We focus in particular on the comparison between the original SPARC parameters, with constant mass-to-light ratios for bulges and disks, and the parameters for which galaxies follow the tightest radial acceleration relation. We show that fits are improved in the second case, and that the pure halo scaling relations also become tighter. We report that the density at the radius where the slope is -2 is strongly anticorrelated to this radius, and to the Einasto index. The latter is close to unity for a large number of galaxies, indicative of large cores. In terms of dark matter-baryon scalings, we focus on relations between the core properties and the extent of the baryonic component, which are relevant to the cusp-core transformation process. We report a positive correlation between the core size of halos with small Einasto index and the stellar disk scale-length, as well as between the averaged dark matter density within 2kpc and the baryon-induced rotational velocity at that radius. This finding is related to the consequence of the radial acceleration relation on the diversity of rotation curve shapes, quantified by the rotational velocity at 2kpc. While a tight radial acceleration relation slightly decreases the observed diversity compared to the original SPARC parameters, the diversity of baryon-induced accelerations at 2kpc is sufficient to induce a large diversity, incompatible with current hydrodynamical simulations of galaxy formation, while maintaining a tight radial acceleration relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1170
- Title:
- Faraday rotation at high Galactic latitude
- Short Name:
- J/ApJ/714/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the vertical magnetic field of the Milky Way toward the Galactic poles, determined from observations of Faraday rotation toward more than 1000 polarized extragalactic radio sources at Galactic latitudes |b|>=77{deg}, using the Westerbork Radio Synthesis Telescope and the Australia Telescope Compact Array. We find median rotation measures (RMs) of 0.0+/-0.5rad/m^2^ and +6.3+/-0.7rad/m^2^ toward the north and south Galactic poles, respectively, demonstrating that there is no coherent vertical magnetic field in the Milky Way at the Sun's position. If this is a global property of the Milky Way's magnetism, then the lack of symmetry across the disk rules out pure dipole or quadrupole geometries for the Galactic magnetic field. The angular fluctuations in RM seen in our data show no preferred scale within the range ~0.1{deg} to ~25{deg}. The observed standard deviation in RM of ~9rad/m^2^ then implies an upper limit of ~1uG on the strength of the random magnetic field in the warm ionized medium at high Galactic latitudes.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/63
- Title:
- Faraday rotation from magnesium II absorbers
- Short Name:
- J/ApJ/795/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong singly ionized magnesium (Mg II) absorption lines in quasar spectra typically serve as a proxy for intervening galaxies along the line of sight. Previous studies have found a correlation between the number of these Mg II absorbers and the Faraday rotation measure (RM) at ~5 GHz. We cross-match a sample of 35752 optically identified non-intrinsic Mg II absorption systems with 25649 polarized background radio sources for which we have measurements of both the spectral index and RM at 1.4 GHz. We use the spectral index to split the resulting sample of 599 sources into flat-spectrum and steep-spectrum subsamples. We find that our flat-spectrum sample shows significant (~3.5{sigma}) evidence for a correlation between Mg II absorption and RM at 1.4 GHz, while our steep-spectrum sample shows no such correlation. We argue that such an effect cannot be explained by either luminosity or other observational effects, by evolution in another confounding variable, by wavelength-dependent polarization structure in an active galactic nucleus, by the Galactic foreground, by cosmological expansion, or by partial coverage models. We conclude that our data are most consistent with intervenors directly contributing to the Faraday rotation along the line of sight, and that the intervening systems must therefore have coherent magnetic fields of substantial strength (B{bar}=1.8+/-0.4{mu}G). Nevertheless, the weak nature of the correlation will require future high-resolution and broadband radio observations in order to place it on a much firmer statistical footing.
