Deep Near-Infrared Observations of L1014: Revealing the nature of the core and its embedded source

Recently, the Spitzer Space Telescope discovered L1014-IRS, a mid-infrared source with protostellar colors, toward the heretofore "starless" core L1014. We present deep near-infrared observations that show a scattered light nebula extending from L1014-IRS. This nebula resembles those typically associated with protostars and young stellar objects, tracing envelope cavities presumably evacuated by an outflow. The northern lobe of the nebula has an opening angle of ~100 degrees, while the southern lobe is barely detected. Its morphology suggests that the bipolar cavity and inferred protostellar disk is not inclined more than 30 degrees from an edge-on orientation. The nebula extends at least 8" from the source at Ks, strongly suggesting that L1014-IRS is embedded within L1014 at a distance of 200 pc rather than in a more distant cloud associated with the Perseus arm at 2.6 kpc. In this case, the apparently low luminosity of L1014-IRS, 0.090 Lsun, is consistent with it having a substellar mass. However, if L1014-IRS is obscured by a circumstellar disk, its luminosity and inferred mass may be greater. Using near-infrared colors of background stars, we investigate characteristics of the L1014 molecular cloud core. We determine a mass of 3.6 Msun for regions of the core with Av > 2 magnitudes. A comparison of the radial extinction profile of L1014 with other cores suggests that L1014 may be among the most centrally condensed cores known, perhaps indicative of the earliest stages of brown dwarf or star formation processes.Comment: Replacement includes revision to mass of core. 22 pages, 6 figures. Accepted by Ap

Discovery of a Dusty Ring in the Coalsack: A Dense Core Caught in the Act of Formation?

We present a new infrared extinction study of Globule 2, the most opaque molecular cloud core in the Coalsack complex. Using deep near-infrared imaging observations obtained with the ESO NTT we are able to examine the structure of the globule in significantly greater detail than previously possible. We find the most prominent structural feature of this globule to be a strong central ring of dust column density which was not evident in lower resolution studies of this cloud. This ring represents a region of high density and pressure that is likely a transient structure. For a spherical cloud geometry the ring would correspond to a dense inner shell of high pressure that could not be in dynamical equilibrium with its surroundings since there appear to be no sources of pressure in the central regions of the cloud that could support the shell against gravity and prevent its inward implosion. The timescale for the inward collapse of the ring would be less than 2 x 10^5 years, suggesting that this globule is in an extremely early stage of evolution, and perhaps caught in the process of forming a centrally condensed dense core or Bok globule. Outside its central regions the globule displays a well-behaved density profile whose shape is very similar to that of a stable Bonnor-Ebert sphere. Using SEST we also obtained a C18O spectrum toward the center of the cloud. The CO observation indicates that the globule is a gravitationally bound object. Analysis of the CO line profile reveals significant non-thermal gas motions likely due to turbulence. As a whole the globule may be evolving to a global state of quasi-static dynamical equilibrium in which thermal and turbulent pressure balance gravity.Comment: Contains 21 pages and 5 figures. Due to space limitations in astroph, figures 1, 3 & 5 are submitted as separate .jpg files. Full resolution figures and text can be downloaded from http://cfa-www.harvard.edu/~clada/preprints.htm

Starspots Found on the Ellipsoidal Variable V350 Lacertae = HR 8575

It has been a puzzle why this chromospherically active, strong-dynamo K2 IV-III star is not known to have the large starspots characteristic of other such stars. Published individual radial velocities, which had never been analyzed, are used to derive an orbital solution. Combined with the one older existing orbital solution, this yields an improved orbital ephemeris: time of conjunction (K star behind) = JD 2445255.47 +/- 0.11 days and period = 17.75346 +/- 0.00016 days. All available photoelectric photometry, from 1970.9 to 1992.5, is collected A cos 2 theta fit of the ellipticity effect yields JD 2445255.60 +/- 0.06 days for a time of conjunction, 17.7523 +/- 0.0005 days for the period, and 0.084 mins for the peak-to-peak amplitude in V. With the ellipticity effect removed, the light curve does show measurable starspot variability in 15 of 16 data groups, the starspot wave amplitudes ranging between 0.03 mins and 0.08 mins. Ten starspots are identified and their rotation periods determined, the mean being 17.70 +/- 0.03 days (confirming synchronous rotation) and the range being Delta P/P = 0.017 +/- 0.006 (indicating differential rotation). There is a slow variation in mean brightness, almost 0.1 min in range and at least 2 decades in length

Mitochondria in Developmental and Adult Neurogenesis.

International audienceGeneration of new neurons is a tightly regulated process that involves several intrinsic and extrinsic factors. Among them, a metabolic switch from glycolysis to oxidative phosphorylation, together with mitochondrial remodeling, has emerged as crucial actors of neurogenesis. However, although accumulating data raise the importance of mitochondrial morphology and function in neural stem cell proliferation and differentiation during development, information regarding the contribution of mitochondria to adult neurogenesis processes remains limited. In the present review, we discuss recent evidence covering the importance of mitochondrial morphology, function, and energy metabolism in the regulation of neuronal development and adult neurogenesis, and their impact on memory processes