ABSTRACT
The low-J rotational transitions of 12CO are commonly used to trace the distribution of molecular gas in galaxies. Their ratios are sensitive to excitation and physical conditions in the ...molecular gas. Spatially resolved studies of CO ratios are still sparse and affected by flux calibration uncertainties, especially since most do not have high angular resolution or do not have short-spacing information and hence miss any diffuse emission. We compare the low-J CO ratios across the disc of two massive, star-forming spiral galaxies NGC 2903 and NGC 3627 to investigate whether and how local environments drive excitation variations at GMC scales. We use Atacama Large Millimeter Array (ALMA) observations of the three lowest-J CO transitions at a common angular resolution of 4 arcsec (190 pc). We measure median line ratios of $R_{21}=0.67^{+0.13}_{-0.11}$, $R_{32}=0.33^{+0.09}_{-0.08}$, and $R_{31}=0.24^{+0.10}_{-0.09}$ across the full disc of NGC 3627. We see clear CO line ratio variation across the galaxy consistent with changes in temperature and density of the molecular gas. In particular, towards the centre, R21, R32, and R31 increase by 35 per cent, 50 per cent, and 66 per cent, respectively, compared to their average disc values. The overall line ratio trends suggest that CO(3–2) is more sensitive to changes in the excitation conditions than the two lower J transitions. Furthermore, we find a similar radial R32 trend in NGC 2903, albeit a larger disc-wide average of $\langle R_{32}\rangle =0.47^{+0.14}_{-0.08}$. We conclude that the CO low-J line ratios vary across environments in such a way that they can trace changes in the molecular gas conditions, with the main driver being changes in temperature.
Nitrogen hydrides such as NH
3
and N
2
H
+
are widely used by Galactic observers to trace the cold dense regions of the interstellar medium. In external galaxies, because of limited sensitivity, HCN ...has become the most common tracer of dense gas over large parts of galaxies. We provide the first systematic measurements of N
2
H
+
(1-0) across different environments of an external spiral galaxy, NGC 6946. We find a strong correlation (
r
> 0.98,
p
< 0.01) between the HCN (1-0) and N
2
H
+
(1-0) intensities across the inner ∼8 kpc of the galaxy, at kiloparsec scales. This correlation is equally strong between the ratios N
2
H
+
(1-0)/CO (1-0) and HCN (1-0)/CO (1-0), tracers of dense gas fractions (
f
dense
). We measure an average intensity ratio of N
2
H
+
(1-0)/HCN (1-0) = 0.15 ± 0.02 over our set of five IRAM-30m pointings. These trends are further supported by existing measurements for Galactic and extragalactic sources. This narrow distribution in the average ratio suggests that the observed systematic trends found in kiloparsec-scale extragalactic studies of
f
dense
and the efficiency of dense gas (SFE
dense
) would not change if we employed N
2
H
+
(1-0) as a more direct tracer of dense gas. At kiloparsec scales our results indicate that the HCN (1-0) emission can be used to predict the expected N
2
H
+
(1-0) over those regions. Our results suggest that, even if HCN (1-0) and N
2
H
+
(1-0) trace different density regimes within molecular clouds, subcloud differences average out at kiloparsec scales, yielding the two tracers proportional to each other.
We present new HCN and HCO
+
(
J
= 3–2) images of the nearby star-forming galaxies (SFGs) NGC 3351, NGC 3627, and NGC 4321. The observations, obtained with the Morita ALMA Compact Array, have a ...spatial resolution of ∼290–440 pc and resolve the inner
R
gal
≲ 0.6–1 kpc of the targets, as well as the southern bar end of NGC 3627. We complement this data set with publicly available images of lower excitation lines of HCN, HCO
+
, and CO and analyse the behaviour of a representative set of line ratios: HCN(3–2)/HCN(1–0), HCN(3–2)/HCO
+
(3–2), HCN(1–0)/CO(2–1), and HCN(3–2)/CO(2–1). Most of these ratios peak at the galaxy centres and decrease outwards. We compare the HCN and HCO
+
observations with a grid of one-phase, non-local thermodynamic equilibrium (non-LTE) radiative transfer models and find them compatible with models that predict subthermally excited and optically thick lines. We study the systematic variations of the line ratios across the targets as a function of the stellar surface density (Σ
star
), the intensity-weighted CO(2–1) (⟨
I
CO
⟩), and the star formation rate surface density (Σ
SFR
). We find no apparent correlation with Σ
SFR
, but positive correlations with the other two parameters, which are stronger in the case of ⟨
I
CO
⟩. The HCN/CO–⟨
I
CO
⟩ relations show ≲0.3 dex galaxy-to-galaxy offsets, with HCN(3–2)/CO(2–1)–⟨
I
CO
⟩ being ∼2 times steeper than HCN(1–0)/CO(2–1). In contrast, the HCN(3–2)/HCN(1–0)–⟨
I
CO
⟩ relation exhibits a tighter alignment between galaxies. We conclude that the overall behaviour of the line ratios cannot be ascribed to variations in a single excitation parameter (e.g., density or temperature).
The transport of gas towards the centre of galaxies is critical for black hole feeding and, indirectly, it can control active galactic nucleus (AGN) feedback. We have quantified the molecular gas ...inflow in the central R< 1 kpc of M 51 to be 1 M⊙/yr, using a new gravitational torque map and the molecular gas traced by the Plateau de Bure Interferometer Arcsecond Whirlpool Survey (PAWS). The nuclear stellar bar is responsible for this gas inflow. We also used torque profiles to estimate the location of dynamical resonances, and the results suggest a corotation for the bar CRbar ~ 20′′, and a corotation for the spiral CRsp ~ 100′′. We demonstrate how important it is to correct 3.6 μm images for dust emission when gravitational torques are to be computed, and we examine further sources of uncertainty. Our observational measurement of gas inflow can be compared with nuclear molecular outflow rates and provide useful constraints for numerical simulations.
ABSTRACT
Both the CO(2–1) and CO(1–0) lines are used to trace the mass of molecular gas in galaxies. Translating the molecular gas mass estimates between studies using different lines requires a good ...understanding of the behaviour of the CO(2–1)-to-CO(1–0) ratio, R21. We compare new, high-quality CO(1–0) data from the IRAM 30-m EMIR MultiLine Probe of the ISM Regulating Galaxy Evolution survey to the latest available CO(2–1) maps from HERA CO-Line Extragalactic Survey, Physics at High Angular resolution in Nearby Galaxies-ALMA, and a new IRAM 30-m M51 Large Program. This allows us to measure R21 across the full star-forming disc of nine nearby, massive, star-forming spiral galaxies at 27 arcsec (∼1–2 kpc) resolution. We find an average R21 = 0.64 ± 0.09 when we take the luminosity-weighted mean of all individual galaxies. This result is consistent with the mean ratio for disc galaxies that we derive from single-pointing measurements in the literature, $R_{\rm 21, lit}~=~0.59^{+0.18}_{-0.09}$. The ratio shows weak radial variations compared to the point-to-point scatter in the data. In six out of nine targets, the central enhancement in R21 with respect to the galaxy-wide mean is of order of ${\sim}10{-}20{{\ \rm per\ cent}}$. We estimate an azimuthal scatter of ∼20 per cent in R21 at fixed galactocentric radius but this measurement is limited by our comparatively coarse resolution of 1.5 kpc. We find mild correlations between R21 and carbon monoxide (CO) brightness temperature, infrared (IR) intensity, 70–160 µm ratio, and IR-to-CO ratio. All correlations indicate that R21 increases with gas surface density, star formation rate surface density, and the interstellar radiation field.
Prenatal diagnosis of 46, XX male fetus Trujillo-Tiebas, M J; González-González, C; Lorda-Sánchez, I ...
Journal of assisted reproduction and genetics
23, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Prenatal diagnosis of sex differentiation disorders is extremely rare and is estimated in 1/2500 analyzed gestations. A group of this disorders are the 46, XX males and its incidence is estimated in ...1/20000 male neonates. We report a male XX fetus in which the diagnosis of sex determination was requested at 20 gestation weeks to clarify the real gender of the fetus. Discrepancy between cytogenetic and ultrasonographic was detected.
Abstract Background Excessive myocardial collagen cross-linking (CCL) determines myocardial collagen’s resistance to degradation by matrix metalloproteinase (MMP)-1 and interstitial accumulation of ...collagen fibers with impairment of cardiac function. Objectives This study sought to investigate whether CCL and a newly identified biomarker of this alteration are associated with hospitalization for heart failure (HHF) or cardiovascular death in patients with HF and arterial hypertension in whom other comorbidities were excluded. Methods Endomyocardial biopsies and blood samples from 38 patients (invasive study), and blood samples from 203 patients (noninvasive study) were analyzed. Mean follow-ups were 7.74 ± 0.58 years and 4.72 ± 0.11 years, respectively. Myocardial CCL was calculated as the ratio between insoluble and soluble collagen. The ratio between the C-terminal telopeptide of collagen type I (CITP) and matrix metalloproteinase-1 (CITP:MMP-1) was determined in blood samples. Results Invasive study: CCL was increased (p < 0.001) in patients compared with controls. Patients were categorized according to normal or high CCL values. Patients with high CCL exhibited higher risk for subsequent HHF (log-rank test p = 0.022), but not for cardiovascular death. CITP:MMP-1 was inversely associated with CCL (r = −0.460; p = 0.005) in all patients. Receiver operating characteristic curves rendered a CITP:MMP-1 cutoff ≤1.968 (80% sensitivity and 76% specificity) for predicting high CCL. Noninvasive study: Patients were categorized according to CITP:MMP-1 ratio values as normal ratio (>1.968) or low ratio (≤1.968). Patients with a low ratio exhibited higher risk for HHF (log-rank test p = 0.014), which remained significant after adjustment for relevant covariables (adjusted hazard ratio: 2.22; 95% CI: 1.37 to 3.59, p = 0.001). In addition, CITP:MMP-1–based categorization yielded significant integrated discrimination and net reclassification improvements (p = 0.003 and p = 0.009, respectively) for HHF over relevant risk factors. CITP:MMP-1 was not associated with the risk of cardiovascular death. Conclusions Excessive myocardial CCL is associated with HHF in hypertensive patients with HF. In this population, the serum CITP:MMP-1 ratio identifies patients with increased CCL and high risk of HHF.
Formation of S0 galaxies through mergers Querejeta, M.; Eliche-Moral, M. C.; Tapia, T. ...
Astronomy and astrophysics (Berlin),
01/2015, Letnik:
573
Journal Article
Recenzirano
Odprti dostop
Context. Observations reveal a strong structural coupling between bulge and disc in S0 galaxies, which seems difficult to explain if they have formed from supposedly catastrophic events such as major ...mergers. Aims. We face this question by quantifying the bulge-disc coupling in dissipative simulations of major and minor mergers that result in realistic S0s. Methods. We have studied the dissipative N-body binary merger simulations from the GalMer database that give rise to realistic, relaxed E/S0 and S0 remnants (67 major and 29 minor mergers). We simulate surface brightness profiles of these S0-like remnants in the K band, mimicking typical observational conditions, to perform bulge-disc decompositions analogous to those carried out in real S0s. Additional components have been included when needed. The global bulge-disc structure of these remnants has been compared with real data. Results. The S0-like remnants distribute in the B/T – re – hd parameter space consistently with real bright S0s, where B/T is the bulge-to-total luminosity ratio, re is the bulge effective radius, and hd is the disc scalelength. Major mergers can rebuild a bulge-disc coupling in the remnants after having destroyed the structures of the progenitors, whereas minor mergers directly preserve them. Remnants exhibit B/T and re/hd spanning a wide range of values, and their distribution is consistent with observations. Many remnants have bulge Sérsic indices ranging 1 <n< 2, flat appearance, and contain residual star formation in embedded discs, a result which agrees with the presence of pseudobulges in real S0s. Conclusions. Contrary to the popular view, mergers (and in particular, major events) can result in S0 remnants with realistically coupled bulge-disc structures in less than ~3 Gyr. The bulge-disc coupling and the presence of pseudobulges in real S0s cannot be used as an argument against the possible major-merger origin of these galaxies.
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