We report the discovery of a planetary-mass companion, HD 106906 b, with the new Magellan Adaptive Optics (MagAO) + Clio2 system. The companion is detected with Clio2 in three bands: J, K S , and L , and lies at a projected separation of 7. 1 (650 AU). It is confirmed to be comoving with its 13±2 Myr-old F5 host using Hubble Space Telescope/Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr. DUSTY and COND evolutionary models predict the companion's luminosity corresponds to a mass of 11 ± 2 M Jup , making it one of the most widely separated planetary-mass companions known. We classify its Magellan/Folded-Port InfraRed Echellette J/H/K spectrum as L2.5 ± 1; the triangular H-band morphology suggests an intermediate surface gravity. HD 106906 A, a pre-main-sequence Lower Centaurus Crux member, was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy. The disk emission is best fit by a single component at 95 K, corresponding to an inner edge of 15-20 AU and an outer edge of up to 120 AU. If the companion is on an eccentric (e > 0.65) orbit, it could be interacting with the outer edge of the disk. Close-in, planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored. Furthermore, we find no additional companions, though we could detect similar-mass objects at projected separations > 35 AU. In situ formation in a binary-star-like process is more probable, although the companion-to-primary mass ratio, at < 1%, is unusually small. Subject headings: instrumentation: adaptive optics -open clusters and associations: individual (Lower Centaurus Crux) -planet-disk interactions -planetary systems -stars: individual (HD 106906)

We present narrowband WFC3-UVIS and -IR images of four externally irradiated protostellar jets in the Carina nebula: HH 666, HH 901, HH 902, and HH 1066. These massive jets are unusual because they are bathed in UV radiation from dozens of nearby O-type stars, but despite the strong incident ionizing radiation, portions of the jet remain neutral. Near-IR [Fe II] images reveal dense, neutral gas that was not seen in previous studies of Hα emission. We show that near-IR [Fe II] emitting gas must be self-shielded from Lyman continuum photons, regardless of its excitation mechanism (shocks, FUV radiation, or both). High densities are required for the survival of Fe + amid the strong Lyman continuum luminosity from Tr14, raising estimates of the mass-loss rates by an order of magnitude. Higher jet mass-loss rates require higher accretion rates onto their driving protostars, implying that these jets are driven by intermediate-mass (∼ 2 − 8 M ⊙ ) stars. Indeed, the IR driving sources of two of these outflows have luminosities that require intermediate-mass protostars (the other two are so deeply embedded that their luminosity is uncertain). All four of these HH jets are highly collimated, with opening angles of only a few degrees, similar to those observed in low-mass protostars. We propose that these jets reflect essentially the same outflow phenomenon seen in wide-angle molecular outflows associated with intermediate-and high-mass protostars, but that the collimated atomic jet core is irradiated and rendered observable in the harsh radiative environment of the Carina nebula. In more quiescent environments, this atomic core remains invisible, and outflows traced by shock-excited molecules in the outflow cavity give the impression that these outflows have a wider opening angle. Thus, the externally irradiated jets in Carina constitute a new view of collimated jets from intermediate-mass protostars, and offer strong additional evidence that stars up to at least ∼ 8 M ⊙ form by the same accretion mechanisms as low-mass stars.

We analyse eight epochs of Hubble Space Telescope Hα+[N II] imaging of η Carinae's outer ejecta. Proper motions of nearly 800 knots reveal that the detected ejecta are divided into three apparent age groups, dating to around 1250 A.D., to around 1550 A.D., and to during or shortly before the Great Eruption of the 1840s. Ejecta from these groups reside in different locations and provide a firm constraint that η Car experienced multiple major eruptions prior to the nineteenth century. The 1250 and 1550 events did not share the same axisymmetry as the Homunculus; the 1250 event was particularly asymmetric, even one-sided. In addition, the ejecta in the S ridge, which have been associated with the Great Eruption, appear to predate the ejection of the Homunculus by several decades. We detect essentially ballistic expansion across multiple epochs. We find no evidence for large-scale deceleration of the observed knots that could power the soft X-ray shell by ploughing into surrounding material, suggesting that the observed X-rays arise instead from fast, rarefied ejecta from the 1840s overtaking the older dense knots. Early deceleration and subsequent coasting cannot explain the origin of the older outer ejecta -significant episodic mass loss prior to the nineteenth century is required. The time-scale and geometry of the past eruptions provide important constraints for any theoretical physical mechanisms driving η Car's behaviour. Non-repeating mechanisms such as the merger of a close binary in a triple system would require additional complexities to explain the observations.

We present new HST/WFC3-IR narrow-band [Fe II] images of protostellar jets in the Carina Nebula. Combined with five previously published sources, we have a sample of 18 jets and two Herbig-Haro (HH) objects. All of the jets we targeted with Wide-Field Camera 3 (WFC3) show bright infrared [Fe II] emission, and a few Hα candidate jets are confirmed as collimated outflows based on the morphology of their [Fe II] emission. Continuum-subtracted images clearly separate jet emission from the adjacent ionization front, providing a better tracer of the collimated jet than Hα and allowing us to connect these jets with their embedded driving sources. The [Fe II] 1.64 μm/Hα flux ratio measured in the jets is 5 times larger than in the adjacent ionization fronts. The low-ionization jet core requires high densities to shield Fe + against further ionization by the FUV radiation from O-type stars in the H II region. High jet densities imply high mass-loss rates, consistent with the intermediate-mass driving sources we identify for 13 jets. The remaining jets emerge from opaque globules that obscure emission from the protostar. In many respects, the HH jets in Carina look like a scaled-up version of the jets driven by low-mass protostars. Altogether, these observations suggest that [Fe II] emission is a reliable tracer of dense, irradiated jets driven by intermediate-mass protostars. We argue that highly collimated outflows are common to more massive protostars, and that they suggest the outflow physics inferred for low-mass stars formation scales up to at least ∼8 M .

We present a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822 using IRAC and MIPS data obtained from the Spitzer Space Telescope. We find over 500 new YSO candidates in seven massive star-formation regions; these sources were selected using six colour-magnitude cuts. Via spectral energy distribution fitting to the data with YSO radiative transfer models we refine this list, identifying 105 high-confidence and 88 medium-confidence YSO candidates. For these sources we constrain their evolutionary state and estimate their physical properties. The majority of our YSO candidates are massive protostars with an accreting envelope in the initial stages of formation. We fit the mass distribution of the Stage I YSOs with a Kroupa initial mass function and determine a global star-formation rate of 0.039 M yr −1 . This is higher than star-formation rate estimates based on integrated UV fluxes. The new YSO candidates are preferentially located in clusters which correspond to seven active high-mass star-formation regions which are strongly correlated with the 8 and 24 µm emission from PAHs and warm dust. This analysis reveals an embedded high-mass star-formation region, Spitzer I, which hosts the highest number of massive YSO candidates in NGC 6822. The properties of Spitzer I suggest it is younger and more active than the other prominent H ii and star-formation regions in the galaxy.

We report the detection of CO(J = 2 − 1) coincident with the super star cluster (SSC) Mrk 71-A in the nearby Green Pea analog galaxy, NGC 2366. Our NOEMA observations reveal a compact, ∼ 7 pc, molecular cloud whose mass (10 5 M ) is similar to that of the SSC, consistent with a high star-formation efficiency, on the order of 0.5. There are two, spatially distinct components separated by 11 km s −1 . If expanding, these could be due to momentumdriven, stellar wind feedback. Alternatively, we may be seeing the remnant infalling, colliding clouds responsible for triggering the SSC formation. The kinematics are also consistent with a virialized system. These extreme, highdensity, star-forming conditions inhibit energy-driven feedback; the co-spatial existence of a massive, molecular cloud with the SSC supports this scenario, and we quantitatively confirm that any wind-driven feedback in Mrk 71-A is momentum-driven, rather than energy-driven. Since Mrk 71-A is a candidate Lyman continuum emitter, this implies that energy-driven superwinds may not be a necessary condition for the escape of ionizing radiation. In addition, the detection of the nebular continuum emission yields an accurate astrometric position for the Mrk 71-A. We also detect four other massive, molecular clouds in this giant star-forming complex.

We present observations of HCO + and H 13 CO + , N 2 H + , HCS + , HNC and HN 13 C, SO and 34 SO, CCH, SO 2 , and CH 3 OH-E towards a sample of 27 highmass clumps coincident with water maser emission. All transitions are observed with or convolved to nearly identical resolution (30 ′′ ), allowing for intercomparison of the clump properties derived from the mapped transitions. We find N 2 H + emission is spatially differentiated compared to the dust and the other molecules towards a few very luminous cores (10 of 27) and the N 2 H + integrated

We present wide-field, deep narrowband H 2 , Brγ, Hα, [S II], [O III], and broadband I and K-band images of the Carina star formation region. The new images provide a large-scale overview of all the H 2 and Brγ emission present in over a square degree centered on this signature star forming complex. By comparing these images with archival HST and Spitzer images we observe how intense UV radiation from O and B stars affects star formation in molecular clouds. We use the images to locate new candidate outflows and identify the principal shock waves and irradiated interfaces within dozens of distinct areas of star-forming activity. Shocked molecular gas in jets traces the parts of the flow that are most shielded from the intense UV radiation. Combining the H 2 and optical images gives a more complete view of the jets, which are sometimes only visible in H 2 . The Carina region hosts several compact young clusters, and the gas within these clusters is affected by radiation from both the cluster stars and the massive stars nearby. The Carina Nebula is ideal for studying the physics of young H II regions and PDR's, as it contains multiple examples of walls and irradiated pillars at various stages of development. Some of the pillars have detached from their host molecular clouds to form proplyds. Fluorescent H 2 outlines the interfaces between the ionized and molecular gas, and after removing continuum, we detect spatial offsets between the Brγ and H 2 emission along the irradiated interfaces. These spatial offsets can be used to test current models of PDRs once synthetic maps of these lines become available.