1,882 research outputs found
Star formation in galaxies at z~4-5 from the SMUVS survey: a clear starburst/main-sequence bimodality for Halpha emitters on the SFR-M* plane
We study a large galaxy sample from the Spitzer Matching Survey of the
UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6
micron fluxes indicative of strong Halpha emission at z=3.9-4.9. We find that
the percentage of "Halpha excess" sources reaches 37-40% for galaxies with
stellar masses log10(M*/Msun) ~ 9-10, and decreases to <20% at log10(M*/Msun) ~
10.7. At higher stellar masses, however, the trend reverses, although this is
likely due to AGN contamination. We derive star formation rates (SFR) and
specific SFR (sSFR) from the inferred Halpha equivalent widths (EW) of our
"Halpha excess" galaxies. We show, for the first time, that the "Halpha excess"
galaxies clearly have a bimodal distribution on the SFR-M* plane: they lie on
the main sequence of star formation (with log10(sSFR/yr^{-1})<-8.05) or in a
starburst cloud (with log10(sSFR/yr^{-1}) >-7.60). The latter contains ~15% of
all the objects in our sample and accounts for >50% of the cosmic SFR density
at z=3.9-4.9, for which we derive a robust lower limit of 0.066 Msun yr^{-1}
Mpc^{-3}. Finally, we identify an unusual >50sigma overdensity of z=3.9-4.9
galaxies within a 0.20 x 0.20 sq. arcmin region. We conclude that the SMUVS
unique combination of area and depth at mid-IR wavelengths provides an
unprecedented level of statistics and dynamic range which are fundamental to
reveal new aspects of galaxy evolution in the young Universe.Comment: 18 pages, 11 figures, 1 table. Re-submitted to the ApJ, after
addressing referee report. Main changes with respect to v1: a new section and
a new appendix have been added to investigate further the origin and
robustness of the sSFR bimodality. No conclusion change
On stability of the three-dimensional fixed point in a model with three coupling constants from the expansion: Three-loop results
The structure of the renormalization-group flows in a model with three
quartic coupling constants is studied within the -expansion method up
to three-loop order. Twofold degeneracy of the eigenvalue exponents for the
three-dimensionally stable fixed point is observed and the possibility for
powers in to appear in the series is investigated.
Reliability and effectiveness of the -expansion method for the given
model is discussed.Comment: 14 pages, LaTeX, no figures. To be published in Phys. Rev. B, V.57
(1998
Power-law correlations and orientational glass in random-field Heisenberg models
Monte Carlo simulations have been used to study a discretized Heisenberg
ferromagnet (FM) in a random field on simple cubic lattices. The spin variable
on each site is chosen from the twelve [110] directions. The random field has
infinite strength and a random direction on a fraction x of the sites of the
lattice, and is zero on the remaining sites. For x = 0 there are two phase
transitions. At low temperatures there is a [110] FM phase, and at intermediate
temperature there is a [111] FM phase. For x > 0 there is an intermediate phase
between the paramagnet and the ferromagnet, which is characterized by a
|k|^(-3) decay of two-spin correlations, but no true FM order. The [111] FM
phase becomes unstable at a small value of x. At x = 1/8 the [110] FM phase has
disappeared, but the power-law correlated phase survives.Comment: 8 pages, 12 Postscript figure
Keck/HIRES spectroscopy of V838 Monocerotis in October 2005
V838 Mon erupted at the beginning of 2002 becoming an extremely luminous
star. Among various scenarios proposed to explain the nature of the outburst
the most promising is a stellar merger event. In this paper we investigate the
observational properties of the star and its surroundings in the post outburst
phase. We have obtained a high resolution optical spectrum of V838 Mon in
October 2005 using the Keck I telescope.We have identified numerous atomic
features and molecular bands present in the spectrum and provided an atlas of
those features. In order to improve the spectrum interpretation we have
performed simple modeling of the molecular bands. Our analysis indicates that
the spectrum is dominated by molecular absorption features arising in
photospheric regions with temperatures of ~2400 K and in colder outer layers,
where the temperature decreases down to ~500 K. A number of resonance lines of
neutral alkali metals are observed to show P-Cyg profiles. Particularly
interesting are numerous prominent emission lines of [FeII]. All of them show
practically the same profile, which can be well described by a Lorentzian
profile. In the blue part of the spectrum photospheric signatures of the B-type
companion are easily seen. We have fitted the observed spectrum with a
synthetic one and the obtained parameters are consistent with the B3V type. We
have also estimated radial and rotational velocities of the companion.Comment: accepted to ApJS, 21 pages, 15 figures; a paragraph about photometry
has been added, typos corrected
Critical behavior of three-dimensional magnets with complicated ordering from three-loop renormalization-group expansions
The critical behavior of a model describing phase transitions in 3D
antiferromagnets with 2N-component real order parameters is studied within the
renormalization-group (RG) approach. The RG functions are calculated in the
three-loop order and resummed by the generalized Pade-Borel procedure
preserving the specific symmetry properties of the model. An anisotropic stable
fixed point is found to exist in the RG flow diagram for N > 1 and lies near
the Bose fixed point; corresponding critical exponents are close to those of
the XY model. The accuracy of the results obtained is discussed and estimated.Comment: 10 pages, LaTeX, revised version published in Phys. Rev.
The Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS):The Evolution of Dusty and Nondusty Galaxies with Stellar Mass at z = 2–6
The Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS) has obtained the largest ultradeep Spitzer maps to date in a single field of the sky. We considered the sample of about 66,000 SMUVS sources at z = 2–6 to investigate the evolution of dusty and nondusty galaxies with stellar mass through the analysis of the galaxy stellar mass function (GSMF), extending previous analyses about one decade in stellar mass and up to z = 6. We further divide our nondusty galaxy sample with rest-frame optical colors to isolate red quiescent (“passive”) galaxies. At each redshift, we identify a characteristic stellar mass in the GSMF above which dusty galaxies dominate, or are at least as important as nondusty galaxies. Below that stellar mass, nondusty galaxies compose about 80% of all sources, at all redshifts except at z = 4–5. The percentage of dusty galaxies at z = 4–5 is unusually high: 30%–40% for {M}* ={10}9{--}{10}10.5 {M}ȯ and >80% at M * > 1011 M ⊙, which indicates that dust obscuration is of major importance in this cosmic period. The overall percentage of massive ({log}}10({M}* /{M}ȯ )> 10.6) galaxies that are quiescent increases with decreasing redshift, reaching >30% at z ∼ 2. Instead, the quiescent percentage among intermediate-mass galaxies (with {log}}10({M}* /{M}ȯ )=9.7{--}10.6) stays roughly constant at a ∼10% level. Our results indicate that massive and intermediate-mass galaxies clearly have different evolutionary paths in the young universe and are consistent with the scenario of galaxy downsizing
Glutamine addiction promotes glucose oxidation in triple-negative breast cancer
Glutamine is a conditionally essential nutrient for many cancer cells, but it remains unclear how consuming glutamine in excess of growth requirements confers greater fitness to glutamine-addicted cancers. By contrasting two breast cancer subtypes with distinct glutamine dependencies, we show that glutamine-indispensable triple-negative breast cancer (TNBC) cells rely on a non-canonical glutamine-to-glutamate overflow, with glutamine carbon routed once through the TCA cycle. Importantly, this single-pass glutaminolysis increases TCA cycle fluxes and replenishes TCA cycle intermediates in TNBC cells, a process that achieves net oxidation of glucose but not glutamine. The coupling of glucose and glutamine catabolism appears hard-wired via a distinct TNBC gene expression profile biased to strip and then sequester glutamine nitrogen, but hampers the ability of TNBC cells to oxidise glucose when glutamine is limiting. Our results provide a new understanding of how metabolically rigid TNBC cells are sensitive to glutamine deprivation and a way to select vulnerable TNBC subtypes that may be responsive to metabolic-targeted therapies
Stability of a cubic fixed point in three dimensions. Critical exponents for generic N
The detailed analysis of the global structure of the renormalization-group
(RG) flow diagram for a model with isotropic and cubic interactions is carried
out in the framework of the massive field theory directly in three dimensions
(3D) within an assumption of isotropic exchange. Perturbative expansions for RG
functions are calculated for arbitrary up to the four-loop order and
resummed by means of the generalized Pad-Borel-Leroy technique.
Coordinates and stability matrix eigenvalues for the cubic fixed point are
found under the optimal value of the transformation parameter. Critical
dimensionality of the model is proved to be equal to that
agrees well with the estimate obtained on the basis of the five-loop
\ve-expansion [H. Kleinert and V. Schulte-Frohlinde, Phys. Lett. B342, 284
(1995)] resummed by the above method. As a consequence, the cubic fixed point
should be stable in 3D for , and the critical exponents controlling
phase transitions in three-dimensional magnets should belong to the cubic
universality class. The critical behavior of the random Ising model being the
nontrivial particular case of the cubic model when N=0 is also investigated.
For all physical quantities of interest the most accurate numerical estimates
with their error bounds are obtained. The results achieved in the work are
discussed along with the predictions given by other theoretical approaches and
experimental data.Comment: 33 pages, LaTeX, 7 PostScript figures. Final version corrected and
added with an Appendix on the six-loop stud
The critical behavior of frustrated spin models with noncollinear order
We study the critical behavior of frustrated spin models with noncollinear
order, including stacked triangular antiferromagnets and helimagnets. For this
purpose we compute the field-theoretic expansions at fixed dimension to six
loops and determine their large-order behavior. For the physically relevant
cases of two and three components, we show the existence of a new stable fixed
point that corresponds to the conjectured chiral universality class. This
contradicts previous three-loop field-theoretical results but is in agreement
with experiments.Comment: 4 pages, RevTe
Episodic mass loss in binary evolution to the Wolf-Rayet phase: Keck and HST proper motions of RY Scuti's nebula
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for
producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to
account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a
massive binary star caught in this brief but important phase. Its toroidal
nebula indicates equatorial mass loss during RLOF, while the mass-gaining star
is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula
has two components: an inner ionised double-ring system, and an outer dust
torus that is twice the size of the ionised rings. We present two epochs of
Lband Keck NGS-AO images of the dust torus, plus three epochs of HST images of
the ionised gas rings. Proper motions show that the inner ionised rings and the
outer dust torus came from two separate ejection events roughly 130 and 250 yr
ago. This suggests that RLOF in massive contact binaries can be accompanied by
eruptive and episodic burst of mass loss, reminiscent of LBVs. We speculate
that the repeating outbursts may arise in the mass gainer from instabilities
associated with a high accretion rate. If discrete mass-loss episodes in other
RLOF binaries are accompanied by luminous outbursts, they might contribute to
the population of extragalactic optical transients. When RLOF ends for RY
Scuti, the overluminous mass gainer, currently surrounded by an accretion disk,
will probably become a B[e] supergiant and may outshine the hotter mass-donor
star that should die as a Type Ib/c supernova.Comment: 15 pages, 7 figures, submitted to MNRA
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