- ID:
- ivo://CDS.VizieR/J/ApJ/823/157
- Title:
- LOS velocities & [Fe/H] of Pal 5 tidal stream
- Short Name:
- J/ApJ/823/157
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Subaru/Faint Object Camera and Spectrograph and Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectroscopy of a tidally disrupting Milky Way (MW) globular cluster Palomar 5 (Pal 5) and its tidal stream. The observed fields are located to cover an angular extent of ~17{deg} along the stream, providing an opportunity to investigate a trend in line-of-sight velocities (V_los_) along the stream, which is essential to constrain its orbit and underlying gravitational potential of the MW's dark matter halo. A spectral fitting technique is applied to the observed spectra to obtain stellar parameters and metallicities ([Fe/H]) of the target stars. The 19 stars most likely belonging to the central Pal 5 cluster have a mean V_los_ of -58.1+/-0.7km/s and metallicity [Fe/H]=-1.35+/-0.06dex, both of which are in good agreement with those derived in previous high-resolution spectroscopic studies. Assuming that the stream stars have the same [Fe/H] as the progenitor cluster, the derived [Fe/H] and V_los_ values are used to estimate the possible V_los_ range of the member stars at each location along the stream. Because of the heavy contamination of the field MW stars, the estimated V_los_ range depends on prior assumptions about the stream's V_los_, which highlights the importance of more definitely identifying the member stars using proper motion and chemical abundances to obtain unbiased information of V_los_ in the outer part of the Pal 5 stream. The models for the gravitational potential of the MW's dark matter halo that are compatible with the estimated V_los_ range are discussed.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/547/A96
- Title:
- Low-mass He-core white dwarfs seismic properties
- Short Name:
- J/A+A/547/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed tabulations of stellar models and pulsational properties for low-mass He-core white dwarf stars, for different stellar masses and effective temperatures. Pulsation periods were computed for g- and p-modes with harmonic degree l=1. The stellar mass ranges from 0.17M_{sun} to 0.45M_{sun}, while the effective temperature ranges from 13000 to 8000K. The pulsation periods are listed in files named ava_m.mmm_g.tgz and ava_m.mmm_p.tgz, for g- and p-modes, respectively, were m.mmm denotes the stellar mass in solar mass units. These files contain a sequence of tables (avannn_m.mmm_g.out and avannn_m.mmm_p.out) corresponding to models with decreasing effective temperature, where nnn correspond to the number of file, starting with nnn=001. In each avannn_m.mmm_g.out and avannn_m.mmm_p.out files, the following quantities are listed: harmonic degree (l), radial order (k), Period, period spacing (DP), kinetic energy (log(Ek)) and first order rotation splitting coefficient (C_kl). The stellar parameters characterizing each model are listed at the top of the table as a header: stellar mass in solar units (M_*/M_{sun}), luminosity in solar units (L_*/L_{sun}), effective temperature in Kelvin (Teff[K]), hydrogen mass in units of the stellar mass (log(M_H/M_*)), age in millions of years (Time [10^6^yr]), and asymptotic period spacing in seconds (DPa [s], for g-modes only). The chemical profiles and critical frequencies are listed in the files par_m.mmm.tgz, which contain a sequence of tables corresponding to models with decreasing effective temperature (parnnn_m.mmm.out). Stellar parameters of each model are listed as a header: stellar mass in solar units (M_*/M_{sun}), effective temperature in Kelvin (Teff[K]), luminosity in solar units (L_*/L_{sun}) and hydrogen mass in units of stellar mass (log(M_H/M_*)). Below the header, the following quantities are listed: normalized radial coordinate (r/R_*), the outer mass fraction coordinate (-log q, with q=1-M_r/M_*), the squared Brunt-Vaisala (N^2^) and Lamb (L^2^) frequencies, the Ledoux term (B Ledoux), and the abundances by mass of hydrogen (H1), helium (He4), carbon (C12) and oxygen (O16).
- ID:
- ivo://CDS.VizieR/J/A+AS/141/371
- Title:
- Low-mass stars evolutionary tracks & isochrones
- Short Name:
- J/A+AS/141/371
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These files contain a large database of stellar models that are suitable to modelling star clusters and galaxies by means of population synthesis. They are based on a large grid of stellar evolutionary tracks for the initial chemical compositions [Z=0.0004, Y=0.23], [Z=0.001, Y=0.23], [Z=0.004, Y=0.24], [Z=0.008, Y=0.25], [Z=0.019, Y=0.273] (solar composition), and [Z=0.03, Y=0.30]. Tracks are computed with updated opacities and equation of state, and a moderate amount of convective overshoot. The range of initial masses goes from 0.15M_{sun}_ to 7M_{sun}_, and the evolutionary phases extend from the zero age main sequence (ZAMS) till either the thermally pulsing AGB regime or carbon ignition. We also present an additional set of models with solar composition, computed using the classical Schwarzschild's criterion for convective boundaries. From all these models, we derive: (1) Tables with the main quantities that characterize the stellar structure along the evolutionary tracks; (2) tables of surface chemical composition after the first and second dredge-up events; (3) extended theoretical isochrones in the Johnson-Cousins UBVRIJHK broad-band photometric system, together with summary tables; (4) integrated colours of single-burst stellar populations.
- ID:
- ivo://CDS.VizieR/J/A+A/462/535
- Title:
- Low-metallicity HII regions and galaxies
- Short Name:
- J/A+A/462/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aims are to estimate the validity of empirical methods, such as R23, R23-P, log([NII]/H{alpha}) (N2), log[([OIII]/H{beta})/([NII]/H{alpha}] (O3N2), and log([SII]/H{alpha}) (S2), and to re-derive (or add) the calibrations of R23, N2, O3N2, and S2 indices for oxygen abundances on the basis of a large sample of galaxies with Te-based abundances. We determined the gas-phase oxygen abundance for a sample of 695 galaxies and HII regions with reliable detections of [OIII]4363, using the reliable and direct temperature-sensitive (Te) method of measuring metallicity. We selected 531 star-forming galaxies from the SDSS-DR4 database with strong emission lines, including [OIII]4363 detected at a signal-to-noise ratio higher than 5{sigma}, as well as 164 galaxies and HII regions from the literature with Te measurements. The O/H abundances were derived from a two-zone model for the temperature structure, assuming a relationship between high ionization and low ionization species.
- ID:
- ivo://CDS.VizieR/J/A+A/494/403
- Title:
- Low temperature Rosseland opacities
- Short Name:
- J/A+A/494/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide low temperature opacity data that incorporate varied abundances of the elements carbon and nitrogen. In the temperature range that we focus at, molecules are the dominant opacity source. Our dataset spans a large metallicity range and shall deliver the necessary input data for stellar evolution models as well as other applications. We conduct chemical equilibrium calculations in order to evaluate the partial pressures of neutral atoms, ions and molecules. Based on a large dataset containing atomic line and continuum data, and, most importantly, a plethora of molecular lines, we subsequently calculate Rosseland mean opacity coefficients. This is done not only for a number of different metallicities, but also for varied abundances of the isotopes ^12^C and ^14^N at each metallicity. The molecular data comprise the main opacity sources at either an oxygen-rich or carbon-rich chemistry. We tabulate the opacity coefficients as a function of temperature and, basically, density. Already within a certain chemistry regime an alteration in the carbon abundance causes, due to the special role of the CO molecule, considerable changes in the Rosseland opacity. The transition from a scaled solar (i.e. oxygen-rich) mixture to the carbon-rich regime results in opacities that can, at low temperatures, be orders of magnitude different compared to the initial situation. The reason is that different molecular absorbers make up the mean opacity in either case. A varying abundance of nitrogen has less pronounced effects but, nevertheless, cannot be neglected.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A57
- Title:
- LQ Hya activity and Li variations
- Short Name:
- J/A+A/575/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the rotational modulation of chromospheric and photospheric parameters of the young, active, single K2 dwarf LQ Hya and their connection with the variability of the LiI 670.8nm line. A total of 199 high-resolution STELLA spectra were used to compute effective temperature, gravity, and chromospheric activity indicators like H{alpha} and H{beta} emission, Balmer decrement, and chromospheric electron density, as a function of the rotational phase. The variation of the LiI 670.8nm line were characterized in terms of equivalent width, abundance, and of ^6^Li/^7^Li isotopic ratio in the form of line shifts.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/899
- Title:
- LVL SEDs and physical properties
- Short Name:
- J/MNRAS/445/899
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the panchromatic spectral energy distributions (SEDs) of the Local Volume Legacy (LVL) survey which consists of 258 nearby galaxies (D<11Mpc). The wavelength coverage spans the ultraviolet to the infrared (1500{AA}-24{mu}m) which is utilized to derive global physical properties (i.e. star formation rate, stellar mass, internal extinction due to dust). With these data, we find colour-colour relationships and correlated trends between observed and physical properties (i.e. optical magnitudes and dust properties, optical colour and specific star formation rate, and ultraviolet-infrared colour and metallicity). The SEDs are binned by different galaxy properties to reveal how each property affects the observed shape of these SEDs. In addition, due to the volume-limited nature of LVL, we utilize the dwarf-dominated galaxy sample to test star formation relationships established with higher mass galaxy samples. We find good agreement with the star-forming `main-sequence' relationship, but find a systematic deviation in the infrared `main sequence' at low luminosities. This deviation is attributed to suppressed polycyclic aromatic hydrocarbon (PAH) formation in low-metallicity environments and/or the destruction of PAHs in more intense radiation fields occurring near a suggested threshold in star formation rates (sSFR) at a value of log(sSFR)~-10.2.
- ID:
- ivo://CDS.VizieR/J/ApJ/811/30
- Title:
- Machine learning metallicity predictions using SDSS
- Short Name:
- J/ApJ/811/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extremely metal-poor (EMP) stars ([Fe/H]<=-3.0dex) provide a unique window into understanding the first generation of stars and early chemical enrichment of the universe. EMP stars are exceptionally rare, however, and the relatively small number of confirmed discoveries limits our ability to exploit these near-field probes of the first ~500Myr after the Big Bang. Here, a new method to photometrically estimate [Fe/H] from only broadband photometric colors is presented. I show that the method, which utilizes machine-learning algorithms and a training set of ~170000 stars with spectroscopically measured [Fe/H], produces a typical scatter of ~0.29dex. This performance is similar to what is achievable via low-resolution spectroscopy, and outperforms other photometric techniques, while also being more general. I further show that a slight alteration to the model, wherein synthetic EMP stars are added to the training set, yields the robust identification of EMP candidates. In particular, this synthetic-oversampling method recovers ~20% of the EMP stars in the training set, at a precision of ~0.05. Furthermore, ~65% of the false positives from the model are very metal-poor stars ([Fe/H]<=-2.0dex). The synthetic-oversampling method is biased toward the discovery of warm (~F-type) stars, a consequence of the targeting bias from the Sloan Digital Sky Survey/Sloan Extension for Galactic Understanding survey. This EMP selection method represents a significant improvement over alternative broadband optical selection techniques. The models are applied to >12 million stars, with an expected yield of ~600 new EMP stars, which promises to open new avenues for exploring the early universe.
- ID:
- ivo://CDS.VizieR/J/AJ/160/103
- Title:
- MACS J1447.4+0827 multiwavelength study
- Short Name:
- J/AJ/160/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusters of galaxies are outstanding laboratories for understanding the physics of supermassive black hole (SMBH) feedback. Here we present the first Chandra, Karl G. Jansky Very Large Array, and Hubble Space Telescope analysis of MACS J1447.4+0827 (z=0.3755), one of the strongest cool core clusters known, in which extreme feedback from its central SMBH is needed to prevent the hot intracluster gas from cooling. Using this multiwavelength approach, including 70ks of Chandra X-ray observations, we detect the presence of collimated jetted outflows that coincide with a southern and a northern X-ray cavity. The total mechanical power associated with these outflows (P_cav_~6x1044erg/s) is roughly consistent with the energy required to prevent catastrophic cooling of the hot intracluster gas (L_cool_=1.71{+/-}0.01x1045erg/s for t_cool_=7.7Gyr), implying that powerful SMBH feedback was in place several Gyr ago in MACS J1447.7+0827. In addition, we detect the presence of a radio minihalo that extends over 300kpc in diameter (P1.4GHz=3.0{+/-}0.3x1024W/Hz). The X-ray observations also reveal an ~20kpc plumelike structure that coincides with optical dusty filaments that surround the central galaxy. Overall, this study demonstrates that the various physical phenomena occurring in the most nearby clusters of galaxies are also occurring in their more distant analogs.
- ID:
- ivo://CDS.VizieR/J/AJ/162/229
- Title:
- 13 Magellanic Clouds metal-poor stars
- Short Name:
- J/AJ/162/229
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- The chemical abundances of a galaxy's metal-poor stellar population can be used to investigate the earliest stages of its formation and chemical evolution. The Magellanic Clouds are the most massive of the Milky Way's satellite galaxies and are thought to have evolved in isolation until their recent accretion by the Milky Way. Unlike the Milky Way's less massive satellites, little is known about the Magellanic Clouds' metal-poor stars. We have used the mid-infrared metal-poor star selection of Schlaufman & Casey and archival data to target nine LMC and four SMC giants for high-resolution Magellan/MIKE spectroscopy. These nine LMC giants with -2.4<~[Fe/H]<~-1.5 and four SMC giants with -2.6<~[Fe/H]<~-2.0 are the most metal-poor stars in the Magellanic Clouds yet subject to a comprehensive abundance analysis. While we find that at constant metallicity these stars are similar to Milky Way stars in their {alpha}, light, and iron-peak elemental abundances, both the LMC and SMC are enhanced relative to the Milky Way in the r-process element europium. These abundance offsets are highly significant, equivalent to 3.9{sigma} for the LMC, 2.7{sigma} for the SMC, and 5.0{sigma} for the complete Magellanic Cloud sample. We propose that the r-process enhancement of the Magellanic Clouds' metal-poor stellar population is a result of the Magellanic Clouds' isolated chemical evolution and long history of accretion from the cosmic web combined with r-process nucleosynthesis on a timescale longer than the core-collapse supernova timescale but shorter than or comparable to the thermonuclear (i.e., Type Ia) supernova timescale.