We present a synopsis of the project to establish 32 new faint (16.5 <= V <= 19.8) DA white dwarf (DAWD) spectrophotometric standards distributed over the whole sky. Our results validate the use of fully radiative pure hydrogen model fluxes for hot DA white dwarfs to predict the observed broadband fluxes from near-ultraviolet through the near-infrared to accuracies of a few parts per thousand. After fitting the line of sight reddenings simultaneously with the model spectral energy distributions of these stars against spectroscopic and multiband photometric observations, we have shown that residuals have an rms of typically 0.4%. This indicates that the complications from interstellar dust extinction have been adequately mitigated. Our stars supplement the three brighter DAWDs that define the flux scale of CALSPEC. The consequent photometric accuracy, their all-sky coverage, and their brightness range that matches the dynamic range of large telescopes, constitute an unprecedented ensemble of standard stars for both ground as well as space based use. This paper targets readers who may wish to use these as standard stars and provides them with the essential content to understand their strengths and limitations, without traversing the technical details of analysis that are already captured in a series of papers since 2016. The narrative here describes the motivation, justification, and evolution of the analysis methods; the input data that constrain the modeling; as well as the stability of our results in the face of future improvements in models.

Aims. Supernova remnants (SNRs) are responsible for the injection of energy and chemical elements into the interstellar medium (ISM). The emission from SNRs can be studied to infer information about the supernova (SN) explosion itself as well as about the properties of the surrounding ISM. Studying a sample of SNRs in a galaxy provides an opportunity to better understand stellar feedback, and the best laboratory for such an investigation is the Large Magellanic Cloud (LMC). The LMC is the nearest star-forming galaxy, it lies outside the Galactic plane line of sight, and therefore its foreground absorption is low. Methods. The eROSITA telescopes are the best instruments currently available to perform a survey of the SNRs in the entire LMC due to their large field of view and their high sensitivity towards soft X-rays. We used the sample of SNRs reported in the previous paper and performed a spectral analysis on a part of the sample. We estimated the flux and the luminosity of the fainter sources using the energy conversion factor obtained assuming a non-equilibrium ionisation plasma model. Results. The X-ray luminosity function (XLF) of SNRs in the LMC shows a relatively large number of SNRs at high luminosities. We fitted the distribution with two Gaussian components, which yielded best-fit maxima for the L-X[0.3-8.0keV] distribution at m(1) = 10(34.7 +/- 0.2) erg s(-1) and m(2) = 10(36.5 +/- 0.4) erg s(-1). We compared the XLF of the LMC with the XLFs of the Small Magellanic Cloud (SMC), M31, and M33 using a power-law fit and an Anderson-Darling (DA) test. The power indices of the XLFs of the LMC and SMC appear consistent with each other, while those of M33 and M31 are larger. Thus, the latter have steeper power laws, indicating a lower number of X-ray luminous SNRs with respect to the Magellanic Clouds. The DA test showed that the luminosity distributions of SNRs in the SMC and LMC are compatible with being extracted from the same underlying distribution. They are also compatible for different galaxies if we consider the same lower limit for L-X [0.3-8.0 keV] for the entire distribution. Finally, we compared the luminosity and the X-ray sizes (diameter) of the SNRs in our sample. We observed a general trend of anti-correlation between size and X-ray luminosity that can be interpreted as a result of fading with time.

Aims. Supernova remnants (SNRs) are responsible for the injection of energy and chemical elements into the interstellar medium (ISM). The emission from SNRs can be studied to infer information about the supernova (SN) explosion itself as well as about the properties of the surrounding ISM. Studying a sample of SNRs in a galaxy provides an opportunity to better understand stellar feedback, and the best laboratory for such an investigation is the Large Magellanic Cloud (LMC). The LMC is the nearest star-forming galaxy, it lies outside the Galactic plane line of sight, and therefore its foreground absorption is low. Methods. The eROSITA telescopes are the best instruments currently available to perform a survey of the SNRs in the entire LMC due to their large field of view and their high sensitivity towards soft X-rays. We used the sample of SNRs reported in the previous paper and performed a spectral analysis on a part of the sample. We estimated the flux and the luminosity of the fainter sources using the energy conversion factor obtained assuming a non-equilibrium ionisation plasma model. Results. The X-ray luminosity function (XLF) of SNRs in the LMC shows a relatively large number of SNRs at high luminosities. We fitted the distribution with two Gaussian components, which yielded best-fit maxima for the LX[0.3-8.0keV] distribution at m1 = 1034.7±0.2 erg s−1 and m2 = 1036.5±0.4 erg s−1. We compared the XLF of the LMC with the XLFs of the Small Magellanic Cloud (SMC), M31, and M33 using a power-law fit and an Anderson-Darling (DA) test. The power indices of the XLFs of the LMC and SMC appear consistent with each other, while those of M33 and M31 are larger. Thus, the latter have steeper power laws, indicating a lower number of X-ray luminous SNRs with respect to the Magellanic Clouds. The DA test showed that the luminosity distributions of SNRs in the SMC and LMC are compatible with being extracted from the same underlying distribution. They are also compatible for different galaxies if we consider the same lower limit for LX [0.3-8.0 keV] for the entire distribution. Finally, we compared the luminosity and the X-ray sizes (diameter) of the SNRs in our sample. We observed a general trend of anti-correlation between size and X-ray luminosity that can be interpreted as a result of fading with time.

Context. The Large Magellanic Cloud (LMC), being a nearby and actively star-forming satellite galaxy of the Milky Way, is an ideal site to observe the multiphase interstellar medium (ISM) of a galaxy across the electromagnetic spectrum. Aims. We aimed to exploit the available SRG/eROSITA all-sky survey data to study the distribution, composition and properties of the diffuse X-ray emitting hot gas in the LMC. Methods. We constructed multiband X-ray images of the LMC, reflecting the morphology and temperatures of the diffuse hot gas. By performing spatially resolved X-ray spectroscopy of 175 independent regions, we constrained the distribution, temperature, mass, energetics and composition of the hot ISM phase throughout the galaxy, while also testing for the presence of X-ray synchrotron emission. We combined our constraints with multiwavelength data to obtain a comprehensive view of the different ISM phases. Results. We measure a total X-ray luminosity of the hot ISM phase of 1.9 x 10(38) erg s(-1) (0.2-5.0 keV band), and constrain its thermal energy to around 9 x 10(54) erg. The typical density and temperature of the X-ray emitting plasma are around 5 x 10(-3) cm(-3) and 0.25 keV, respectively, with both exhibiting broad peaks in the southeast of the LMC. The observed degree of X-ray absorption correlates strongly with the distribution of foreground H I gas, whereas a spatial anticorrelation between the hot and cold ISM phases is visible on sub-kpc scales within the disk. The abundances of light metals show a strong gradient throughout the LMC, with the north and east exhibiting a strong alpha-enhancement, as expected from observed massive stellar populations there. In contrast, the enigmatic "X-ray spur" exhibits a local deficit in alpha-elements, and a peak in hot-gas pressure at P/k similar to 10(5) K cm(-3), consistent with a dominant energy input through tidally driven gas collisions. Finally, we tentatively identify spectroscopic signatures of nonthermal X-ray emission from the supergiant shell LMC 2, although contamination by straylight cannot be excluded.

When a star dies, it can explode in a supernova, causing a strong shock wave and forming an interstellar object called a supernova remnant (SNR). Observational studies of SNRs allow us to learn about the different types of progenitors, the explosion mechanisms, the physics of interstellar shocks, and the matter cycle in galaxies. We report on the first detection of SNRs located on the outskirts of a galaxy; namely, the Large Magellanic Cloud (LMC), the largest satellite galaxy of our Galaxy. The sources were discovered similar to 3 degrees outside the main stellar and gas distribution of the LMC in the recent surveys in radio with the Australian Square Kilometre Array Pathfinder (ASKAP) and in X-rays with the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). We studied them in follow-up observations with the X-ray Multi-Mirror Mission-Newton telescope and MeerKAT and confirmed them to be SNRs. Their progenitors are most likely stars that had left the LMC due to tidal interaction between the Magellanic Clouds and the Milky Way. SNR J0614-7251 is located in an environment with a similar density to those of the other known SNRs in the LMC, and has similar X-ray properties. SNR J0624-6948, on the other hand, is located in a region with a lower density, n(0) < 0.01 cm(-3). Its radio shell shows a spectral index and polarisation typical of an SNR.

We have used the Dark Energy Camera (DECam) on the CTIO Blanco 4 m telescope to perform a new emission-line survey of the Large Magellanic Cloud (LMC) using narrowband H alpha and [S ii] filters in addition to a continuum band to create pure emission-line images. We refer to this new survey as DeMCELS, to distinguish it from the earlier Magellanic Cloud Emission-line Survey (MCELS). DeMCELS covers similar to 54 deg2, encompassing most of the bright optical disk of the LMC. With DECam's pixel size of only 0.'' 27, our DeMCELS survey provides a seeing-limited improvement of 3-5 times over MCELS and is comparable in depth, with surface brightness limits of 3.3x10-17ergcm-2s-1arcsec-2 and 2.9x10-17ergcm-2s-1arcsec-2 in H alpha and [S ii], respectively. DeMCELS provides detailed morphological information on nebulae of all scales, from the largest supershells to individual H ii regions and supernova remnants, to bubbles of emission surrounding individual stars, and even to faint structures in the diffuse ionized gas of the LMC. Many complex regions of emission show significant variations in the ratio of [S ii] to H alpha-a sign of a mixture of shocks from stellar winds and/or supernovae with photoionization by embedded hot, young stars. We present the details of the observing strategy and data processing for this survey, and show selected results in comparison with previous data. A companion project for the Small Magellanic Cloud is in progress and will be reported separately. We are making these new data available to the community at large via NOIRLab's Data Lab site.

Aims. The all-sky survey carried out by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board Spektrum-Roentgen-Gamma (Spektr-RG, SRG) has provided spatially and spectrally resolved X-ray data of the entire Large Magellanic Cloud (LMC) and its immediate surroundings in the soft X-ray band down to 0.2 keV, with an average angular resolution of 26 '' in the field of view. In this work, we study the supernova remnants (SNRs) and SNR candidates in the LMC using data from the first four all-sky surveys (eRASS:4). From the X-ray data, in combination with results at other wavelengths, we obtain information about the SNRs, their progenitors, and the surrounding interstellar medium (ISM). Studying the entire population of SNRs in a galaxy aids in understanding the underlying stellar populations, the environments in which the SNRs are evolving, and the stellar feedback on the ISM. Methods. The eROSITA telescopes are the best instruments currently available for the study of extended soft sources such as SNRs in an entire galaxy due to their large field of view and high sensitivity in the softer part of the X-ray band. We applied the Gaussian gradient magnitude filter to the eROSITA images of the LMC in order to highlight the edges of the shocked gas and find new SNRs. We visually compared the X-ray images with those of their optical and radio counterparts to investigate the true nature of the extended emission. The X-ray emission was evaluated using the contours with respect to the background, while for the optical, we used line ratio diagnostics and non-thermal emission in the radio images. We used the Magellanic Cloud Emission Line Survey for the optical data. For the radio comparison, we used data from the Australian Square Kilometre Array Pathfinder survey of the LMC. Using the star formation history derived from the near-IR photometry of the VISTA survey of the Magellanic Clouds, we investigated the possible progenitor type of the new SNRs and SNR candidates in our sample. Results. We present the most up-to-date catalogue of SNRs in the LMC. Previously known SNRs and SNR candidates were detected with a 1 sigma significance down to a surface brightness of Sigma [0.2-5.0 keV] = 3.0 x 10(-15) erg s(-1) cm(-2) arcmin(-2) and were examined. The eROSITA data allowed us to confirm one of the previous candidates as an SNR. We confirm three newly detected extended sources as new SNRs, while we propose 13 extended sources as new X-ray SNR candidates. We also present the analysis of the follow-up XMM-Newton observation of MCSNR J0456-6533 discovered with eROSITA. Among the new candidates, we propose J0614-7251 (4eRASSU J061438.1-725112) as the first X-ray SNR candidate in the outskirts of the LMC.

Auxiliary data files for Axelrod et al. 2023 (in prep.). "HST_passbands" - Hubble Space Telescope photometric filter passthroughs. First column is vacuum wavelength in nm, second column is response. "SED" - calibrated spectral flux density distributions. First column is vacuum wavelength in Angstrom, second column is SED in erg/sec/cm**2/Angstrom. "Tables" - paper tables in LaTeX.

Hot DA white dwarfs have fully radiative pure hydrogen atmospheres that are the least complicated to model. Pulsationally stable, they are fully characterized by their effective temperature Teff, and surface gravity log g, which can be deduced from their optical spectra and used in model atmospheres to predict their spectral energy distribution (SED). Based on this, three bright DAWDs have defined the spectrophotometric flux scale of the CALSPEC system of HST. In this paper we add 32 new fainter (16.5 < V < 19.5) DAWDs spread over the whole sky and within the dynamic range of large telescopes. Using ground based spectra and panchromatic photometry with HST/WFC3, a new hierarchical analysis process demonstrates consistency between model and observed fluxes above the terrestrial atmosphere to < 0.004 mag rms from 2700 Å to 7750 Å and to 0.008 mag rms at 1.6μm for the total set of 35 DAWDs. These DAWDs are thus established as spectrophotometric standards with unprecedented accuracy from the near ultraviolet to the near-infrared, suitable for both ground and space based observatories. They are embedded in existing surveys like SDSS, PanSTARRS and GAIA, and will be naturally included in the LSST survey by Rubin Observatory. With additional data and analysis to extend the validity of their SEDs further into the IR, these spectrophotometric standard stars could be used for JWST, as well as for the Roman and Euclid observatories.

We describe radio, optical, and X-ray observations of this rather faint, old Large Magellanic Cloud (LMC) supernova remnant. The [O iii ] emission forms a distinct shell, the remnant of the outer shock, which encloses the radio and X-ray emission and gives an estimate of age and explosion energy. Because of a collision with an LMC H α filament, radio and X-ray emission are concentrated in the northern half of the remnant. The X-ray spectrum is well fit assuming the plasma is isothermal and in collisional equilibrium. The best-fit temperature is such that almost all energy is in lines from O, Ne, Mg, and Fe. The known distance, low extinction, and low interstellarmedium metallicity allow derivation of masses of several elements produced by the star and in the explosion. The masses of O, Ne, and Fe point to a Type II supernova from the explosion of a 20–25 M _⊙ star. The mass of Mg, however, is higher than that of almost all predictions, but some of this apparent excess might be due to a higher-temperature region in the X-ray-emitting material. Point-like background sources are examined to search for a neutron star, and one possible candidate is found just inside the shell of the remnant.

In the first months after the launch in July 2019, eROSITA onboard Spektr-RG (SRG) performed long-exposure observations in the regions around SN 1987A and SNR N132D in the Large Magellanic Cloud (LMC). We analyse the distribution and the spectrum of the diffuse X-ray emission in the observed fields to determine the physical properties of the hot phase of the interstellar medium (ISM). The eROSITA data are complemented by newly derived column density maps for the Milky Way and the LMC, 888 MHz radio continuum map from the Australian Square Kilometer Array Pathfinder (ASKAP), and optical images of the Magellanic Cloud Emission Line Survey (MCELS). We detect significant emission from thermal plasma with kT=0.2 keV in all the regions. There is also an additional higher-temperature emission component from a plasma with kT = 0.7 keV. In addition, non-thermal X-ray emission is significantly detected in the superbubble 30 Dor C. The absorbing column density NH in the LMC derived from the analysis of the X-ray spectra taken with eROSITA is consistent with the NH obtained from the emission of the cold medium over the entire area. Neon abundance is enhanced in the regions in and around 30 Dor and SN 1987A, indicating that the ISM has been chemically enriched by the young stellar population. Emission from the stellar cluster RMC 136 and the Wolf-Rayet stars RMC 139 and RMC 140 is best modelled with a high-temperature (kT>1 keV) non-equilibrium ionisation plasma emission and a non-thermal component with a photon index of {\Gamma} =1.3. In addition, the optical SNR candidate J0529-7004 is also detected with eROSITA and we thus confirm the source as an SNR.

P. J. Kavanagh,1†M. Sasaki,2 M. D. Filipović,3 S. D. Points,4 L. M. Bozzetto,3 F. Haberl,6 P. Maggi,5 C. Maitra6 1School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwillam Place, Dublin 2, Ireland 2Dr Karl Remeis Observatory and ECAP, Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany 3Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia 4NSF’s NOIRLab/CTIO, Casilla 603, La Serena, Chile 5Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg, France 6Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, D-85748 Garching, Germany

We verified for photometric stability a set of DA white dwarfs with Hubble Space Telescope magnitudes from the near-ultraviolet to the near-infrared and ground-based spectroscopy by using time-spaced observations from the Las Cumbres Observatory network of telescopes. The initial list of 38 stars was whittled to 32 final ones which comprise a high quality set of spectrophotometric standards. These stars are homogeneously distributed around the sky and are all fainter than r 16.5 mag. Their distribution is such that at least two of them would be available to be observed from any observatory on the ground at any time at airmass less than two. Light curves and different variability indices from the Las Cumbres Observatory data were used to determine the stability of the candidate standards. When available, Pan-STARRS1, Zwicky Transient Facility and TESS data were also used to confirm the star classification. Our analysis showed that four DA white dwarfs may exhibit evidence of photometric variability, while a fifth is cooler than our established lower temperature limit, and a sixth star might be a binary. In some instances, due to the presence of faint nearby red sources, care should be used when observing a few of the spectrophotometric standards with ground-based telescopes. Light curves and finding charts for all the stars are provided.

We present a new optical sample of three Supernova Remnants (SNRs) and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud (LMC). These objects were originally selected using deep H alpha, [S II], and [O III] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC's main body. Together with previously suggested MCSNR J0541-6659, we confirm the SNR nature for two additional new objects: MCSNR J0522-6740 and MCSNR J0542-7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [S II]/H alpha emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509-6402 to be a special example of the remnant of a possible type Ia Supernova (SN) which is situated some 2 degrees (similar to 1.75 kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of similar to 2. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.

The Large Magellanic Cloud supernova remnant J0454-6713 abutting the H ii region N9 has been observed with XMM-Newton. Two groups of lines from Fe xvii account for half the emission and lines from Fe xviii , O vii , and O viii are also clearly detected with the XMM RGS. Isothermal equilibrium fits of the EPIC spectra reproduce the basic spectral form and show little variation throughout the remnant but are insensitive to the lines from the high-temperature ions. These are overwhelmed in the EPIC cameras by the dominant Fe xvii radiation and the EPIC best-fit spectra do not agree with the RGS data. Uncertainties in the atomic data used to determine Fe-line strength present a further complication which inhibits a good EPIC spectral fit. We build a two-temperature model which does fit both RGS and EPIC results and propose that the high-T component is from SN debris and the low from heated material in the H ii region. The high ratio of Fe emission to that from O requires the remnant to be the product of a Type Ia supernova and points to a deflagration–detonation origin. Weak X-ray emission from the N9 superbubble is detected and briefly discussed. The abundance of Ne in N9 material seems higher than average for the LMC in both the superbubble spectrum and the low-temperature component of the remnant RGS spectrum.

Aims. We develop an automatic bubble-recognition routine based on Minkowski functionals (MF) and tensors (MT) to detect bubble-like interstellar structures in optical emission line images. Methods. Minkowski functionals and MT are powerful mathematical tools for parameterizing the shapes of bodies. Using the papaya2-library, we created maps of the desired MF or MT of structures at a given window size. We used maps of the irreducible MT ψ2, which is sensitive to elongation, to find filamentary regions in Hα, [S II], and [O III] images of the Magellanic Cloud Emission Line Survey. Using the phase of ψ2, we were able to draw lines perpendicular to each filament and thus obtain line-density maps. This allowed us to find the center of a bubble-like structure and to detect structures at different window sizes. Results. The detected bubbles in all bands are spatially correlated to the distribution of massive stars, showing that we indeed detect interstellar bubbles without large spatial bias. Eighteen out of 59 supernova remnants in the Large Magellanic Cloud (LMC) and 13 out of 20 superbubbles are detected in at least one wavelength. The lack of detection is mostly due to surrounding emission that disturbs the detection, a too small size, or the lack of a (circular) counterpart in our emission line images. In line-density maps at larger scales, maxima can be found in regions with high star formation in the past, often inside supergiant shells (SGS). In SGS LMC 2, there is a maximum west of the shell where a collision of large gas clouds is thought to have occurred. In the Small Magellanic Cloud (SMC), bubble detection is impaired by the more complex projected structure of the galaxy. Line maps at large scales show large filaments in the SMC in a north-south direction, especially in the [S II] image. The origin of these filaments is unknown.

We have made a spectroscopic investigation of the nature of 053949.17-693747.4, a blue star with mid-infrared excess, projected within a superbubble in the Hiicomplex N160 in the Large Magellanic Cloud (LMC). Analyses of photometric and spectrophotometric data of this star indicate that it is an O7 1 V in the LMC. The radial velocity of this star from a 2010 spectrum shows an offset of similar to 150 km s(-1)from that of the background interstellar medium (ISM), while the spectra taken in 2020 show stellar velocity similar to the ISM velocity. The velocity variations indicate that 053949.17-693747.4 must be a binary system. The lack of spectroscopic features from a stellar companion and the large radial velocity variations of the primary O7 star imply that the companion is most likely an early-type B star. Hubble Space Telescope H alpha and [Oiii] images of 053949.17-693747.4 show a small nebula around the star with the southern rim resembling a blow-shock-like structure. While the physical nature as a bow shock cannot be robustly established, this small nebula is likely the cause of 053949.17-693747.4's mid-infrared excess. Spectroscopic monitoring over an entire binary period is needed to establish the period and systemic velocity to determine the properties of the binary companion and whether this binary system is a runaway.

We describe the design and implementation of a fourth version of the TripleSpec near-infrared spectrograph (TSpec4). This version of the instrument was designed for and first implemented on the 4-m Blanco telescope on Cerro Tololo, and subsequently converted for use on the 4-m Southern Astrophysical Research (SOAR) Telescope on Cerro Pachon. Details of the changed opto-mechanical design and mounting arrangements are discussed. An updated data pipeline provides reduced spectra from the instrument. We describe the required modifications and the performance of both implementations of TSpec4.The move from the Blanco to SOAR required changing from operation at a classical Cassegrain f/8 focus to operation at a Nasmyth f/16 focus. The SOAR mount also employs a rotator and required accommodation to a significantly different back-focal distance inside the instrument. These changes were implemented by modifying the instrument fore-optics which feeds light onto the slit at f/10.6. The spectrograph and slit viewer optics are unchanged. A dichroic reflects infrared light toward the instrument while passing visible light to a SOAR facility guider; this removes the shortest wavelengths from the spectra and in turn required modification of the data reduction pipeline.As the telescopes have similar apertures, the performance of the instrument is similar on both, though on SOAR image quality is somewhat better and details of the instrument’s optical properties differ also. Flexure performance differs as well due to the different instrument locations.

Many more supernova remnants (SNRs) are now known in external galaxies than in the Milky Way. Most of these SNRs have been identified using narrowband imaging, separating SNRs from H ii regions on the basis of [S ii ]:H α ratios that are elevated compared to H ii regions. However, the boundary between SNRs and H ii regions is not always distinct, especially at low surface brightness. Here we explore velocity structure as a possible criterion for separating SNRs from H ii regions, using a sample of well-studied SNRs in the Large Magellanic Cloud as well as a small number of SNRs in the galaxy M83. We find, perhaps not surprisingly, that even at large diameters, SNRs exhibit velocity broadening sufficient to readily distinguish them from H ii regions. We thus suggest that the purity of most extragalactic samples would be greatly improved through spectroscopic observations with a velocity resolution of order 50 km s −1 .