Assessing molecular outflows and turbulence in the protostellar cluster Serpens South

Molecular outflows driven by protostellar cluster members likely impact their surroundings and contribute to turbulence, affecting subsequent star formation. The very young Serpens South cluster consists of a particularly high density and fraction of protostars, yielding a relevant case study for protostellar outflows and their impact on the cluster environment. We combined CO $J=1-0$ observations of this region using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie Millim\'{e}trique (IRAM) 30 m single dish telescope. The combined map allows us to probe CO outflows within the central, most active region at size scales of 0.01 pc to 0.8 pc. We account for effects of line opacity and excitation temperature variations by incorporating $^{12}$CO and $^{13}$CO data for the $J=1-0$ and $J=3-2$ transitions (using Atacama Pathfinder Experiment and Caltech Submillimeter Observatory observations for the higher CO transitions), and we calculate mass, momentum, and energy of the molecular outflows in this region. The outflow mass loss rate, force, and luminosity, compared with diagnostics of turbulence and gravity, suggest that outflows drive a sufficient amount of energy to sustain turbulence, but not enough energy to substantially counter the gravitational potential energy and disrupt the clump. Further, we compare Serpens South with the slightly more evolved cluster NGC 1333, and we propose an empirical scenario for outflow-cluster interaction at different evolutionary stages.Comment: 26 pages, 15 figures, accepted for publication in the Astrophysical Journa

The evolution of Araliaceae : a phylogenetic analysis based on ITS sequences of nuclear ribosomal DNA

Phylogenetic analyses of ITS sequence data from 70 species and 40 genera of Araliaceae (representing all major lineages within the "core group" of the family) do not support the widely used traditional division of Araliaceae into three tribes. Tribe Aralieae (characterized by imbricate petals) is found nested within a paraphyletic Schefflerieae (whose taxa have valvate petals). There are, however, two large monophyletic groups comprising most araliad genera: the "Aralia-Polyscias-Pseudopanax group" (which includes Aralia, Meryta, Munroidendron, Panax, Pentapanax, Polyscias, Pseudopanax, Reynoldsia, Sciadodendron, Tetraplasandra, and their close allies), and the "Eleutherococcus-Dendropanax-Schefflera group" (including Brassaiopsis, Dendropanax, Eleutherococcus, Fatsia, Hedera, Oreopanax, Schefflera, Sinopanax, and their close allies). The ITS trees also permit a re-evaluation of several taxonomically important morphological characters (e.g., petal aestivation, leaf architecture, carpel number, and habit), and provide the opportunity to assess traditional generic delimitations in the family. Four of the largest genera appear to be either polyphyletic (Schefflera, Pseudopanax) or paraphyletic (Aralia, Polyscias), but further studies will be needed to fully re-define these complex taxa. Outgroup comparisons and the placement of Astrotricha and Osmoxylon (in basally-branching lineages in Araliaceae) help to confirm a paleotropical origin of the family. The ITS topologies suggest that biogeographic radiations into different tropical/subtropical regions and into the north and south temperate regions occurred early in the history of core Araliaceae. Temperate taxa have arisen several times independently from tropical and subtropical relatives, although a few subtropical taxa may be found nested within temperate clades (e.g., Pentapanax within Aralia). Migrations between the Old and New Worlds are also suggested for several taxa, including Aralia, Panax, Oplopanax, and the Sinopanax-Oreopanax generic pair

CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud

We present the N2H+(J=1-0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 250 square arcminutes and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km/s, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N2H+ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N2H+ filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence.Comment: 12 pages, 4 figures, published in ApJL (July 2014

Relationship between solar energetic oxygen flux and MHD shock Mach number

This study correlates the time-intensity profile of a magnetohydrodynamic (MHD) shock with the corresponding solar energetic oxygen for a coronal mass ejection (CME) event that occurred on October 28, 2003. The intensity of MHD shock, in terms of Mach number, is simulated using a 1.5D MHD code, whereas the solar energetic oxygen flux is observed by the Solar Isotope Spectrometer (SIS) on board the Advanced Composition Explorer (ACE) spacecraft. A good correlation (Pearson correlation coefficient: r = 0.70 – 0.84) is found between the forward fast-mode shock Mach number and the hourly-averaged, logarithmic oxygen differential energy flux for 7 energy channels (7.3 – 63.8 MeV). We suspect that the intensity-time profile of high energy SEP events is manifested by the strength (Mach number) of CME-driven propagation shocks. While further studies with more events are required to be more conclusive, this study result provides a direction for future studies or predictions of SEP fluxes

CARMA Large Area Star Formation Survey: Project Overview with Analysis of Dense Gas Structure and Kinematics in Barnard 1

We present details of the CARMA Large Area Star Formation Survey (CLASSy), while focusing on observations of Barnard 1. CLASSy is a CARMA Key Project that spectrally imaged N2H+, HCO+, and HCN (J=1-0 transitions) across over 800 square arcminutes of the Perseus and Serpens Molecular Clouds. The observations have angular resolution near 7" and spectral resolution near 0.16 km/s. We imaged ~150 square arcminutes of Barnard 1, focusing on the main core, and the B1 Ridge and clumps to its southwest. N2H+ shows the strongest emission, with morphology similar to cool dust in the region, while HCO+ and HCN trace several molecular outflows from a collection of protostars in the main core. We identify a range of kinematic complexity, with N2H+ velocity dispersions ranging from ~0.05-0.50 km/s across the field. Simultaneous continuum mapping at 3 mm reveals six compact object detections, three of which are new detections. A new non-binary dendrogram algorithm is used to analyze dense gas structures in the N2H+ position-position-velocity (PPV) cube. The projected sizes of dendrogram-identified structures range from about 0.01-0.34 pc. Size-linewidth relations using those structures show that non-thermal line-of-sight velocity dispersion varies weakly with projected size, while rms variation in the centroid velocity rises steeply with projected size. Comparing these relations, we propose that all dense gas structures in Barnard 1 have comparable depths into the sky, around 0.1-0.2 pc; this suggests that over-dense, parsec-scale regions within molecular clouds are better described as flattened structures rather than spherical collections of gas. Science-ready PPV cubes for Barnard 1 molecular emission are available for download.Comment: Accepted to The Astrophysical Journal (ApJ), 51 pages, 27 figures (some with reduced resolution in this preprint); Project website is at http://carma.astro.umd.edu/class

Must we measure what we mean?

This paper excavates a debate concerning the claims of ordinary language philosophers that took place during the middle of the last century. The debate centers on the status of statements about “what we say”. On one side of the debate, critics of ordinary language philosophy argued that statements about “what we say” should be evaluated as empirical observations about how people do in fact speak, on a par with claims made in the language sciences. By that standard, ordinary language philosophers were not entitled to the claims that they made about what we would say about various topics. On the other side of the debate, defenders of the methods of ordinary language philosophy sought to explain how philosophers can be entitled to statements about what we would say without engaging in extensive observations of how people do in fact use language. In this paper I defend the idea that entitlement to claims about what we say can be had in a way that doesn’t require empirical observation, and I argue that ordinary language philosophers are (at least sometimes) engaged in a different project than linguists or empirically minded philosophers of language, which is subject to different conditions of success

The Loss of Telomerase Activity in Highly Differentiated CD8+CD28−CD27− T Cells Is Associated with Decreased Akt (Ser473) Phosphorylation

The enzyme telomerase is essential for maintaining the replicative capacity of memory T cells. Although CD28 costimulatory signals can up-regulate telomerase activity, human CD8 + T cells lose CD28 expression after repeated activation. Nevertheless, telomerase is still inducible in CD8 + CD28 − T cells. To identify alternative costimulatory pathways that may be involved, we introduced chimeric receptors containing the signaling domains of CD28, CD27, CD137, CD134, and ICOS in series with the CD3 zeta (ζ) chain into primary human CD8 + T cells. Although CD3 ζ-chain signals alone were ineffective, triggering of all the other constructs induced proliferation and telomerase activity. However, not all CD8 + CD28 − T cells could up-regulate this enzyme. The further fractionation of CD8 + CD28 − T cells into CD8 + CD28 − CD27 + and CD8 + CD28 − CD27 − subsets showed that the latter had significantly shorter telomeres and extremely poor telomerase activity. The restoration of CD28 signaling in CD8 + CD28 − CD27 − T cells could not reverse the low telomerase activity that was not due to decreased expression of human telomerase reverse transcriptase, the enzyme catalytic subunit. Instead, the defect was associated with decreased phosphorylation of the kinase Akt, that phosphorylates human telomerase reverse transcriptase to induce telomerase activity. Furthermore, the defective Akt phosphorylation in these cells was specific for the Ser 473 but not the Thr 308 phosphorylation site of this molecule. Telomerase down-regulation in highly differentiated CD8 + CD28 − CD27 − T cells marks their inexorable progress toward a replicative end stage after activation. This limits the ability of memory CD8 + T cells to be maintained by continuous proliferation in vivo