Star formation in Chamaeleon I and III: a molecular line study of the starless core population

The Chamaeleon clouds are excellent targets for low-mass star formation studies. Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. We aim to determine the driving factors that have led to the very different levels of star formation activity in Cha I and III and examine the dynamical state and possible evolution of the starless cores within them. Observations were performed in various molecular transitions with APEX and Mopra. Five cores are gravitationally bound in Cha I and one in Cha III. The infall signature is seen toward 8-17 cores in Cha I and 2-5 cores in Cha III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the cores in Cha III that are contracting and may become prestellar. Future dynamical interactions between the cores will not be dynamically significant in either Cha I or III, but the subregion Cha I North may experience collisions between cores within ~0.7 Myr. Turbulence dissipation in the cores of both clouds is seen in the high-density tracers N2H+ 1-0 and HC3N 10-9. Evidence of depletion in the Cha I core interiors is seen in the abundance distributions of C17O, C18O, and C34S. Both contraction and static chemical models indicate that the HC3N to N2H+ abundance ratio is a good evolutionary indicator in the prestellar phase for both gravitationally bound and unbound cores. In the framework of these models, we find that the cores in Cha III and the southern part of Cha I are in a similar evolutionary stage and are less chemically evolved than the central region of Cha I. The measured HC3N/N2H+ abundance ratio and the evidence for contraction motions seen towards the Cha III starless cores suggest that Cha III is younger than Cha I Centre and that some of its cores may form stars in the future. The cores in Cha I South may on the other hand be transient structures. (abridged)Comment: Accepted for publication in A&A. The resolution of Figure 2 has been degraded and the abstract in the metadata has been shortened to fit within the limits set by arXi

Imaging Polarimetric Observations of a New Circumstellar Disk System

Few circumstellar disks have been directly observed. Here we use sensitive differential polarimetric techniques to overcome atmospheric speckle noise in order to image the circumstellar material around HD 169142. The detected envelope or disk is considerably smaller than expectations based on the measured strength of the far-IR excess from this system

Student Engagement: A Study of the Relationship between Teacher Credibility and Student Self-Efficacy

Given the current economic and subsequent employment uncertainty, people are returning to college to update their skills and acquire the credentials they need to be competitive in today\u27s workforce. As a result, faculty must be prepared to facilitate the learning process for an ever-changing and more diverse student body. The purpose of this research is to further the extant body of research in the area of effective student engagement. The variables being used to represent credibility are competence, goodwill and trustworthiness. They were measured using McCroskey and Teven\u27s (1999) Source Credibility Questionnaire. The data for this study were provided by students attending a community college located in the metropolitan area of a Midwestern city. Using competence, trustworthiness and goodwill as the antecedents to represent instructor credibility, this research tests the relationship between instructor credibility and student self-efficacy. Conducting a study of this type will provide faculty and administrators looking for new approaches to teacher leadership with data to help them enhance student engagement and increase their rate of persistence to graduation

C-banding And Fish In Chromosomes Of The Blow Flies Chrysomya Megacephala And Chrysomya Putoria (diptera, Calliphoridae).

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.96371-

Deuterated formaldehyde in rho Ophiuchi A

From mapping observations of H2CO, HDCO, and D2CO, we have determined how the degree of deuterium fractionation changes over the central 3'x3' region of rho Oph A. The multi-transition data of the various H2CO isotopologues, as well as from other molecules (e.g., CH3OH and N2D+) present in the observed bands, were analysed using both the standard type rotation diagram analysis and, in selected cases, a more elaborate method of solving the radiative transfer for optically thick emission. In addition to molecular column densities, the analysis also estimates the kinetic temperature and H2 density. Toward the SM1 core in rho Oph A, the H2CO deuterium fractionation is very high. In fact, the observed D2CO/HDCO ratio is 1.34+/-0.19, while the HDCO/H2CO ratio is 0.107+/-0.015. This is the first time, to our knowledge, that the D2CO/HDCO abundance ratio is observed to be greater than 1. The kinetic temperature is in the range 20-30 K in the cores of rho Oph A, and the H2 density is (6-10)x10^5 cm-3. We estimate that the total H2 column density toward the deuterium peak is (1-4)x10^23 cm-2. As depleted gas-phase chemistry is not adequate, we suggest that grain chemistry, possibly due to abstraction and exchange reactions along the reaction chain H2CO -> HDCO -> D2CO, is at work to produce the very high deuterium levels observed.Comment: 17 pages, 11 figures, accepted for publication in Astronomy & Astrophysic

The Influence of Emotional Carrying Capacity and Network Ethnic Diversity on Entrepreneurial Self- Efficacy: The Case of Black and White Entrepreneurs

Purpose: One key determinant of entrepreneurial success is entrepreneurial self-efficacy (ESE), defined as an individual’s confidence in his or her ability to perform entrepreneurial tasks. Whereas previous research has examined how individual and business factors influence ESE, the purpose of this paper is to analyze the influence of entrepreneurs’ social networks upon ESE. The paper examines such relationships for black and white entrepreneurs. Design/methodology/approach: In total, 110 black and white entrepreneurs responded to a survey measuring ESE and critical constructs representing elements of the quality of entrepreneurs’ networks: emotional carrying capacity (ECC) and network ethnic diversity. Findings: The authors found significant, positive relationships between both ECC and network ethnic diversity on ESE for white entrepreneurs but only found a significant positive relationship between ECC and ESE for black entrepreneurs. Originality/value: While research is clear about the role that ESE plays in entrepreneurial activities, few studies have focused on the factors that improve ESE. In the present work, the authors study the role of context by examining how entrepreneurs’ social networks influence ESE. The authors examine such influences for both white and black entrepreneurs to better understand the implications of ethnicity

The evolutionary state of the southern dense core Cha-MMS1

Aims: Our goal is to set constraints on the evolutionary state of the dense core Cha-MMS1 in the Chamaeleon I molecular cloud. Methods: We analyze molecular line observations carried out with the new submillimeter telescope APEX. We look for outflow signatures around the dense core and probe its chemical structure, which we compare to predictions of models of gas-phase chemistry. We also use the public database of the Spitzer Space Telescope (SST) to compare Cha-MMS1 with the two Class 0 protostars IRAM 04191 and L1521F, which are at the same distance. Results: We measure a large deuterium fractionation for N2H+ (11 +/- 3 %), intermediate between the prestellar core L1544 and the very young Class 0 protostar L1521F. It is larger than for HCO+ (2.5 +/- 0.9 %), which is probably the result of depletion removing HCO+ from the high-density inner region. Our CO(3-2) map reveals the presence of a bipolar outflow driven by the Class I protostar Ced 110 IRS 4 but we do not find evidence for an outflow powered by Cha-MMS1. We also report the detection of Cha-MMS1 at 24, 70 and 160 microns by the instrument MIPS of the SST, at a level nearly an order of magnitude lower than IRAM 04191 and L1521F. Conclusions: Cha-MMS1 appears to have already formed a compact object, either the first hydrostatic core at the very end of the prestellar phase, or an extremely young protostar that has not yet powered any outflow, at the very beginning of the Class 0 accretion phase.Comment: Accepted by Astronomy & Astrophysics as a letter, to appear in the special issue on the APEX first result

H2CO and CH3OH maps of the Orion Bar photodissociation region

A previous analysis of methanol and formaldehyde towards the Orion Bar concluded that the two molecular species may trace different physical components, methanol the clumpy material, and formaldehyde the interclump medium. To verify this hypothesis, we performed multi-line mapping observations of the two molecules to study their spatial distributions. The observations were performed with the IRAM-30m telescope at 218 and 241 GHz, with an angular resolution of ~11''. Additional data for H2CO from the Plateau de Bure array are also discussed. The data were analysed using an LVG approach. Both molecules are detected in our single-dish data. Our data show that CH3OH peaks towards the clumps of the Bar, but its intensity decreases below the detection threshold in the interclump material. When averaging over a large region of the interclump medium, the strongest CH3OH line is detected with a peak intensity of ~0.06K. Formaldehyde also peaks on the clumps, but it is also detected in the interclump gas. We verified that the weak intensity of CH3OH in the interclump medium is not caused by the different excitation conditions of the interclump material, but reflects a decrease in the column density of methanol. The abundance of CH3OH relative to H2CO decreases by at least one order of magnitude from the dense clumps to the interclump medium.Comment: 11 pages, accepted for publication in A&

Detection of OD towards the low-mass protostar IRAS16293-2422

Although water is an essential and widespread molecule in star-forming regions, its chemical formation pathways are still not very well constrained. Observing the level of deuterium fractionation of OH, a radical involved in the water chemical network, is a promising way to infer its chemical origin. We aim at understanding the formation mechanisms of water by investigating the origin of its deuterium fractionation. This can be achieved by observing the abundance of OD towards the low-mass protostar IRAS16293-2422, where the HDO distribution is already known. Using the GREAT receiver on board SOFIA, we observed the ground-state OD transition at 1391.5 GHz towards the low-mass protostar IRAS16293-2422. We also present the detection of the HDO 111-000 line using the APEX telescope. We compare the OD/HDO abundance ratio inferred from these observations with the predictions of chemical models. The OD line is detected in absorption towards the source continuum. This is the first detection of OD outside the solar system. The SOFIA observation, coupled to the observation of the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~ 17-90 in the gas where the absorption takes place. This value is fairly high compared with model predictions. This may be reconciled if reprocessing in the gas by means of the dissociative recombination of H2DO+ further fractionates OH with respect to water. The present observation demonstrates the capability of the SOFIA/GREAT instrument to detect the ground transition of OD towards star-forming regions in a frequency range that was not accessible before. Dissociative recombination of H2DO+ may play an important role in setting a high OD abundance. Measuring the branching ratios of this reaction in the laboratory will be of great value for chemical models.Comment: 6 pages, 6 figures, 3 tables, accepted for publication in A&A SOFIA/GREAT special issu