MaNGA provides the opportunity to make precise spatially resolved measurements of the IMF slope in galaxies owing to its unique combination of spatial resolution, wavelength coverage and sample size. ...We derive radial gradients in age, element abundances and IMF slope analysing optical and near-infrared absorption features from stacked spectra out to the half-light radius of 366 early-type galaxies with masses \(9.9 - 10.8\;\log M/M_{\odot}\). We find flat gradients in age and \(\alpha\)/Fe ratio, as well as negative gradients in metallicity, consistent with the literature. We further derive significant negative gradients in the Na/Fe ratio with galaxy centres being well enhanced in Na abundance by up to 0.5 dex. Finally, we find a gradient in IMF slope with a bottom-heavy IMF in the centre (typical mass excess factor of 1.5) and a Milky Way-type IMF at the half-light radius. This pattern is mass-dependent with the lowest mass galaxies in our sample featuring only a shallow gradient around a Milky Way IMF. Our results imply the local IMF-\(\sigma\) relation within galaxies to be even steeper than the global relation and hint towards the local metallicity being the dominating factor behind the IMF variations. We also employ different stellar population models in our analysis and show that a radial IMF gradient is found independently of the stellar population model used. A similar analysis of the Wing-Ford band provides inconsistent results and further evidence of the difficulty in measuring and modelling this particular feature.
We present the first scientific results from the luminous red galaxy sample (LRG) of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We measure the small and intermediate scale ...clustering from a sample of more than 61,000 galaxies in the redshift range \(0.6 < z < 0.9\). We interpret these measurements in the framework of the Halo Occupation Distribution. The bias of eBOSS LRGs is \(2.30 \pm 0.03\), with a satellite fraction of \(13\pm3\)\% and a mean halo mass of \(2.5\times10^{13}h^{-1}M_{\odot}\). These results are consistent with expectations, demonstrating that eBOSS galaxies will be reliable tracers of large scale structure at \(z\sim 0.7\). The eBOSS galaxy bias implies a scatter of luminosity at fixed halo mass, \(\sigma_{\log L}\), of 0.19 dex. Using the clustering of massive galaxies from BOSS-CMASS, BOSS-LOWZ, and SDSS, we find that \(\sigma_{\log L}=0.19\) is consistent with observations over the full redshift range that these samples cover. The addition of eBOSS to previous surveys allows investigation of the evolution of massive galaxies over the past \(\sim 7\) Gyr.
We utilize elemental-abundance information for Galactic red giant stars in five open clusters (NGC 7789, NGC 6819, M67, NGC 188, and NGC 6791) from the Apache Point Observatory Galactic Evolution ...Experiment (APOGEE) DR13 dataset to age-date the chemical evolution of the high- and low-\(\alpha\) element sequences of the Milky Way. Key to this time-stamping is the cluster NGC 6791, whose stellar members have mean abundances that place it in the high-\(\alpha\), high-Fe/H region of the \(\alpha\)/Fe-Fe/H plane. Based on the cluster's age (\(\sim 8\) Gyr), Galactocentric radius, and height above the Galactic plane, as well as comparable chemistry reported for APOGEE stars in Baade's Window, we suggest that the two most likely origins for NGC 6791 are as an original part of the thick-disk, or as a former member of the Galactic bulge. Moreover, because NGC 6791 lies at the \textit{high metallicity end} (Fe/H \(\sim 0.4\)) of the high-\(\alpha\) sequence, the age of NGC 6791 places a limit on the \textit{youngest age} of stars in the high-metallicity, high-\(\alpha\) sequence for the cluster's parent population (i.e., either the bulge or the disk). In a similar way, we can also use the age and chemistry of NGC 188 to set a limit of \(\sim 7\) Gyr on the \textit{oldest age} of the low-\(\alpha\) sequence of the Milky Way. Therefore, NGC 6791 and NGC 188 are potentially a pair of star clusters that bracket both the timing and the duration of an important transition point in the chemical history of the Milky Way.
We present a semi-empirical spectral classification scheme for normal B-type stars using near-infrared spectra (1.5-1.7 \(\mu\)m) from the SDSS APOGEE2-N DR14 database. The main motivation for ...working with B-type stars is their importance in the evolution of young stellar clusters, however we also take advantage of having a numerous sample (316 stars) of B-type star candidates in APOGEE2-N, for which we also have optical (3600-9100 \angstrom) counterparts from the LAMOST survey. By first obtaining an accurate spectral classification of the sources using the LAMOST DR3 spectra and the canonical spectral classification scheme Gray & Corbally 2009, we found a linear relation between optical spectral types and the equivalent widths of the hydrogen lines of the Brackett series in the APOGEE2-N NIR spectra. This relation extends smoothly from a similar relation for O and early-B stars found by Roman-Lopes et al. (2018). This way, we obtain a catalog of B-type sources with features in both the optical and NIR, and a classification scheme refined down to one spectral sub-class.
We report the discovery of a mysterious giant \(H_{\alpha}\) blob that is \(\sim 8\) kpc away from the main MaNGA target 1-24145, one component of a dry galaxy merger, identified in the first-year ...SDSS-IV MaNGA data. The size of the \(H_{\alpha}\) blob is \(\sim\) 3-4 kpc in radius, and the \(H_{\alpha}\) distribution is centrally concentrated. However, there is no optical continuum counterpart in deep broadband images reaching \(\sim\)26.9 mag arcsec\(^{-2}\) in surface brightness. We estimate that the masses of ionized and cold gases are \(3.3 \times 10^{5}\) \(\rm M_{\odot}\) and \(< 1.3 \times 10^{9}\) \(\rm M_{\odot}\), respectively. The emission-line ratios indicate that the \(H_{\alpha}\) blob is photoionized by a combination of massive young stars and AGN. Furthermore, the ionization line ratio decreases from MaNGA 1-24145 to the \(H_{\alpha}\) blob, suggesting that the primary ionizing source may come from MaNGA 1-24145, likely a low-activity AGN. Possible explanations of this \(H_{\alpha}\) blob include AGN outflow, the gas remnant being tidally or ram-pressure stripped from MaNGA 1-24145, or an extremely low surface brightness (LSB) galaxy. However, the stripping scenario is less favoured according to galaxy merger simulations and the morphology of the \(H_{\alpha}\) blob. With the current data, we can not distinguish whether this \(H_{\alpha}\) blob is ejected gas due to a past AGN outburst, or a special category of `ultra-diffuse galaxy' (UDG) interacting with MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA 1-24145.
Astron.J.126:1896,2003 We report the discovery of a young massive stellar cluster embedded in an
extended HII region, invisible at optical wavelengths where the extinction is
$A_V \approx 28$ ...magnitudes, associated with the IRAS source 16177-5018. $J, H$
and nb$K$ imaging photometry combined with the $K_S$ 2MASS data show the
presence of sources with infrared excess emission at 2.2 $\mu$m, concentrated
in an area of about one square parsec around a massive young stellar object
identified as the IRAS source. This object has a near-mid infrared spectral
index betweem 2.2 and 25 $\mu$m $\alpha({\rm IR}) = d {\rm log}(\lambda
F_\lambda)/d {\rm log} \lambda $ =4.78, characteristic of compact H II regions,
with bolometric luminosity, inferred from the integrated near to far-infrared
flux density of $2.8 \times 10^5 L_\odot$, which corresponds to a ZAMS star of
about $42 M_\odot$. From the color-magnitude diagram we were able to classify
the majority of the cluster members as reddened massive stars earlier than
spectral type B5.
We report the discovery of a young massive stellar cluster embedded in an extended HII region, invisible at optical wavelengths where the extinction is \(A_V \approx 28\) magnitudes, associated with ...the IRAS source 16177-5018. \(J, H\) and nb\(K\) imaging photometry combined with the \(K_S\) 2MASS data show the presence of sources with infrared excess emission at 2.2 \(\mu\)m, concentrated in an area of about one square parsec around a massive young stellar object identified as the IRAS source. This object has a near-mid infrared spectral index betweem 2.2 and 25 \(\mu\)m \(\alpha({\rm IR}) = d {\rm log}(\lambda F_\lambda)/d {\rm log} \lambda \) =4.78, characteristic of compact H II regions, with bolometric luminosity, inferred from the integrated near to far-infrared flux density of \(2.8 \times 10^5 L_\odot\), which corresponds to a ZAMS star of about \(42 M_\odot\). From the color-magnitude diagram we were able to classify the majority of the cluster members as reddened massive stars earlier than spectral type B5.
We report the discovery of a young massive stellar cluster and infrared nebula in the direction of the CS molecular cloud associated to the IRAS point source 16132-5039. The analysis of the ...mid-infrared images from the more accurate MSX catalog, reveled that there are two independent components associated with the IRAS source. The integral of the spectral energy distribution for these components, between 8.28 \(\mu\)m and 100 \(\mu\)m, gave lower limits for the bolometric luminosity of the embedded objects of \(8.7 \times 10^4 L_\odot\) and \(9 \times 10^3 L_\odot\), which corresponds to ZAMS O8 and B0.5 stars, respectively. The number of Lyman continuum photons expected from the stars that lie along the reddening line for early-type stars is about 1.7 \( \times\) 10\(^{49}\) s\(^{-1}\), enough to produce the detected flux densities at 5 GHz. The NIR spectrum of the nebula increases with frequency, implying that free-free emission cannot be the main source of the extended luminosity, from which we conclude that the observed emission must be mainly dust scattered light. A comparison of the cluster described in this paper with the young stellar cluster associated with the IRAS source 16177-5018, which is located at the same distance and direction, shows that the mean visual absorption of the newly discovered cluster is about 10 magnitudes smaller and it contains less massive stars, suggesting that it was formed from a less massive molecular cloud.
High-potency benzodiazepines, such as clonazepam, are frequently used in the treatment of panic disorder (PD) because of their rapid onset of action and good tolerability. However, there is concern ...about their potential to cause withdrawal symptoms. We aimed to develop a protocol for safely tapering off clonazepam in patients with PD who had been receiving treatment for at least 3 years. A specific scale for judging withdrawal was also developed, the Composite Benzodiazepine Discontinuation Symptom Scale. We selected 73 patients with PD who had been asymptomatic for at least 1 year and who wished to discontinue the medication. The trial consisted of a 4-month period of tapering and an 8-month follow-up period. The dosage of clonazepam was decreased by 0.5 mg per 2-week period until 1 mg per day was reached, followed by a decrease of 0.25 mg per week. The mean dosage at the start of tapering was 2.7 +/- 1.2 mg/d. In total, 51 (68.9%) of the patients were free of the medication after the 4 months of tapering according to the protocol, and 19 (26.0%) of the patients needed another 3 months to be free of medication. Clonazepam discontinuation symptoms were mostly mild and included mainly: anxiety, shaking/trembling/tremor, nausea/vomiting, insomnia/nightmares, excessive sweating, tachycardia/palpitations, headache, weakness, and muscle aches. The improvement in PD and general well-being was maintained during both the taper and follow-up phases. Clonazepam can be successfully discontinued without any major withdrawal symptoms if the dose is reduced gradually. We recommend reducing the dosage of clonazepam after intermediate-term use by 0.25 mg/wk.
