Mapping the 13CO/C18O abundance ratio in the massive star forming region G29.96-0.02

Estimating molecular abundances ratios from the direct measurement of the emission of the molecules towards a variety of interstellar environments is indeed very useful to advance in our understanding of the chemical evolution of the Galaxy, and hence of the physical processes related to the chemistry. It is necessary to increase the sample of molecular clouds, located at different distances, in which the behavior of molecular abundance ratios, such as the 13CO/C18O ratio (X), is studied in detail. We selected the well-studied high-mass star-forming region G29.96-0.02, located at a distance of about 6.2 kpc, which is an ideal laboratory to perform this kind of studies. To study the X towards this region it was used 12CO J=3-2 data obtained from COHRS, 13CO and C18O J=3-2 data from CHIMPS, and 13CO and C18O J=2-1 data retrieved from the CDS database (observed with the IRAM 30m telescope). The distribution of column densities and X throughout the molecular cloud was studied based on LTE and non-LTE methods. Values of X between 1.5 to 10.5, with an average of 5, were found, showing that, besides the dependency between X and the galactocentric distance, the local physical conditions may strongly affect this abundance ratio. We found that correlating the X map with the location of the ionized gas and dark clouds allows us to suggest in which regions the far-UV radiation stalls in dense gaseous components, and in which ones it escapes and selectively photodissociates the C18O isotope. The non-LTE analysis shows that the molecular gas has very different physical conditions, not only spatially across the cloud, but also along the line of sight. This kind of studies may represent a tool to indirectly estimate (from molecular lines observations) the degree of photodissociation in molecular clouds, which is indeed useful to study the chemistry in the interstellar medium.Comment: Accepted in A&A (July 10, 2018

Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive YSO, was observed in molecular lines with the aim of discover and study molecular outflows. We mapped a region of 3'x3' centered at MSXG34 using the Atacama Submillimeter Telescope Experiment in the 12CO J=3-2 and HCO+ J=4-3 lines with an angular and spectral resolution of 22" and 0.11 km/s, respectively. Additionally, public 13CO J=1-0 and near-IR UKIDSS data obtained from the Galactic Ring Survey and the WFCAM Sciencie Archive, respectively, were analyzed. We found that the 12CO spectra towards the YSO present a self-absorption dip, as it is usual in star forming regions, and spectral wings evidencing outflow activity. The HCO+ was detected only towards the MSXG34 position at v_LSR ~ 14.2 km/s, in coincidence with the 12CO absorption dip and approximately with the velocity of previous ammonia observations. HCO+ and NH3 are known to be enhanced in molecular outflows. Analyzing the spectral wings of the 12CO line, we discovered misaligned red- and blue-shifted molecular outflows associated with MSXG34. The near-IR emission shows a cone-like shape nebulosity composed by two arc-like features related to the YSO, which can be due to a cavity cleared in the circumstellar material by a precessing jet. This can explain the misalignment in the molecular outflows. From the analysis of the 13CO J=1--0 data we suggest that the YSO is very likely related to a molecular clump ranging between 10 and 14 km/s. This suggests that MSXG34, with an associated central velocity of about 14 km/s, may be located in the background of this clump. Thus, the blue-shifted outflow is probably deflected by the interaction with dense gas along the line of sight.Comment: Accepted in A&A June 10, 201

Unveiling the circumstellar environment towards a massive young stellar object

As a continuation of a previous work, in which we found strong evidence of massive molecular outflows towards a massive star forming site, we present a new study of this region based on very high angular resolution observations with the aim of discovering the outflow driven mechanism. Using near-IR data acquired with Gemini-NIRI at the broad H- and Ks-bands, we study a region of 22" x 22" around the UCHII region G045.47+0.05, a massive star forming site at the distance of about 8 kpc. To image the source with the highest spatial resolution possible we employed the adaptative optic system ALTAIR, achieving an angular resolution of about 0.15". We discovered a cone-like shape nebula with an opening angle of about 90 degree extending eastwards the IR source 2MASS J19142564+1109283, a very likely MYSO. This morphology suggests a cavity that was cleared in the circumstellar material and its emission may arise from scattered continuum light, warm dust, and likely emission lines from shock-excited gas. The nebula, presenting arc-like features, is connected with the IR source through a jet-like structure, which is aligned with the blue shifted CO outflow found in a previous study. The near-IR structure lies ~3" north of the radio continuum emission, revealing that it is not spatially coincident with the UCHII region. The observed morphology and structure of the near-IR nebula strongly suggest the presence of a precessing jet. In this study we have resolved the circumstellar ambient (in scale of a thousand A.U.) of a distant MYSO, indeed one of the farthest cases.Comment: Accepted in A&A Letters (October 2013

On LpL^p--LqL^q trace inequalities

We give necessary and sufficient conditions in order that inequalities of the type $$\| T_K f\|_{L^q(d\mu)}\leq C \|f\|_{L^p(d\sigma)}, \qquad f \in L^p(d\sigma),$$ hold for a class of integral operators $T_K f(x) = \int_{R^n} K(x, y) f(y) d \sigma(y)$ with nonnegative kernels, and measures $d \mu$ and $d\sigma$ on $\R^n$, in the case where $p>q>0$ and $p>1$. An important model is provided by the dyadic integral operator with kernel $K_{\mathcal D}(x, y) \sum_{Q\in{\mathcal D}} K(Q) \chi_Q(x) \chi_Q(y)$, where $\mathcal D=\{Q\}$ is the family of all dyadic cubes in $\R^n$, and $K(Q)$ are arbitrary nonnegative constants associated with $Q \in{\mathcal D}$. The corresponding continuous versions are deduced from their dyadic counterparts. In particular, we show that, for the convolution operator $T_k f = k\star f$ with positive radially decreasing kernel $k(|x-y|)$, the trace inequality $$\| T_k f\|_{L^q(d\mu)}\leq C \|f\|_{L^p(d x)}, \qquad f \in L^p(dx),$$ holds if and only if ${\mathcal W}_{k}[\mu] \in L^s (d\mu)$, where $s = {\frac{q(p-1)}{p-q}}$. Here ${\mathcal W}_{k}[\mu]$ is a nonlinear Wolff potential defined by ${\mathcal W}_{k}[\mu](x)=\int_0^{+\infty} k(r) \bar{k}(r)^{\frac 1 {p-1}} \mu (B(x,r))^{\frac 1{p-1}} r^{n-1} dr,$ and $\bar{k}(r)=\frac1{r^n}\int_0^r k(t) t^{n-1} dt$. Analogous inequalities for $1\le q < p$ were characterized earlier by the authors using a different method which is not applicable when $q<1$

Studying the Molecular Ambient towards the Young Stellar Object EGO G35.04-0.47

We are performing a systematic study of the interstellar medium around extended green objects (EGOs), likely massive young stellar objects driving outflows. EGO G35.04-0.47 is located towards a dark cloud at the northern-west edge of an HII region. Recently, H2 jets were discovered towards this source, mainly towards its southwest, where the H2 1-0 S(1) emission peaks. Therefore, the source was catalogued as the Molecular Hydrogen emission-line object MHO 2429. In order to study the molecular ambient towards this star-forming site, we observed a region around the aforementioned EGO using the Atacama Submillimeter Telescope Experiment in the 12CO J=3--2, 13CO J=3--2, HCO+ J=4--3, and CS J=7--6 lines with an angular and spectral resolution of 22" and 0.11 km s-1, respectively. The observations revealed a molecular clump where the EGO is embedded at v_LSR ~ 51 km s-1, in coincidence with the velocity of a Class I 95 GHz methanol maser previously detected. Analyzing the 12CO line we discovered high velocity molecular gas in the range from 34 to 47 km s-1, most likely a blueshifted outflow driven by the EGO. The alignment and shape of this molecular structure coincide with those of the southwest lobe of MHO 2429 mainly between 46 and 47 km s-1, confirming that we are mapping its CO counterpart. Performing a SED analysis of EGO G35.04-0.47 we found that its central object should be an intermediate-mass young stellar object accreting mass at a rate similar to those found in some massive YSOs. We suggest that this source can become a massive YSO.Comment: accepted to be published in PASJ - 24 September 201

12CO and 13CO J=3-2 observations toward N11 in the Large Magellanic Cloud

After 30 Doradus, N11 is the second largest and brightest nebula in the LMC. This large nebula has several OB associations with bright nebulae at its surroundings. N11 was previously mapped at the lowest rotational transitions of $^{12}$CO (J=1--0 and 2--1), and in some particular regions pointings of the $^{13}$CO J=1--0 and 2--1 lines were also performed. Using ASTE we mapped the whole extension of the N11 nebula in the $^{12}$CO J=3--2 line, and three sub-regions in the $^{13}$CO J=3--2 line. The regions mapped in the $^{13}$CO J=3--2 were selected based on that they may be exposed to the radiation at different ways: a region lying over the nebula related to the OB association LH10 (N11B), another one that it is associated with the southern part of the nebula related to the OB association LH13 (N11D), and finally a farther area at the southwest without any embedded OB association (N11I). We found that the morphology of the molecular clouds lying in each region shows some signatures that could be explained by the expansion of the nebulae and the action of the radiation. Fragmentation generated in a molecular shell due to the expansion of the N11 nebula is suggested. The integrated line ratios $^{12}$CO/$^{13}$CO show evidences of selective photodissociation of the $^{13}$CO, and probably other mechanisms such as chemical fractionation. The CO contribution to the continuum at 870 $\mu$m was directly derived. The distribution of the integrated line ratios $^{12}$CO J=3--2/2--1 show hints of stellar feedback in N11B and N11D. The ratio between the virial and LTE mass (M$_{\rm vir}$/M$_{\rm LTE}$) is higher than unity in all analyzed molecular clumps, which suggests that the clumps are not gravitationally bounded and may be supported by external pressure. A non-LTE analysis suggests that we are mapping gas with densities about a few 10$^{3}$ cm$^{-3}$.Comment: Accepted to be published in A&A. Figures were degrade