Mid-Infrared Imaging of NGC 6334 I

We present high-resolution (<0.5") mid-infrared Keck II images of individual sources in the central region of NGC 6334 I. We compare these images to images at a variety of other wavelengths from the near infrared to cm radio continuum and speculate on the nature of the NGC 6334 I sources. We assert that the cometary shape of the UCHII region here, NGC 6334 F, is due to a champagne-like flow from a source on the edge of a molecular clump and not a due to a bow shock caused by the supersonic motion of the UCHII region through the interstellar medium. The mid-infrared emission in concentrated into an arc of dust that define the boundary between the UCHII region and the molecular clump. This dust arc contains a majority of the masers in the region. We discuss the nature of the four near-infrared sources associated with IRS-I 1, and suggest that one of the sources, IRS1E, is responsible for the heating and ionizing of the UCHII region and the mid-infrared dust arc. Infrared source IRS-I 2, which has been thought to be a circumstellar disk associated with a linear distribution of methanol masers, is found not to be directly coincident with the masers and elongated at a much different position angle. IRS-I 3 is found to be a extended source of mid-infrared emission coming from a cluster of young dusty sources seen in the near-infrared.Comment: Accepted for publication by the Astrophysical Journal, 27 pages, 9 figure

The XMM Newton and INTEGRAL observations of the supergiant fast X-ray transient IGR J16328-4726

The accretion mechanism producing the short flares observed from the Supergiant Fast X-ray Transients (SFXT) is still highly debated and forms a major part in our attempts to place these X-ray binaries in the wider context of the High Mass X-ray Binaries. We report on a 216 ks INTEGRAL observation of the SFXT IGR J16328-4726 (August 24-27, 2014) simultaneous with two fixed-time observations with XMM Newton (33ks and 20ks) performed around the putative periastron passage, in order to investigate the accretion regime and the wind properties during this orbital phase. During these observations, the source has shown luminosity variations, from 4x10^{34} erg/s to 10^{36} erg/s, linked to spectral properties changes. The soft X-ray continuum is well modeled by a power law with a photon index varying from 1.2 up to 1.7 and with high values of the column density in the range 2-4x10^{23}/cm^2. We report on the presence of iron lines at 6.8-7.1 keV suggesting that the X-ray flux is produced by accretion of matter from the companion wind characterized by density and temperature inhomogeneities

High-spatial-resolution observations of NH3 and CH3OH towards the massive twin cores NGC6334 I & I(N)

Molecular line observations of NH3 (J,K)=(1,1), (2,2) and CH3OH at 24.93GHz taken with the Australian Telescope Compact Array (ATCA) toward the massive twin cores NGC6334 I & I(N) reveal significant variations in the line emission between the two massive cores. The UCHII region/hot core NGC6334 I exhibits strong thermal NH3 and CH3OH emission adjacent to the UCHII region and coincident with two mm continuum peaks observed by Hunter et al. (in prep.). In contrast, we find neither compact NH3 nor thermal CH3OH line emission toward NGC6334 I(N). There, the NH3 emission is distributed over a broad region (>1') without a clear peak, and we find Class I CH3OH maser emission with peak brightness temperatures up to 7000K. The maser emission peaks appear to be spatially associated with the interfaces between the molecular outflows and the ambient dense gas. Peak NH3(1,1) line brightness temperatures >= 70K in both regions indicate gas temperatures of the same order. NH3 emission is also detected toward the outflow in NGC6334 I resulting in an estimated rotational temperature of Trot~19K. Furthermore, we observe CH3OH and NH3 absorption toward the UCHII region, the velocity structure is consistent with expanding molecular gas around the UCHII region. Thermal and kinematic effects possibly imposed from the UCHII region on the molecular core are also discussed.Comment: Accepted for the Astrophysical Journa

The Detection of Outflows in the IR-Quiet Molecular Core NGC 6334 I(North)

We find strong evidence for outflows originating in the dense molecular core NGC 6334 I(North): a 1000 Msol molecular core distinguished by its lack of HII regions and mid-IR emission. New observations were obtained of the SiO 2-1 and 5-4 lines with the SEST 15-m telescope and the H2 (1-0) S(1) line with the ESO 2.2-m telescope. The line profiles of the SiO transitions show broad wings extending from -50 to 40 km/s, and spatial maps of the line wing emission exhibit a bipolar morphology with the peaks of the red and blue wing separated by 30". The estimated mass loss rate of the outflow is comparable to those for young intermediate to high-mass stars. The near-IR images show eight knots of H2 emission. Five of the knots form a linear chain which is displaced from the axis of the SiO outflow; these knots may trace shock excited gas along the path of a second, highly collimated outflow. We propose that I(N) is a rare example of a molecular core in an early stage of cluster formation.Comment: 4 pages, LaTeX, 3 ps figures, accepted by ApJ

First Detection of Millimeter Dust Emission from Brown Dwarf Disks

We report results from the first deep millimeter continuum survey targeting Brown Dwarfs (BDs). The survey led to the first detection of cold dust in the disks around two young BDs (CFHT-BD-Tau 4 and IC348 613), with deep JCMT and IRAM observations reaching flux levels of a few mJy. The dust masses are estimated to be a few Earth masses assuming the same dust opacities as usually applied to TTauri stars.Comment: 5 pages, accepted for ApJ

Discovery of New Milky Way Star Cluster Candidates in the 2MASS Point Source Catalog II. Physical Properties of the Star Cluster CC01

Three new obscured Milky Way clusters were detected as surface density peaks in the 2MASS point source catalog during our on-going search for hidden globular clusters and massive Arches-like star clusters. One more cluster was discovered serendipitously during a visual inspection of the candidates. The first deep J, H, and Ks imaging of the cluster [IBP2002] CC01 is presented. We estimated a cluster age of ~1-3 Myr, distance modulus of (m-M)0=12.56+-0.08 mag (D=3.5 Kpc), and extinction of AV~7.7 mag. We also derived the initial mass function slope for the cluster: Gamma=-2.23+-0.16. The integration over the initial mass function yielded a total cluster mass M_{total}<=1800+-200Msol. CC01 appears to be a regular, not very massive star cluster, whose formation has probably been induced by the shock front from the nearby HII region Sh2-228.Comment: 8 pages, 9 figures, accepted in A&

The true nature of the alleged planetary nebula W16-185

We report the discovery of a small cluster of massive stars embedded in a NIR nebula in the direction of the IRAS15411-5352 point source, which is related to the alleged planetary nebula W16-185. The majority of the stars present large NIR excess characteristic of young stellar objects and have bright counterparts in the Spitzer IRAC images; the most luminous star (IRS1) is the NIR counterpart of the IRAS source. We found very strong unresolved Brgamma emission at the IRS1 position and more diluted and extended emission across the continuum nebula. From the sizes and electron volume densities we concluded that they represent ultra-compact and compact HII regions, respectively. Comparing the Brgamma emission with the 7 mm free-free emission, we estimated that the visual extinction ranges between 14 and 20 mag. We found that only one star (IRS1) can provide the number of UV photons necessary to ionize the nebula.Comment: 30 pages, 15 figures, 2 tables V3: minor grammatical changes. Figure 4 is available in pdf file. Accepted for publication in AJ, April / 200

Quiescent H2 Emission From Pre-Main Sequence Stars in Chamaeleon I

We report the discovery of quiescent emission from molecular hydrogen gas located in the circumstellar disks of six pre-main sequence stars, including two weak-line T Tauri stars (TTS), and one Herbig AeBe star, in the Chamaeleon I star forming region. For two of these stars, we also place upper limits on the 2->1 S(1)/1->0 S(1) line ratios of 0.4 and 0.5. Of the 11 pre-main sequence sources now known to be sources of quiescent near-infrared hydrogen emission, four possess transitional disks, which suggests that detectable levels of H$_2$ emission and the presence of inner disk holes are correlated. These H$_2$ detections demonstrate that these inner holes are not completely devoid of gas, in agreement with the presence of observable accretion signatures for all four of these stars and the recent detections of [Ne II] emission from three of them. The overlap in [Ne II] and H$_2$ detections hints at a possible correlation between these two features and suggests a shared excitation mechanism of high energy photons. Our models, combined with the kinematic information from the H$_2$ lines, locate the bulk of the emitting gas at a few tens of AU from the stars. We also find a correlation between H$_2$ detections and those targets which possess the largest H$\alpha$ equivalent widths, suggesting a link between accretion activity and quiescent H$_2$ emission. We conclude that quiescent H$_2$ emission from relatively hot gas within the disks of TTS is most likely related to on-going accretion activity, the production of UV photons and/or X-rays, and the evolutionary status of the dust grain populations in the inner disks.Comment: 12 pages, emulateapj, Accepted by Ap