More Like this

1. The IGRINS YSO Survey. III. Stellar Parameters of Pre-main-sequence Stars in Ophiuchus and Upper Scorpius

   https://doi.org/10.3847/1538-4357/acab04  

   López-Valdivia, Ricardo; Mace, Gregory N.; Han, Eunkyu; Sawczynec, Erica; Hernández, Jesús; Prato, L.; Johns-Krull, Christopher M.; Oh, Heeyoung; Lee, Jae-Joon; Kraus, Adam; et al (January 2023, The Astrophysical Journal)

   Abstract We used the Immersion GRating Infrared Spectrometer (IGRINS) to determine fundamental parameters for 61 K- and M-type young stellar objects (YSOs) located in the Ophiuchus and Upper Scorpius star-forming regions. We employed synthetic spectra and a Markov chain Monte Carlo approach to fit specificK-band spectral regions and determine the photospheric temperature (T), surface gravity ( $\log g$), magnetic field strength (B), projected rotational velocity ( $v\sin i$), andK-band veiling (r_K). We determinedBfor ∼46% of our sample. Stellar parameters were compared to the results from Taurus-Auriga and the TW Hydrae association presented in Paper I of this series. We classified all the YSOs in the IGRINS survey with infrared spectral indices from Two Micron All Sky Survey and Wide-field Infrared Survey Explorer photometry between 2 and 24μm. We found that Class II YSOs typically have lower $\log g$and $v\sin i$, similarB, and higherK-band veiling than their Class III counterparts. Additionally, we determined the stellar parameters for a sample of K and M field stars also observed with IGRINS. We have identified intrinsic similarities and differences at different evolutionary stages with our homogeneous determination of stellar parameters in the IGRINS YSO survey. Considering $\log g$as a proxy for age, we found that the Ophiuchus and Taurus samples have a similar age. We also find that Upper Scorpius and TWA YSOs have similar ages, and are more evolved than Ophiuchus/Taurus YSOs. 

   more » « less
2. Is [Y/Mg] a Reliable Age Diagnostic for FGK Stars?

   https://doi.org/10.3847/1538-4357/ac8746  

   Berger, Travis A.; van Saders, Jennifer L.; Huber, Daniel; Gaidos, Eric; Schlieder, Joshua E.; Claytor, Zachary R. (September 2022, The Astrophysical Journal)

   Abstract Current spectroscopic surveys are producing large catalogs of chemical abundances for stars of all types. The yttrium-to-magnesium ratio, [Y/Mg], has emerged as a candidate age indicator for solar twins in the local stellar neighborhood. However, it is unclear whether it is a viable age diagnostic for more diverse stellar types, so we investigate [Y/Mg] as an age indicator for the FGK-type planet host stars observed by Kepler. We find that the [Y/Mg] “Clock” is most precise for solar twins, with a [Y/Mg]/age slope ofm= −0.0370 ±0.0071 dex Gyr⁻¹andσ_Age= 2.6 Gyr. We attribute the lower precision compared to literature results to nonsolar twins contaminating our solar twin sample and recommend a 1.5 Gyr systematic uncertainty for stellar ages derived with any [Y/Mg]–Age relation. We also analyzed the [Y/Mg] Clock as a function ofT_eff, $\log g$, and metallicity individually and find no strong trends, but we compute statistically significant [Y/Mg]–Age relations for subsamples defined by ranges inT_eff, $\log g$, and metallicity. Finally, we compare [Y/Mg] and rotation ages and find statistically similar trends as for isochrone ages, although we find that rotation ages perform better for GK dwarfs while isochrones perform better for FG subgiants. We conclude that the [Y/Mg] Clock is most precise for solar twins and analogs but is also a useful age diagnostic for FGK stars. 

   more » « less
3. Pressure-induced shift of effective Ce valence, Fermi energy and phase boundaries in CeOs ₄ Sb ₁₂

   https://doi.org/10.1088/1367-2630/ac643c  

   Götze, K.; Pearce, M. J.; Coak, M. J.; Goddard, P. A.; Grockowiak, A. D.; Coniglio, W. A.; Tozer, S. W.; Graf, D. E.; Maple, M. B.; Ho, P-C; et al (April 2022, New Journal of Physics)

   Abstract CeOs₄Sb₁₂, a member of the skutterudite family, has an unusual semimetallic low-temperature $\mathcal{L}$-phase that inhabits a wedge-like area of the fieldH—temperatureTphase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs₄Sb₁₂single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the differentH–Tphase boundaries. While the high-temperature valence transition between the metallic $\mathcal{H}$-phase and the $\mathcal{L}$-phase is shifted to higherTby pressures of the order of 1 GPa, we observed only a marginal suppression of the $\mathcal{S}$-phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the $\mathcal{H}$-phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs₄Sb₁₂which appears to be limited to the low-field region. 

   more » « less
4. Constraining Cosmological Parameters Using the Cluster Mass–Richness Relation

   https://doi.org/10.3847/1538-4357/ace773  

   Abdullah, Mohamed H.; Wilson, Gillian; Klypin, Anatoly; Ishiyama, Tomoaki (September 2023, The Astrophysical Journal)

   Abstract The cluster mass–richness relation (MRR) is an observationally efficient and potentially powerful cosmological tool for constraining the matter density Ω_mand the amplitude of fluctuationsσ₈using the cluster abundance technique. We derive the MRR relation usingGalWCat19, a publicly available galaxy cluster catalog we created from the Sloan Digital Sky Survey-DR13 spectroscopic data set. In the MRR, cluster mass scales with richness as $\log M_{200}=\alpha +\beta \log N_{200}$. We find that the MRR we derive is consistent with both the IllustrisTNG and mini-Uchuu cosmological numerical simulations, with a slope ofβ≈ 1. We use the MRR we derived to estimate cluster masses from theGalWCat19catalog, which we then use to set constraints on Ω_mandσ₈. Utilizing the all-member MRR, we obtain constraints of Ω_m= ${0.31}_{-0.03}^{+0.04}$andσ₈= ${0.82}_{-0.04}^{+0.05}$, and utilizing the red member MRR only, we obtain Ω_m= ${0.31}_{-0.03}^{+0.04}$andσ₈= ${0.81}_{-0.04}^{+0.05}$. Our constraints on Ω_mandσ₈are consistent and very competitive with the Planck 2018 results. 

   more » « less
5. The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). III. The Mass Function of Young Stellar Clusters in M33

   https://doi.org/10.3847/1538-4357/ac51cf  

   Wainer, Tobin M.; Johnson, L. Clifton; Seth, Anil C.; TorresVillanueva, Estephani E.; Dalcanton, Julianne J.; Durbin, Meredith J.; Dolphin, Andrew; Weisz, Daniel R.; Williams, Benjamin F.; PHATTER Collaboration (March 2022, The Astrophysical Journal)

   Abstract We measure the star cluster mass function (CMF) for the Local Group galaxy M33. We use the catalog of stellar clusters selected from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey. We analyze 711 clusters in M33 with $7.0<\log \left(\mathrm{Age}/\mathrm{yr}\right)<8.5$, and log(M/M_⊙) > 3.0 as determined from color–magnitude diagram fits to individual stars. The M33 CMF is best described by a Schechter function with power-law slopeα= − ${2.06}_{-0.13}^{+0.14}$, and truncation mass log(M_c/M_⊙) $={4.24}_{-0.13}^{+0.16}$. The data show strong evidence for a high-mass truncation, thus strongly favoring a Schechter function fit over a pure power law. M33's truncation mass is consistent with the previously identified linear trend betweenM_c, and star formation rate surface density, Σ_SFR. We also explore the effect that individual cluster mass uncertainties have on derived mass function parameters, and find evidence to suggest that large cluster mass uncertainties have the potential to bias the truncation mass of fitted mass functions at the 1σlevel. 

   more » « less