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Spectrophotometric distances in the K band have been reported by different authors for a number of obscured Galactic HII regions. Almost 50% of them show large discrepancies compared to the classical method using radial velocities measured in the radio spectral region. In order to provide a crucial test of both methods, we selected a target which does not present particular difficulty for any method and which has been measured by as many techniques as possible. The W3 star forming complex, located in the Perseus arm, offers a splendid opportunity for such a task. We used the NIFS spectrograph on the Frederick C. Gillett Gemini North telescope to classify candidate "naked photosphere" OB stars based on 2MASS photometry. Two of the targets are revealed to be mid O-type main sequence stars leading to a distance of d = 2.20 kpc. This is in excellent agreement with the spectrophotometric distance derived in the optical band (d = 2.18 kpc, Humphreys 1978) and with a measurement of the W3 trigonometric parallax (d = 1.95 kpc, Xu et al. 2006). Such results confirm that the spectrophotometric distances in the K band are reliable. The radio derived kinematic distance, on the contrary, gives a distance twice as large (d = 4.2 kpc, Russeil 2003). This indicates that this region of Perseus arm does not follow the Galactic rotation curve, and this may be the case also for other HII regions for which discrepancies have been found.

We present a near infrared study of the stellar content of 35 H\,{\sc{ii}} regions in the Galactic plane. In this work, we have used the near infrared domain $J-$, $H-$ and $K_{s}-$ band color images to visually inspect the sample. Also, color-color and color-magnitude diagrams were used to indicate ionizing star candidates, as well as, the presence of young stellar objects such as classical TTauri Stars (CTTS) and massive young stellar objects (MYSOs). We have obtained {\it Spitzer} IRAC images for each region to help further characterize them. {\it Spitzer} and near infrared morphology to place each cluster in an evolutionary phase of development. {\it Spitzer} photometry was also used to classify the MYSOs. Comparison of the main sequence in color-magnitude diagrams to each observed cluster was used to infer whether or not the cluster kinematic distance is consistent with brightnesses of the stellar sources. We find qualitative agreement for a dozen of the regions, but about half the regions have near infrared photometry that suggests they may be closer than the kinematic distance. A significant fraction of these already have spectrophotometric parallaxes which support smaller distances. These discrepancies between kinematic and spectrophotometric distances are not due to the spectrophotometric methodologies, since independent non-kinematic measurements are in agreement with the spectrophotometric results. For instance, trigonometric parallaxes of star-forming regions were collected from the literature and show the same effect of smaller distances when compared to the kinematic results. In our sample of H\,{\sc{ii}} regions, most of the clusters are evident in the near infrared images. Finally, it is possible to distinguish among qualitative evolutionary stages for these objects., Comment: 59 pages, 146 figures and 4 tables. MNRAS accepted

We discuss the capability of AKARI in recovering diffuse far-infrared emission, and examine the achieved reliability. Critical issues in making images of diffuse emission are the transient response and long-term stability of the far-infrared detectors. Quantitative evaluation of these characteristics are the key to achieving sensitivity comparable to or better than that for point sources (< 20 -- 95 MJy sr-1). We describe current activity and progress toward the production of high quality images of the diffuse far-infrared emission using the AKARI all-sky survey data., Comment: 4 pages, 8 figures, to appear in the Proceedings of the Conference "AKARI, a light to illuminate the misty Universe", Fukutake Hall, The University of Tokyo, Japan, 16-19 February 2009

We present $K$-band spectra of the near infrared counterparts to IRS2E and IRS2W which is associated with the ultracompact HII region W51d, both of them embedded sources in the Galactic compact HII region W51 IRS2. The high spatial resolution observations were obtained with the laser guide star facility and Near infrared Integral Field Spectrograph (NIFS) mounted at the Gemini North observatory. The spectrum of the ionizing source of W51d shows the photospheric features NIII (21155 \AA) in emission and HeII (21897 \AA) in absorption which lead us to classify it as an young O3 type star. We detected CO overtone in emission at 23000 \AA in the spectrum of IRS2E, suggesting that it is a massive young object still surrounded by an accretion disc, probably transitioning from the hot core phase to an ultracompact HII region., Comment: Accepted by ApJ Letters

We present K-band spectra of newly born OB stars in the obscured Galactic giant H II region W51A and ~ 0.8'' angular resolution images in the J, H and K_S-bands. Four objects have been spectroscopically classified as O-type stars. The mean spectroscopic parallax of the four stars gives a distance of 2.0 \pm 0.3 kpc (error in the mean), significantly smaller than the radio recombination line kinematic value of 5.5 kpc or the values derived from maser propermotion observations (6--8 kpc). The number of Lyman continuum photons from the contribution of all massive stars (NLyc ~ 1.5 x 10^{50} s^{-1}) is in good agreement with that inferred from radio recombination lines (NLyc = 1.3 x 10^{50} s^{-1}) after accounting for the smaller distance derived here. We present analysis of archival high angular resolution images (NAOS CONICA at VLT and T-ReCS at Gemini) of the compact region W51 IRS2. The K_S--band images resolve the infrared source IRS~2 indicating that it is a very young compact HII region. Sources IRS2E was resolved into compact cluster (within 660 AU of projected distance) of 3 objects, but one of them is just bright extended emission. W51d1 and W51d2 were identified with compact clusters of 3 objects (maybe 4 in the case of W51d1) each one. Although IRS~2E is the brightest source in the K-band and at 12.6 \micron, it is not clearly associated with a radio continuum source. Our spectrum of IRS~2E shows, similar to previous work, strong emission in Br$\gamma$ and HeI, as well as three forbidden emission lines of FeIII and emission lines of molecular hydrogen (H_2) marking it as a massive young stellar object., Comment: 31 pages and 9 figures, submitted to AJ

AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from the mid- to far-infrared. The instruments also have the capability for imaging and spectroscopy in the wavelength range 2 - 180 micron in the pointed observation mode, occasionally inserted into the continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90 percent of the whole sky with higher spatial resolution and wider wavelength coverage than that of the previous IRAS all-sky survey. Point source catalogues of the All-Sky Survey will be released to the astronomical community. The pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission., Comment: 13 pages, 4 figures, and 3 tables. Accepted for publication in the AKARI special issue of the Publications of the Astronomical Society of Japan

In 2000, Lamb and Reichart predicted that gamma-ray bursts (GRBs) and their afterglows occur in sufficient numbers and at sufficient brightnesses at very high redshifts (z > 5) to eventually replace quasars as the preferred probe of element formation and reionization in the early universe and to be used to characterize the star-formation history of the early universe, perhaps back to when the first stars formed. Here we report the discovery of the afterglow of GRB 050904 and the identification of GRB 050904 as the first very high redshift GRB. We measure its redshift to be 6.39(+0.11,-0.12), which is consistent with the reported spectroscopic redshift (6.29 +/- 0.01). Furthermore, just redward of Ly-alpha the flux is suppressed by a factor of three on the first night, but returns to expected levels by the fourth night. We propose that this is due to absorption by molecular hydrogen that was excited to rovibrational states by the GRB's prompt emission, but was then overtaken by the jet. Now that very high redshift GRBs have been shown to exist, and at least in this case the afterglow was very bright, observing programs that are designed to capitalize on this science will likely drive a new era of study of the early universe, using GRBs as probes., Comment: Submitted to Nature, 11 pages, 3 figures, LaTeX

We present high angular resolution near--infrared images of the obscured Galactic Giant HII (GHII) region G333.1--0.4 in which we detect an OB star cluster. For G333.1--0.4, we find OB stars and other massive objects in very early evolutionary stages, possibly still accreting. We obtained $K$--band spectra of three stars; two show O type photospheric features, while the third has no photospheric features but does show CO 2.3 $\mu$m band--head emission. This object is at least as hot as an early B type star based on its intrinsic luminosity and is surrounded by a circumstellar disc/envelope which produces near infrared excess emission. A number of other relatively bright cluster members also display excess emission in the $K$--band, indicative of disks/envelopes around young massive stars. Based upon the O star photometry and spectroscopy, the distance to the cluster is 2.6 $\pm$ 0.4 kpc, similar to a recently derived kinematic (near side) value. The slope of the $K$--band luminosity function is similar to those found in other young clusters. The mass function slope is more uncertain, and we find $-1.3 \pm 0.2 < \Gamma < -1.1 \pm 0.2$- for stars with M $> 5$ M$_\odot$ where the upper an lower limits are calculated independently for different assumptions regarding the excess emission of the individual massive stars. The number of Lyman continuum photons derived from the contribution of all massive stars in the cluster is 0.2 $\times$ $10^{50}$ $s^{-1}$ $< NLyc < 1.9$ $\times$ $10^{50}$ $s^{-1}$. The integrated cluster mass is 1.0 $\times$ $10^{3}$ $M_\odot < M_{cluster} < 1.3$ $\times$ $10^{3}$ $M_\odot$., Comment: 31 pages, including 12 figures and 3 tables. Accepted for publication in the AJ

We present deep, high angular resolution near-infrared images of the obscured Galactic Giant H II region NGC3576. Our images reach objects to ~3M_sun. We collected high signal-to-noise K-band spectra of eight of the brightest objects, some of which are affected by excess emission and some which follow a normal interstellar reddening law. None of them displayed photospheric features typical of massive OB type stars. This indicates that they are still enshrouded in their natal cocoons. The K-band brightest source (NGC3576 #48) shows CO 2.3 micron bandhead emission, and three others have the same CO feature in absorption. Three sources display spatially unresolved H_2 emission, suggesting dense shocked regions close to the stars. We conclude that the remarkable object NGC3576 #48 is an early-B/late-O star surrounded by a thick circumstellar disk. A number of other relatively bright cluster members also display excess emission in the K-band, indicative of reprocessing disks around massive stars (YSOs). Such emission appears common in other Galactic Giant H II regions we have surveyed. The IMF slope of the cluster, Gamma = -1.51, is consistent with Salpeter's distribution and similar to what has been observed in the Magellanic Cloud clusters and in the periphery of our Galaxy., Comment: 14 pages, 11 figures, accepted for publication in AJ