Chemical modeling of the L1498 and L1517B prestellar cores: CO and HCO+ depletion

Prestellar cores exhibit a strong chemical differentiation, which is mainly caused by the freeze-out of molecules onto the grain surfaces. Understanding this chemical structure is important, because molecular lines are often used as probes to constrain the core physical properties. Here we present new observations and analysis of the C18O (1-0) and H13CO+ (1-0) line emission in the L1498 and L1517B prestellar cores, located in the Taurus-Auriga molecular complex. We model these observations with a detailed chemistry network coupled to a radiative transfer code. Our model successfully reproduces the observed C18O (1-0) emission for a chemical age of a few 10^5 years. On the other hand, the observed H13CO+ (1-0) is reproduced only if cosmic-ray desorption by secondary photons is included, and if the grains have grown to a bigger size than average ISM grains in the core interior. This grain growth is consistent with the infrared scattered light ("coreshine") detected in these two objects, and is found to increase the CO abundance in the core interior by about a factor four. According to our model, CO is depleted by about 2-3 orders of magnitude in the core center.Comment: Accepted for publication in A&

First results from the CALYPSO IRAM-PdBI survey. I. Kinematics of the inner envelope of NGC1333-IRAS2A

The structure and kinematics of Class 0 protostars on scales of a few hundred AU is poorly known. Recent observations have revealed the presence of Keplerian disks with a diameter of 150-180 AU in L1527-IRS and VLA1623A, but it is not clear if such disks are common in Class 0 protostars. Here we present high-angular-resolution observations of two methanol lines in NGC1333-IRAS2A. We argue that these lines probe the inner envelope, and we use them to study the kinematics of this region. Our observations suggest the presence of a marginal velocity gradient normal to the direction of the outflow. However, the position velocity diagrams along the gradient direction appear inconsistent with a Keplerian disk. Instead, we suggest that the emission originates from the infalling and perhaps slowly rotating envelope, around a central protostar of 0.1-0.2 M$_\odot$. If a disk is present, it is smaller than the disk of L1527-IRS, perhaps suggesting that NGC1333-IRAS2A is younger.Comment: Accepted for publication in A&A letter

First results from the CALYPSO IRAM-PdBI survey - III. Monopolar jets driven by a proto-binary system in NGC1333-IRAS2A

Context: The earliest evolutionary stages of low-mass protostars are characterised by hot and fast jets which remove angular momentum from the circumstellar disk, thus allowing mass accretion onto the central object. However, the launch mechanism is still being debated. Aims: We would like to exploit high-angular (~ 0.8") resolution and high-sensitivity images to investigate the origin of protostellar jets using typical molecular tracers of shocked regions, such as SiO and SO. Methods: We mapped the inner 22" of the NGC1333-IRAS2A protostar in SiO(5-4), SO(65-54), and the continuum emission at 1.4 mm using the IRAM Plateau de Bure interferometer in the framework of the CALYPSO IRAM large program. Results: For the first time, we disentangle the NGC1333-IRAS2A Class 0 object into a proto-binary system revealing two protostars (MM1, MM2) separated by ~ 560 AU, each of them driving their own jet, while past work considered a single protostar with a quadrupolar outflow. We reveal (i) a clumpy, fast (up to |V-VLSR| > 50 km/s), and blueshifted jet emerging from the brightest MM1 source, and (ii) a slower redshifted jet, driven by MM2. Silicon monoxide emission is a powerful tracer of high-excitation (Tkin > 100 K; n(H2) > 10^5 cm-3) jets close to the launching region. At the highest velocities, SO appears to mimic SiO tracing the jets, whereas at velocities close to the systemic one, SO is dominated by extended emission, tracing the cavity opened by the jet. Conclusions: Both jets are intrinsically monopolar, and intermittent in time. The dynamical time of the SiO clumps is < 30-90 yr, indicating that one-sided ejections from protostars can take place on these timescales.Comment: Astronomy & Astrophysics Letter, in pres

Multispeckle diffusing-wave spectroscopy: a tool to study slow relaxation and time-dependent dynamics

A multispeckle technique for efficiently measuring correctly ensemble-averaged intensity autocorrelation functions of scattered light from non-ergodic and/or non-stationary systems is described. The method employs a CCD camera as a multispeckle light detector and a computer-based correlator, and permits the simultaneous calculation of up to 500 correlation functions, where each correlation function is started at a different time. The correlation functions are calculated in real time and are referenced to a unique starting time. The multispeckle nature of the CCD camera detector means that a true ensemble average is calculated; no time averaging is necessary. The technique thus provides a "snapshot" of the dynamics, making it particularly useful for non-stationary systems where the dynamics are changing with time. Delay times spanning the range from 1 ms to 1000 s are readily achieved with this method. The technique is demonstrated in the multiple scattering limit where diffusing-wave spectroscopy theory applies. The technique can also be combined with a recently-developed two-cell technique that can measure faster decay times. The combined technique can measure delay times from 10 ns to 1000 s. The method is peculiarly well suited for studying aging processes in soft glassy materials, which exhibit both short and long relaxation times, non-ergodic dynamics, and slowly-evolving transient behavior.Comment: 11 pages 13 figures Accepted in Review of Scientific Instrument (june 02

Glycolaldehyde in Perseus young solar analogs

Aims: In this paper we focus on the occurrence of glycolaldehyde (HCOCH2OH) in young solar analogs by performing the first homogeneous and unbiased study of this molecule in the Class 0 protostars of the nearby Perseus star forming region. Methods: We obtained sub-arcsec angular resolution maps at 1.3mm and 1.4mm of glycolaldehyde emission lines using the IRAM Plateau de Bure (PdB) interferometer in the framework of the CALYPSO IRAM large program. Results: Glycolaldehyde has been detected towards 3 Class 0 and 1 Class I protostars out of the 13 continuum sources targeted in Perseus: NGC1333-IRAS2A1, NGC1333-IRAS4A2, NGC1333-IRAS4B1, and SVS13-A. The NGC1333 star forming region looks particularly glycolaldehyde rich, with a rate of occurrence up to 60%. The glycolaldehyde spatial distribution overlaps with the continuum one, tracing the inner 100 au around the protostar. A large number of lines (up to 18), with upper-level energies Eu from 37 K up to 375 K has been detected. We derived column densities > 10^15 cm^-2 and rotational temperatures Trot between 115 K and 236 K, imaging for the first time hot-corinos around NGC1333-IRAS4B1 and SVS13-A. Conclusions: In multiple systems glycolaldehyde emission is detected only in one component. The case of the SVS13-A+B and IRAS4-A1+A2 systems support that the detection of glycolaldehyde (at least in the present Perseus sample) indicates older protostars (i.e. SVS13-A and IRAS4-A2), evolved enough to develop the hot-corino region (i.e. 100 K in the inner 100 au). However, only two systems do not allow us to firmly conclude whether the primary factor leading to the detection of glycolaldehyde emission is the environments hosting the protostars, evolution (e.g. low value of Lsubmm/Lint), or accretion luminosity (high Lint).Comment: A&A, in pres

In vivo imaging of the central and peripheral effects of sleep deprivation and suprachiasmatic nuclei lesion on PERIOD-2 protein in mice.

STUDY OBJECTIVES: That sleep deprivation increases the brain expression of various clock genes has been well documented. Based on these and other findings we hypothesized that clock genes not only underlie circadian rhythm generation but are also implicated in sleep homeostasis. However, long time lags have been reported between the changes in the clock gene messenger RNA levels and their encoded proteins. It is therefore crucial to establish whether also protein levels increase within the time frame known to activate a homeostatic sleep response. We report on the central and peripheral effects of sleep deprivation on PERIOD-2 (PER2) protein both in intact and suprachiasmatic nuclei-lesioned mice. DESIGN: In vivo and in situ PER2 imaging during baseline, sleep deprivation, and recovery. SETTINGS: Mouse sleep-recording facility. PARTICIPANTS: Per2::Luciferase knock-in mice. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Six-hour sleep deprivation increased PER2 not only in the brain but also in liver and kidney. Remarkably, the effects in the liver outlasted those observed in the brain. Within the brain the increase in PER2 concerned the cerebral cortex mainly, while leaving suprachiasmatic nuclei (SCN) levels unaffected. Against expectation, sleep deprivation did not increase PER2 in the brain of arrhythmic SCN-lesioned mice because of higher PER2 levels in baseline. In contrast, liver PER2 levels did increase in these mice similar to the sham and partially lesioned controls. CONCLUSIONS: Our results stress the importance of considering both sleep-wake dependent and circadian processes when quantifying clock-gene levels. Because sleep deprivation alters PERIOD-2 in the brain as well as in the periphery, it is tempting to speculate that clock genes constitute a common pathway mediating the shared and well-known adverse effects of both chronic sleep loss and disrupted circadian rhythmicity on metabolic health