NGF, BDNF, NT3, and NT4 Bothwell, M
Handbook of experimental pharmacology,
2014, Volume:
220
Journal Article
Peer reviewed
The discovery of nerve growth factor (NGF) was a seminal event in history of research in developmental neurobiology. The further discovery that NGF was just one of a family of structurally similar ...growth factors, neurotrophins, provided important insights into the way nerve cells communicate, during development of the nervous system, and in neuroplasticity, memory, and learning in the adult nervous system. Four neurotrophins, NGF, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and neurotrophin-4 (NT4), regulate a wide variety of neural functions, acting upon p75NTR, TrkA, TrkB, and TrkC receptors.
Abstract
We present Atacama Large Millimeter Array C i(1 − 0) (rest frequency 492 GHz) observations for a sample of 13 strongly lensed dusty star-forming galaxies (DSFGs) originally discovered at ...1.4 mm in a blank-field survey by the South Pole Telescope (SPT). We compare these new data with available C i observations from the literature, allowing a study of the interstellar medium (ISM) properties of ∼30 extreme DSFGs spanning a redshift range 2 < z < 5. Using the C i line as a tracer of the molecular ISM, we find a mean molecular gas mass for SPT-DSFGs of 6.6 × 1010 M⊙. This is in tension with gas masses derived via low-J
12CO and dust masses; bringing the estimates into accordance requires either (a) an elevated CO-to-H2 conversion factor for our sample of αCO ∼ 2.5 and a gas-to-dust ratio ∼200, or (b) an high carbon abundance
$X_{\rm C\,\small {I}} \sim 7\times 10^{-5}$
. Using observations of a range of additional atomic and molecular lines (including C i, C iiand multiple transitions of CO), we use a modern photodissociation region code (3d-pdr) to assess the physical conditions (including the density, UV radiation field strength and gas temperature) within the ISM of the DSFGs in our sample. We find that the ISM within our DSFGs is characterized by dense gas permeated by strong UV fields. We note that previous efforts to characterize photodissociation region regions in DSFGs may have significantly under-estimated the density of the ISM. Combined, our analysis suggests that the ISM of extreme dusty starbursts at high redshift consists of dense, carbon-rich gas not directly comparable to the ISM of starbursts in the local Universe.
We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy to date, SPT-S J031132−5823.4 (hereafter ...SPT0311−58), at . SPT0311−58 was discovered via its 1.4 mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an Atacama Large Millimeter/submillimeter Array 3 mm frequency scan that detected CO(6-5), CO(7-6), and (2-1), and subsequently was confirmed by detections of CO(3-2) with the Australia Telescope Compact Array and with APEX. We constrain the properties of the ISM in SPT0311−58 with a radiative transfer analysis of the dust continuum photometry and the CO and line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311−58 is extremely massive, with an intrinsic gas mass of . Its large mass and intense star formation is very rare for a source well into the epoch of reionization.
Recent results have suggested that the well-known mass-metallicity relation has a strong dependence on the star formation rate (SFR), to the extent that a three-dimensional 'fundamental metallicity ...relation' (FMR) exists which links the three parameters with minimal scatter. In this work, we use a sample of 4253 local galaxies observed in atomic hydrogen from the Arecibo Legacy Fast ALFA survey to demonstrate, for the first time, that a similar fundamental relation (the H i FMR) also exists between stellar mass, gas-phase metallicity and H i mass. This latter relation is likely more fundamental, driving the relation between metallicity, SFR and mass. At intermediate masses, the behaviour of the gas FMR is very similar to that expressed via the SFR. However, we find that the dependence of metallicity on H i content persists to the highest stellar masses, in contrast to the 'saturation' of metallicity with SFR. It is interesting to note that the dispersion of the relation is very low at intermediate stellar masses 9 < log (M
*/M) < 11, suggesting that in this range galaxies evolve smoothly, in an equilibrium between gas inflow, outflow and star formation. At high and low stellar masses, the scatter of the relation is significantly higher, suggesting that merging events and/or stochastic accretion and star formation may drive galaxies outside the relation. We also assemble a sample of galaxies observed in CO. However, due to a small sample size, strong selection bias and the influence of a metallicity-dependent CO/H2 conversion factor, the data are insufficient to test any influence of molecular gas on metallicity.
We present C ii observations of 20 strongly lensed dusty star-forming galaxies at 2.1 < z < 5.7 using Atacama Pathfinder EXperiment and Herschel. The sources were selected on their 1.4 mm flux (S
1.4 ...mm > 20 mJy) from the South Pole Telescope (SPT) survey, with far-infrared (FIR) luminosities determined from extensive photometric data. The C ii line is robustly detected in 17 sources, all but one being spectrally resolved. 11 out of 20 sources observed in C ii also have low-J CO detections from Australia Telescope Compact Array. A comparison with mid- and high-J CO lines from Atacama Large Millimeter/submillimeter Array reveals consistent C ii and CO velocity profiles, suggesting that there is little differential lensing between these species. The C ii, low-J CO and FIR data allow us to constrain the properties of the interstellar medium. We find C ii to CO(1–0) luminosity ratios in the SPT sample of 5200 ± 1800, with significantly less scatter than in other samples. This line ratio can be best described by a medium of C ii and CO emitting gas with a higher C ii than CO excitation temperature, high CO optical depth τCO(1–0) ≫ 1, and low to moderate C ii optical depth
$\tau _{{\rm C\,\small {II}}}$
≲ 1. The geometric structure of photodissociation regions allows for such conditions.
ABSTRACT The South Pole Telescope has discovered 100 gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0 5 resolution 870 Atacama Large Millimeter/submillimeter ...Array imaging of a sample of 47 DSFGs spanning , and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies ( ), with a median magnification of , extending to . We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the dust optical depth is unity and find this wavelength to be correlated with the dust temperature. This correlation leads to discrepancies in dust mass estimates of a factor of two compared to estimates using a single value for this wavelength. We investigate the relationship between the C ii line and the far-infrared luminosity and find that the same correlation between the C ii/ ratio and found for low-redshift star-forming galaxies applies to high-redshift galaxies and extends at least two orders of magnitude higher in . This lends further credence to the claim that the compactness of the IR-emitting region is the controlling parameter in establishing the "C ii deficit."
We present the results from a survey of 12CO emission in 40 luminous sub-millimetre galaxies (SMGs), with 850-μm fluxes of S
850 μm = 4-20 mJy, conducted with the Plateau de Bure Interferometer. We ...detect 12CO emission in 32 SMGs at z ∼ 1.2-4.1, including 16 SMGs not previously published. Using multiple 12CO line (J
up = 2-7) observations, we derive a median spectral line energy distribution for luminous SMGs. We report the discovery of a fundamental relationship between 12CO FWHM and 12CO line luminosity in high-redshift starbursts, which we interpret as a natural consequence of the baryon-dominated dynamics within the regions probed by our observations. We use far-infrared luminosities to assess the star formation efficiency in our SMGs, finding that the slope of the L′CO-L
FIR relation is close to linear. We derive molecular gas masses, finding a mean gas mass of (5.3 ± 1.0) × 1010 M. Combining these with dynamical masses, we determine the redshift evolution of the gas content of SMGs, finding that they do not appear to be significantly more gas rich than less vigorously star-forming galaxies at high redshifts. Finally, we collate X-ray observations, and study the interdependence of gas and dynamical properties of SMGs with their AGN activity and supermassive black hole masses (M
BH), finding that SMGs lie significantly below the local M
BH-σ relation.
We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array ...(ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of super(12)CO, CI, and H sub(2)O, we also detect several faint transitions of super(13)CO, HCN, HNC, HCO super(+), and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the super(13)CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which super(13)CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO super(+), and CN is consistent with a warm, dense medium with T sub(kin) ~ 55 K and n sub(H2), gap 10 super(5.5) cm super(-3). High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.
We use the most extensive integral field spectroscopic map of a local galaxy, NGC 628, combined with gas and stellar mass surface density maps, to study the distribution of metals in this galaxy out ...to three effective radii (R
e). At each galactocentric distance, we compute the metal budget and thus constrain the mass of metals lost. We find that in the disc about 50 per cent of the metals have been lost throughout the lifetime of the galaxy. The fraction of metals lost is higher in the bulge (∼70 per cent) and decreases towards the outer disc (∼3 R
e). In contrast to studies based on the gas kinematics, which are only sensitive to ongoing outflow events, our metal budget analysis enables us to infer the average outflow rate during the galaxy lifetime. By using simple physically motivated models of chemical evolution, we can fit the observed metal budget at most radii with an average outflow loading factor of order unity, thus clearly demonstrating the importance of outflows in the evolution of disc galaxies of this mass range (log (M
⋆/M⊙) ∼ 10). The observed gas phase metallicity is higher than expected from the metal budget and suggests late-time accretion of enriched gas, likely raining on to the disc from the metal-enriched halo.
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