75 research outputs found
A deep dive into NGC 604 with Gemini/NIRI imaging
The giant HII region NGC 604 constitutes a complex and rich population to
studying detail many aspects of massive star formation, such as their
environments and physical conditions, the evolutionary processes involved, the
initial mass function for massive stars and star-formation rates, among many
others. Here, we present our first results of a near-infrared study of NGC 604
performed with NIRI images obtained with Gemini North. Based on deep JHK
photometry, 164 sources showing infrared excess were detected, pointing to the
places where we should look for star-formation processes currently taking
place. In addition, the color-color diagram reveals a great number of objects
that could be giant/supergiant stars or unresolved, small, tight clusters. A
extinction map obtained based on narrow-band images is also shown.Comment: 4 pages, 4 figures. To appear in the proceedings of IAU Symposium
266, Star Clusters: Basic Galactic Building Blocks Throughout Time and Space,
eds. R. de Grijs and J. Lepin
Implications of the kinematical structure of circumnuclear star-forming regions on their derived properties
[Abbreviated] We review the results of high dispersion spectroscopy of 17
circumnuclear starforming regions (CNSFRs) in 3 nearby early spiral galaxies,
NGC2903, NGC3310 and NGC3351. We find that single Gaussian fitting to the
H and [OIII]5007A line profiles results in velocity dispersions around
32km/s and 52km/s, respectively, while the IR CaII triplet cross-correlation
technique provides stellar velocity dispersion values close to 50km/s. Even
though multiple kinematical components are present, the relation between gas
velocity dispersion and Balmer emission line luminosity (L-sigma relation)
reproduces the correlation for disk giant HII regions albeit with a larger
scatter. The scatter in the L-sigma relation is considerably reduced when
theoretical evolutionary corrections are applied suggesting that an age range
is present in the sample of CNSFRs. To analyse the observed complex profiles,
we performed multiple Gaussian component fits to the Hbeta and [OIII]?5007A
lines obtaining optimal fits with two Gaussians of different width. These best
fits indicate that the narrower component has average velocity dispersion close
to 23km/s while the broader component shows average values in the range
50-60km/s for both lines, close to the observed stellar velocity dispersions.
The fluxes of the broad and narrow Hbeta components are similar. This is not
the case for [OIII]5007A for which the broad components have higher fluxes than
the narrow ones, thus producing a clear segregation in their [OIII]/Hbeta
ratios. We suggest a possible scenario for understanding the behaviour of
CNSFRs in the L-sigma and sigma_gas-sigma_star diagrams involving an inner
gaseous disk responsible for the narrow component of the emission lines.Comment: 14 pages, 10 figures, accepted by MNRA
Unveiling the new generation of stars in NGC 604 with Gemini-NIRI
We present a near infrared study focused on the detection and
characterization of the youngest stellar component of the NGC 604 giant
star-forming region, in the Triangulum galaxy (M 33). By means of color-color
diagrams derived from the photometry of JHKs images taken with Gemini-NIRI, we
have found 68 candidate massive young stellar objects. The spatial distribution
of these sources matches the areas where previous studies suggested that star
formation might be taking place, and the high spatial resolution of our deep
NIRI imaging allows to pinpoint the star-forming knots. An analysis of the
fraction of objects that show infrared excess suggests that the star formation
is still active, supporting the presence of a second generation of stars being
born, although the evidence for or against sequential star formation does not
seem to be conclusive.Comment: Article accepted for publication in The Astronomical Journal. 19
pages, 12 figures, 5 table
Interleukin-1 receptor associated kinase 1/4 and bromodomain and extra-terminal inhibitions converge on NF-κB blockade and display synergistic antitumoral activity in activated B-cell subset of diffuse large B-cell lymphoma with <i>MYD88</i> L265P mutation
Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud
We present a spectroscopic study of the N159/N160 massive-star forming region
south of 30 Doradus in the Large Magellanic Cloud, classifying a total of 189
stars in the field of the complex. Most of them belong to O and early B
spectral classes; we have also found some uncommon and very interesting
spectra, including members of the Onfp class, a Be P Cygni star, and some
possible multiple systems. Using spectral types as broad indicators of
evolutionary stages, we considered the evolutionary status of the region as a
whole. We infer that massive stars at different evolutionary stages are present
throughout the region, favoring the idea of a common time for the origin of
recent star formation in the N159/N160 complex as a whole, while sequential
star formation at different rates is probably present in several subregions.Comment: 36 pages, 24 figures (127 spectra mostly OB stars, 4 field images).
Published in The Astronomical Journa
Efficacy and Safety of Liraglutide Versus Placebo as Add-on to Glucose-Lowering Therapy in Patients With Type 2 Diabetes and Moderate Renal Impairment (LIRA-RENAL): A Randomized Clinical Trial
An HST/NICMOS view of the prototypical giant HII region NGC604 in M33
We present the first high-spatial resolution near-infrared (NIR) imaging of
NGC 604, obtained with the NICMOS camera aboard the Hubble Space Telescope
(HST). These NICMOS broadband images reveal new NIR point sources, clusters,
and diffuse structures. We found an excellent spatial correlation between the
8.4 GHz radio continuum and the 2.2mu-m nebular emission. Moreover, massive
young stellar object candidates appear aligned with these radio peaks,
reinforcing the idea that those areas are star-forming regions. Three different
scaled OB associations are recognized in the NICMOS images. The brightest NIR
sources in our images have properties that suggest that they are red supergiant
stars, of which one of them was previously known. This preliminary analysis of
the NICMOS images shows the complexity of the stellar content of the NGC 604
nebula.Comment: Paper presented in the Workshop "Young massive star clusters: initial
conditions and environments" (Granada, Spain - Sept 2007). Astrophysics &
Space Science in press, 7 pages, 4 figure
Very large telescope and Hubble Space Telescope observations of the host galaxy of GRB 990705
We present Very Large Telescope spectroscopic observations of the GRB 990705 host galaxy and highlight the benefits provided by the prompt phase features of gamma-ray bursts (GRBs) to derive the redshifts of the latter. In the host spectrum, we indeed detect an emission feature that we attribute to the [O II] λλ3726, 3729 doublet and derive an unambiguous redshift z = 0.8424 ± 0.0002 for this galaxy. This is in full agreement with the value z ∼ 0.86 ± 0.17 previously derived using a transient absorption edge discovered in the X-ray spectrum of GRB 990705. This burst is therefore the first GRB for which a reliable redshift was derived from the prompt phase emission itself, as opposed to redshift determinations performed using putative host galaxy emission lines or interstellar absorption lines in the GRB afterglows. Deep and high-resolution images of the host of GRB 990705 with the Space Telescope Imaging Spectrograph camera on board the Hubble Space Telescope reveal that the burst occurred in a nearly face-on Sc spiral galaxy typical of disk-dominated systems at 0.75 ≤ z ≤ 1. Assuming a cosmology with H0 = 65 km s-1 Mpc-1, Ωm = 0.3, and Ωλ = 0.7, we derive an absolute B magnitude MB = -21.75 for this galaxy and a star formation rate SFR ≈ 5-8 M⊙ yr-1. Finally, we discuss the implications of using X-ray transient features to derive GRB redshifts with larger burst samples and especially examine the case of short and dark long GRBs.Facultad de Ciencias Astronómicas y Geofísica
Very large telescope and Hubble Space Telescope observations of the host galaxy of GRB 990705
We present Very Large Telescope spectroscopic observations of the GRB 990705 host galaxy and highlight the benefits provided by the prompt phase features of gamma-ray bursts (GRBs) to derive the redshifts of the latter. In the host spectrum, we indeed detect an emission feature that we attribute to the [O II] λλ3726, 3729 doublet and derive an unambiguous redshift z = 0.8424 ± 0.0002 for this galaxy. This is in full agreement with the value z ∼ 0.86 ± 0.17 previously derived using a transient absorption edge discovered in the X-ray spectrum of GRB 990705. This burst is therefore the first GRB for which a reliable redshift was derived from the prompt phase emission itself, as opposed to redshift determinations performed using putative host galaxy emission lines or interstellar absorption lines in the GRB afterglows. Deep and high-resolution images of the host of GRB 990705 with the Space Telescope Imaging Spectrograph camera on board the Hubble Space Telescope reveal that the burst occurred in a nearly face-on Sc spiral galaxy typical of disk-dominated systems at 0.75 ≤ z ≤ 1. Assuming a cosmology with H0 = 65 km s-1 Mpc-1, Ωm = 0.3, and Ωλ = 0.7, we derive an absolute B magnitude MB = -21.75 for this galaxy and a star formation rate SFR ≈ 5-8 M⊙ yr-1. Finally, we discuss the implications of using X-ray transient features to derive GRB redshifts with larger burst samples and especially examine the case of short and dark long GRBs.Facultad de Ciencias Astronómicas y Geofísica
The Onfp Class in the Magellanic Clouds
The Onfp class of rotationally broadened, hot spectra was defined some time
ago in the Galaxy, where its membership to date numbers only eight. The
principal defining characteristic is a broad, centrally reversed He II
4686 emission profile; other emission and absorption lines are also
rotationally broadened. Recent surveys in the Magellanic Clouds (MCs) have
brought the class membership there, including some related spectra, to 28. We
present a survey of the spectral morphology and rotational velocities, as a
first step toward elucidating the nature of this class. Evolved, rapidly
rotating hot stars are not expected theoretically, because the stellar winds
should brake the rotation. Luminosity classification of these spectra is not
possible, because the principal criterion (He II 4686) is peculiar;
however, the MCs provide reliable absolute magnitudes, which show that they
span the entire range from dwarfs to supergiants. The Onfp line-broadening
distribution is distinct and shifted toward larger values from those of normal
O dwarfs and supergiants with >99.99% confidence. All cases with multiple
observations show line-profile variations, which even remove some objects from
the class temporarily. Some of them are spectroscopic binaries; it is possible
that the peculiar profiles may have multiple causes among different objects.
The origin and future of these stars are intriguing; for instance, they could
be stellar mergers and/or gamma-ray-burst progenitors.Comment: 27 pages, 8 figures, 2 tables; AJ accepte
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