- ID:
- ivo://CDS.VizieR/J/AJ/160/199
- Title:
- Estimated distances for ~12000 galaxies with NED-D
- Short Name:
- J/AJ/160/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Numerous research topics rely on an improved cosmic distance scale (e.g., cosmology, gravitational waves) and the NASA/IPAC Extragalactic Database of Distances (NED-D) supports those efforts by tabulating multiple redshift-independent distances for 12000 galaxies (e.g., Large Magellanic Cloud (LMC) zero-point). Six methods for securing a mean estimate distance (MED) from the data are presented (e.g., indicator and Decision Tree). All six MEDs yield surprisingly consistent distances for the cases examined, including for the key benchmark LMC and M106 galaxies. The results underscore the utility of the NED-D MEDs in bolstering the cosmic distance scale and facilitating the identification of systematic trends.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/432/2112
- Title:
- Estimating gas masses from HI and CO data
- Short Name:
- J/MNRAS/432/2112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method to estimate the total gas column density, dust-to-gas and dust-to-metal ratios of distant galaxies from rest-frame optical spectra. The technique exploits the sensitivity of certain optical lines to changes in depletion of metals on to dust grains and uses photoionization models to constrain these physical ratios along with the metallicity and dust column density. We compare our gas column density estimates with HI and CO gas mass estimates in nearby galaxies to show that we recover their total gas mass surface density to within a factor of 2 up to a total surface gas mass density of ~75M{sun}/pc^2^. Our technique is independent of the conversion factor of CO to H_2_ and we show that a metallicity-dependent X_CO_ is required to achieve good agreement between our measurements and that provided by CO and HI. However, we also show that our method cannot be reliably aperture corrected to total integrated gas mass. We calculate dust-to-gas ratios for all star-forming galaxies in the Sloan Digital Sky Survey Data Release 7 and show that the resulting dependence on metallicity agrees well with the trend inferred from modelling of the dust emission of nearby galaxies using far-IR data. We also present estimates of the variation of the dust-to-metal ratio with metallicity and show that this is poorly constrained at metallicities below 50% solar. We conclude with a study of the inventory of gas in the central regions, defined both in terms of a fixed physical radius and as a fixed fraction of the half-light radius, of ~70000 star-forming galaxies from the Sloan Digital Sky Survey. We show that their central gas content and gas depletion time are not accurately predicted by a single parameter, but in agreement with recent studies we find that a combination of the stellar mass and some measure of central concentration provides a good predictor of gas content in galaxies. We also identify a population of galaxies with low surface densities of stars and very long gas depletion times.
- ID:
- ivo://CDS.VizieR/J/AJ/117/981
- Title:
- Estimation of stellar metal abundance. II.
- Short Name:
- J/AJ/117/981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have recalibrated a method for the estimation of stellar metal abundance, parameterized as [Fe/H], based on medium-resolution (1-2{AA}) optical spectra (the majority of which cover the wavelength range 3700-4500{AA}). The equivalent width of the Ca II K line (3933{AA}) as a function of [Fe/H] and broadband B-V color, as predicted from spectrum synthesis and model atmosphere calculations, is compared with observations of 551 stars with high-resolution abundances available from the literature (a sevenfold increase in the number of calibration stars that were previously available). A second method, based on the Fourier autocorrelation function technique first described by Ratnatunga & Freeman (1989, Cat. <V/65>), is used to provide an independent estimate of [Fe/H], as calibrated by comparison with 405 standard-star abundances.
- ID:
- ivo://CDS.VizieR/J/A+A/540/A133
- Title:
- {eta} Car emission spectrum (1700-10400{AA})
- Short Name:
- J/A+A/540/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present line identifications in the 1700 to 10400{AA} region for the Weigelt blobs B and D, located 0.1" to 0.3" NNW of {eta} Carinae. The aim of this work is to characterize the behavior of these luminous, dense gas blobs in response to the broad high-state and the short low-state of {eta} Carinae during its 5.54-year spectroscopic period.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/45
- Title:
- eta Carinae obs. around the 2014 X-ray minimum
- Short Name:
- J/ApJ/838/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on Swift X-ray Telescope observations of Eta Carinae ({eta}Car), an extremely massive, long-period, highly eccentric binary obtained during the 2014.6 X-ray minimum/periastron passage. These observations show that {eta} Car may have been particularly bright in X-rays going into the X-ray minimum state, while the duration of the 2014 X-ray minimum was intermediate between the extended minima seen in 1998.0 and 2003.5 by Rossi X-Ray Timing Explorer (RXTE), and the shorter minimum in 2009.0. The hardness ratios derived from the Swift observations showed a relatively smooth increase to a peak value occurring 40.5 days after the start of the X-ray minimum, though these observations cannot reliably measure the X-ray hardness during the deepest part of the X-ray minimum when contamination by the "central constant emission" component is significant. By comparing the timings of the RXTE and Swift observations near the X-ray minima, we derive an updated X-ray period of P_X_=2023.7+/-0.7days, in good agreement with periods derived from observations at other wavelengths, and we compare the X-ray changes with variations in the HeII4686 emission. The middle of the "Deep Minimum" interval, as defined by the Swift column density variations, is in good agreement with the time of periastron passage derived from the HeII{lambda}4686 line variations.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A122
- Title:
- eta Carinae's 2014.6 spectroscopic event
- Short Name:
- J/A+A/578/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Every 5.5-years, {eta} Car's light curve and spectrum change remarkably across all observed wavelength bands. These so-called spectroscopic events are most likely caused by the close approach of a companion. We compare the recent spectroscopic event in mid-2014 to the events in 2003 and 2009 and investigate long-term trends. Eta Car was observed with HST STIS, VLT UVES, and CTIO 1.5m CHIRON for a period of more than two years in 2012-2015. Archival observations with these instruments cover three orbital cycles and the events of 2003.5, 2009.1, and 2014.6. The STIS spectra provide high spatial resolution and include epochs during the 2014 event when observations from most ground-based observatories were not feasible. The strategy for UVES observations allows for a multidimensional analysis, because each location in the reflection nebula is correlated with a different stellar latitude. Important spectroscopic diagnostics during {eta} Car's events show significant changes in 2014 compared to previous events. While the timing of the first HeII {lambda}4686 flash was remarkably similar to previous events, the HeII equivalent widths were slightly larger, and the line flux increased by a factor of ~7 compared to 2003. The second HeII peak occurred at about the same phase as in 2009, but was stronger. The HeI line flux grew by a factor of ~8 in 2009-2014 compared to 1998-2003. The NII emission lines also increased in strength. On the other hand, H{alpha} and FeII lines show the smallest emission strengths ever observed in {eta} Car. The optical continuum brightened by a factor of ~4 in the past 10-15 years. The polar spectrum shows fewer changes in the broad wind emission lines: the FeII emission strength decreased by a factor of ~2 (compared to a factor of ~4 in our direct line of sight). The HeII equivalent widths at FOS4 were larger in 2009 and 2014 than during the 2003 event.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A106
- Title:
- eta Car velocity-resolved imaging
- Short Name:
- J/A+A/594/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass loss from massive stars is not understood well. eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. We want to investigate the structure and kinematics of eta Car's primary star wind and wind-wind collision zone with a high spatial resolution of ~6mas (~14au) and high spectral resolution of R=12000. Observations of eta Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision.
- ID:
- ivo://nasa.heasarc/etachamain
- Title:
- Eta Chamaeleontis eROSITA EDR Field X-Ray (0.2-2.3 keV) Source Catalog
- Short Name:
- ETACHAMAIN
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains the "main" (0.2-2.3 keV) catalog of the X-ray sources in the eta Chamaeleontis field scan eROSITA observation (OBSID 300004; see Robrade et al., 2022). The nearby young open cluster eta Chamaeleontis was observed by eROSITA/SRG during its CalPV phase for 150 ks. The eROSITA data were taken in the field-scan mode, an observing mode of Spectrum-Roentgen-Gamma (SRG) that follows a rectangular grid-like pattern, covering a 5x5 deg field with an exposure depth of about 5 ks. The authors studied the known members in X-rays and searched for potential new members of the anticipated dispersed low-mass cluster population. Detected sources were identified by cross-matching X-ray sources with Gaia and 2MASS, and young stars were identified by their X-ray activity, by their position in the color-magnitude diagram, and by their astrometric and kinematic properties. X-ray luminosities, light curves, and spectra of cluster members were obtained and compared with previous X-ray data. Literature results of other member searches were used to verify the new member candidates in the observed field. The authors determined X-ray properties of virtually all known eta Cha members and identified five additional stellar systems that showed basically identical characteristics, but are more dispersed. Four of them were previously proposed as potential members; this status is supported by this X-ray study. Based on their spatial distribution, further members are expected beyond the sky region surveyed. The identified stellar systems very likely belong to the ejected halo population, which brings the total number of eta Cha cluster members to at least 23. <a href="/W3Browse/erosita/etachahard.html">ETACHAHARD</a> is the related catalog of hard band (2.3-5.0 keV) sources. This database table was ingested by the HEASARC in August 2022 and is based upon a file downloaded from the eROSITA-DE Early Data Release <a href="https://erosita.mpe.mpg.de/edr/eROSITAObservations/Catalogues/">catalogs web page</a>. In some cases, the HEASARC has altered the original field names, as per HEASARC conventions, and provides the original field names in square brackets. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/etachahard
- Title:
- Eta Chamaeleontis eROSITA EDR Field X-Ray (2.3-5.0 keV) Source Catalog
- Short Name:
- ETACHAHARD
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains the catalog of the X-ray sources in the eta Chamaeleontis field scan eROSITA observation (OBSID 300004; see Robrade et al., 2022) in the hard (2.3-5.0 keV) band. The nearby young open cluster eta Chamaeleontis was observed by eROSITA/SRG during its CalPV phase for 150 ks. The eROSITA data were taken in the field-scan mode, an observing mode of Spectrum-Roentgen-Gamma (SRG) that follows a rectangular grid-like pattern, covering a 5x5 deg field with an exposure depth of about 5 ks. The authors studied the known members in X-rays and searched for potential new members of the anticipated dispersed low-mass cluster population. Detected sources were identified by cross-matching X-ray sources with Gaia and 2MASS, and young stars were identified by their X-ray activity, by their position in the color-magnitude diagram, and by their astrometric and kinematic properties. X-ray luminosities, light curves, and spectra of cluster members were obtained and compared with previous X-ray data. Literature results of other member searches were used to verify the new member candidates in the observed field. The authors determined X-ray properties of virtually all known eta Cha members and identified five additional stellar systems that showed basically identical characteristics, but are more dispersed. Four of them were previously proposed as potential members; this status is supported by this X-ray study. Based on their spatial distribution, further members are expected beyond the sky region surveyed. The identified stellar systems very likely belong to the ejected halo population, which brings the total number of eta Cha cluster members to at least 23. <a href="/W3Browse/erosita/etachamain.html">ETACHAMAIN</a> is the related catalog of main (0.2-2.3 keV) sources. This database table was ingested by the HEASARC in August 2022 and is based upon a file downloaded from the eROSITA-DE Early Data Release <a href="https://erosita.mpe.mpg.de/edr/eROSITAObservations/Catalogues/">catalogs web page</a>. In some cases, the HEASARC has altered the original field names, as per HEASARC conventions, and provides the original field names in square brackets. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/ApJ/810/138
- Title:
- ETGs sample for the Coma cluster
- Short Name:
- J/ApJ/810/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the properties of early-type galaxies (ETGs), including ellipticals (E) and lenticulars (S0), in rich environments, such as clusters of galaxies (Virgo and Coma). The L_24_/L_K_ distribution of ETGs in both Virgo and Coma clusters shows that some S0s have a much larger L_24_/L_K_ ratio (0.5 to ~2 dex) than the bulk of the ETG population. This could be interpreted as an enhanced star formation rate in these lenticulars. We compare the optical colors of galaxies in these two clusters and investigate the nature of these sources with a large L_24_/L_K_ ratio by looking at their spatial distribution within the cluster, analyzing their optical spectra, and looking at their optical colors compared to late-types. We obtain 10 Coma and 3 Virgo early-type sources with larger L_24_/L_K_ ratios than the bulk of their population. We call these sources mid-infrared enhanced galaxies (MIEGs). In Coma, they are mostly located in the southwest part of the cluster where a substructure is falling onto the main cluster. MIEGs present a lower g-r color than the rest of the ETG sample because of a blue continuum. We interpret the excess L_24_/L_K_ ratio as evidence for enhanced star formation induced as a consequence of their infall into the main cluster.