3,663 research outputs found
The ALMaQUEST survey – III. Scatter in the resolved star-forming main sequence is primarily due to variations in star formation efficiency
Using a sample of 11,478 spaxels in 34 galaxies with molecular gas, star formation and stellar maps taken from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we investigate the parameters that correlate with variations in star formation rates on kpc scales. We use a combination of correlation statistics and an artificial neural network to quantify the parameters that drive both the absolute star formation rate surface density (Sigma_SFR), as well as its scatter around the resolved star forming main sequence (Delta Sigma_SFR). We find that Sigma_SFR is primarily regulated by molecular gas surface density (Sigma_H2) with a secondary dependence on stellar mass surface density (Sigma_*), as expected from an `extended Kennicutt-Schmidt relation'. However, Delta Sigma_SFR is driven primarily by changes in star formation efficiency (SFE), with variations in gas fraction playing a secondary role. Taken together, our results demonstrate that whilst the absolute rate of star formation is primarily set by the amount of molecular gas, the variation of star formation rate above and below the resolved star forming main sequence (on kpc scales) is primarily due to changes in SFE
The ALMaQUEST Survey: VI. The molecular gas main sequence of `retired' regions in galaxies
In order to investigate the role of gas in the demise of star formation on
kpc-scales, we compare the resolved molecular gas main sequence (rMGMS: Sigma_*
vs Sigma_H2) of star-forming regions to the sequence of `retired' regions that
have ceased to form new stars. Using data from the ALMaQUEST survey, we find
that retired spaxels form a rMGMS that is distinct from that of star-forming
spaxels, offset to lower Sigma_H2 at fixed Sigma_* by a factor of ~5. We study
the rMGMS of star-forming and retired spaxels on a galaxy-by-galaxy basis for
eight individual ALMaQUEST galaxies. Six of these galaxies have their retired
spaxels concentrated within the central few kpc. Molecular gas is detected in
40-100% of retired spaxels in the eight galaxies in our sample. Both the
star-forming and retired rMGMS show a diversity in normalization from
galaxy-to-galaxy. However, in any given galaxy, the rMGMS for retired regions
is found to be distinct from the star-forming sequence and gas fractions of
retired spaxels are up to an order of magnitude lower than the star-forming
spaxels. We conclude that quenching is associated with a depletion (but not
absence) of molecular gas via a mechanism that typically begins in the centre
of the galaxy.Comment: MNRAS, in pres
The influence of defined ante-mortem stressors on the early post-mortem biochemical processes in the abdominal muscle of the Norway lobster, Nephrops norvegicus (Linnaeus, 1758)
The effects of four different ante-mortem stressors (exercise, emersion, starvation and a patent infection with the parasite Hematodinium sp.) on post-mortem processes have been investigated in the abdominal muscle of Norway lobster Nephrops norvegicus by measuring changes in the pH, the levels of glycogen, l-lactate, arginine phosphate, ATP, ADP, AMP, IMP, HxR, Hx and the adenylate energy charge (AEC) over a time course of 24 h with samples being taken at 0, 3, 6, 12 and 24 h. The acute stresses of intense exercise and 2 h emersion resulted in a premature onset of anaerobic glycolysis, leading both to an enhanced glycogen depletion rate and an early accumulation of l-lactate. The chronic stressors, starvation and parasite infection, resulted in a complete ante-mortem depletion of muscle glycogen and consequently the failure of post-mortem glycolytic fermentation. Post-mortem pH and ATP inter-conversion were significantly altered in chronically stressed animals. Ante-mortem, a rapid, almost complete depletion of arginine phosphate was observed in all stress groups. The AEC was altered significantly by all stresses, indicating a strong energy demand. The findings suggest that ante-mortem stressors strongly influence the post-mortem biochemical processes. The laboratory-based results are compared to 'field' data and effects on post-harvest product quality are discussed
GEMS Survey Data and Catalog
We describe the data reduction and object cataloging for the GEMS survey, a large-area (800 arcmin(2)) two-band (F606W and F850LP) imaging survey with the Advanced Camera for Surveys on the Hubble Space Telescope, centered on the Chandra Deep Field-South.STScI HST-GO-9500.01NASA GO-9500, NAS5-26555, NAG5-13063, NAG5-13102European Community’s Human Potential Programunder contractHPRN-CT-2002-00316, HPRN-CT-2002-00305McDonald Observator
The ALMaQUEST Survey - II. What drives central starbursts at z ∼ 0?
Starburst galaxies have elevated star formation rates (SFRs) for their stellar mass. In Ellison et al., we used integral field unit maps of SFR surface density (ΣSFR) and stellar mass surface density (Σ⋆) to show that starburst galaxies in the local universe are driven by SFRs that are preferentially boosted in their central regions. Here, we present molecular gas maps obtained with the Atacama Large Millimeter Array (ALMA) observatory for 12 central starburst galaxies at z ∼ 0 drawn from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The ALMA and MaNGA data are well matched in spatial resolution, such that the ALMA maps of molecular gas surface density (ΣH2) can be directly compared with MaNGA maps at kpc-scale resolution. The combination of ΣH2, Σ⋆ and ΣSFR at the same resolution allow us to investigate whether central starbursts are driven primarily by enhancements in star formation efficiency (SFE) or by increased gas fractions. By computing offsets from the resolved Kennicutt-Schmidt relation (ΣH2 versus ΣSFR) and the molecular gas main sequence (Σ⋆ versus ΣH2), we conclude that the primary driver of the central starburst is an elevated SFE. We also show that the enhancement in ΣSFR is accompanied by a dilution in O/H, consistent with a triggering that is induced by metal poor gas inflow. These observational signatures are found in both undisturbed (9/12 galaxies in our sample) and recently merged galaxies, indicating that both interactions and secular mechanisms contribute to central starbursts
The ALMaQUEST Survey: V. The non-universality of kpc-scale star formation relations and the factors that drive them
Using a sample of ~15,000 kpc-scale star-forming spaxels in 28 galaxies drawn
from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we
investigate the galaxy-to-galaxy variation of the `resolved' Schmidt-Kennicutt
relation (rSK; Sigma_H2 - Sigma_SFR), the `resolved' star forming main sequence
(rSFMS; Sigma_* - Sigma_SFR) and the `resolved' molecular gas main sequence
(rMGMS; Sigma_* - Sigma_H2). The rSK relation, rSFMS and rMGMS all show
significant galaxy-to-galaxy variation in both shape and normalization,
indicating that none of these relations is universal between galaxies. The
rSFMS shows the largest galaxy-to-galaxy variation and the rMGMS the least. By
defining an `offset' from the average relations, we compute a Delta_rSK,
Delta_rSFMS, Delta_rMGMS for each galaxy, to investigate correlations with
global properties. We find the following correlations with at least 2 sigma
significance: the rSK is lower (i.e. lower star formation efficiency) in
galaxies with higher M_*, larger Sersic index and lower specific SFR (sSFR);
the rSFMS is lower (i.e. lower sSFR) in galaxies with higher M_* and larger
Sersic index; the rMGMS is lower (i.e. lower gas fraction) in galaxies with
lower sSFR. In the ensemble of all 15,000 data points, the rSK relation and
rMGMS show equally tight scatters and strong correlation coefficients, compared
with a larger scatter and weaker correlation in the rSFMS. Moreover, whilst
there is no correlation between Delta_rSK and Delta_rMGMS in the sample, the
offset of a galaxy's rSFMS does correlate with both of the other two offsets.
Our results therefore indicate that the rSK and rMGMS are independent
relations, whereas the rSFMS is a result of their combination.Comment: MNRAS, in pres
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