- ID:
- ivo://CDS.VizieR/J/MNRAS/439/3719
- Title:
- Embedded clusters infrared photometry
- Short Name:
- J/MNRAS/439/3719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer, near-IR (NIR) and millimetre observations of the massive star-forming regions W5-east, S235, S252, S254-S258 and NGC 7538. Spitzer data is combined with NIR observations to identify and classify the young population while ^12^CO and ^13^CO observations are used to examine the parental molecular cloud. We detect in total 3021 young stellar objects (YSOs). Of those, 539 are classified as Class I, and 1186 as Class II sources. YSOs are distributed in groups surrounded by a more scattered population. Class I sources are more hierarchically organized than Class II and associated with the most dense molecular material. We identify in total 41 embedded clusters containing between 52 and 73 per cent of the YSOs. Clusters are in general non-virialized, turbulent and have star formation efficiencies between 5 and 50 per cent. We compare the physical properties of embedded clusters harbouring massive stars (MEC) and low-mass embedded clusters (LEC) and find that both groups follow similar correlations where the MEC are an extrapolation of the LEC. The mean separation between MEC members is smaller compared to the cluster Jeans length than for LEC members. These results are in agreement with a scenario where stars are formed in hierarchically distributed dusty filaments where fragmentation is mainly driven by turbulence for the more massive clusters. We find several young OB-type stars having IR-excess emission which may be due to the presence of an accretion disc.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/620/A30
- Title:
- 12 embedded protostellar systems APEX spectra
- Short Name:
- J/A+A/620/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure. We aim to study the relationship between envelope gas temperature and protostellar multiplicity. Single dish observations of various molecules that trace the cold, warm and UV-irradiated gas are used to probe the temperature structure of multiple and single protostellar systems on 7000 AU scales. Single, close binary, and wide multiples present similar current envelope gas temperatures, as estimated from H_2_CO and DCO^+^ line ratios. The temperature of the outflow cavity, traced by c-C_3_H_2_, on the other hand, shows a relation with bolometric luminosity and an anticorrelation with envelope mass. Although the envelope gas temperatures are similar for all objects surveyed, wide multiples tend to exhibit a more massive reservoir of cold gas compared to close binary and single protostars. Although the sample of protostellar systems is small, the results suggest that gas temperature may not have a strong impact on fragmentation. We propose that mass, and density, may instead be key factors in fragmentation.
- ID:
- ivo://CDS.VizieR/J/A+A/498/167
- Title:
- Embedded sources in L 1688
- Short Name:
- J/A+A/498/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ophiuchus clouds, in particular L 1688, are an excellent region to study the embedded phases of star formation, due to the relatively large number of protostars. However, the standard method of finding and characterizing embedded young stellar objects (YSOs) through just their infrared spectral slope does not yield a reliable sample. This may affect the age determinations, often derived from the statistics on the total number of embedded YSOs and pre-main sequence stars within a cloud. Our aim is to characterize the structure of protostellar envelopes on an individual basis and to correctly identify the embedded YSO population of L 1688.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/83
- Title:
- Embedded YSO candidates in W51
- Short Name:
- J/ApJ/706/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 737 candidate young stellar objects (YSOs) near the W51 giant molecular cloud over an area of 1.25x1.00{deg} selected from Spitzer Space Telescope data. We use spectral energy distribution fits to identify YSOs and distinguish them from main-sequence (MS) or red giant stars, asymptotic giant branch stars, and background galaxies. Based on extinction of each YSO, we separate a total of 437 YSOs associated with the W51 region from the possible foreground sources. We identify 69 highly embedded Stage 0/I candidate YSOs in our field with masses >5M_{sun}_ (corresponding to mid- to early-B MS spectral types), 46 of which are located in the central active star-forming regions of W51A and W51B. From the YSOs associated with W51, we find evidence for mass segregation showing that the most massive YSOs are concentrated on the W51 HII region complex.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A67
- Title:
- Embedded YSOs in Carina Nebula complex
- Short Name:
- J/A+A/549/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy. It contains numerous very massive (M>~40M_{sun}) stars that strongly act the surrounding clouds by their ionizing radiation and stellar winds. Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (~~8.7{deg}^2^) of the Carina Nebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visible in the mid- or near-infrared. We study the properties of the 642 objects that are independently detected as point-like sources in at least two of the five Herschel bands. For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/460/884
- Title:
- EMBLA survey. Galactic bulge metal-poor stars
- Short Name:
- J/MNRAS/460/884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmological models predict the oldest stars in the Galaxy should be found closest to the centre of the potential well, in the bulge. The Extremely Metal-poor BuLge stars with AAOmega survey (EMBLA) successfully searched for these old, metal-poor stars by making use of the distinctive SkyMapper photometric filters to discover candidate metal-poor stars in the bulge. Their metal-poor nature was then confirmed using the AAOmega spectrograph on the Anglo-Australian Telescope. Here we present an abundance analysis of 10 bulge stars with -2.8<[Fe/H]<-1.7 from MIKE/Magellan observations, in total determining the abundances of 22 elements. Combining these results with our previous high-resolution data taken as part of the Gaia-ESO Survey, we have started to put together a picture of the chemical and kinematic nature of the most metal-poor stars in the bulge. The currently available kinematic data are consistent with the stars belonging to the bulge, although more accurate measurements are needed to constrain the stars' orbits. The chemistry of these bulge stars deviates from that found in halo stars of the same metallicity. Two notable differences are the absence of carbon-enhanced metal-poor bulge stars, and the {alpha} element abundances exhibit a large intrinsic scatter and include stars which are underabundant in these typically enhanced elements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/210
- Title:
- eMERGE Survey. I. VLA 5.5GHz sources
- Short Name:
- J/MNRAS/471/210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new observations of the GOODS-N field obtained at 5.5GHz with the Karl G. Jansky Very Large Array. The central region of the field was imaged to a median rms of 3{mu}Jy/beam with a resolution of 0.5 arcsec. From a 14-arcmin diameter region, we extracted a sample of 94 radio sources with signal-to-noise ratio greater than 5. Near-IR identifications are available for about ~88 per cent of the radio sources. We used different multiband diagnostics to separate active galactic nuclei (AGNs), both radiatively efficient and inefficient, from star-forming galaxies. From our analysis, we find that about 80 per cent of our radio-selected sample is AGN dominated, with the fraction rising to 92 per cent when considering only the radio sources with redshift >1.5. This large fraction of AGN-dominated radio sources at very low flux densities (the median flux density at 5.5GHz is 42{mu}Jy), where star-forming galaxies are expected to dominate, is somewhat surprising and at odds with other results. Our interpretation is that both the frequency and angular resolution of our radio observations strongly select against radio sources whose brightness distribution is diffuse on a scale of several kpc. Indeed, we find that the median angular sizes of the AGN-dominated sources is around 0.2-0.3arcsec against 0.8 arcsec for star-forming galaxies. This highlights the key role that high frequency radio observations can play in pinpointing AGN-driven radio emission at {mu}Jy levels. This work is part of the eMERGE legacy project.
- ID:
- ivo://CDS.VizieR/J/MNRAS/365/454
- Title:
- Emission line analysis of HII galaxies
- Short Name:
- J/MNRAS/365/454
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical study of a very large sample of HII galaxies taken from the literature. We focus on the differences in several properties between galaxies that show the auroral line [OIII]{lambda}4363 and those that do not present this feature in their spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A30
- Title:
- Emission line flux densities for 12 YSOs
- Short Name:
- J/A+A/631/A30
- Date:
- 28 Oct 2021 07:35:47
- Publisher:
- CDS
- Description:
- Episodic accretion plays an important role in the evolution of young stars. Although it has been under investigation for a long time, the origin of such episodic accretion events is not yet understood. We investigate the dust and gas emission of a sample of young outbursting sources in the infrared to get a better understanding of their properties and circumstellar material, and we use the results in a further work to model the objects. We used Herschel data, from our PI program of 12 objects and complemented with archival observations to obtain the spectral energy distributions (SEDs) and spectra of our targets. We report here the main characteristics of our sample, focussing on the SED properties and on the gas emission lines detected in the PACS and SPIRE spectra. The SEDs of our sample show the diversity of the outbursting sources, with several targets showing strong emission in the far-infrared from the embedded objects. Most of our targets reside in a complex environment, which we discuss in detail. We detected several atomic and molecular lines, in particular rotational CO emission from several transitions from J=38-37 to J=4-3. We constructed rotational diagrams for the CO lines, and derived in three domains of assumed local thermodynamic equilibrium (LTE) temperatures and column densities, ranging mainly between 0-100K and 400-500K. We confirm correlation in our sample between intense CO J=16-15 emission and the column density of the warm domain of CO, N(warm). We notice a strong increase in luminosity of HH 381 IRS and a weaker increase for PP 13 S, which shows the beginning of an outburst.
- ID:
- ivo://CDS.VizieR/J/ApJS/192/5
- Title:
- Emission-line galaxies from HETDEX pilot survey
- Short Name:
- J/ApJS/192/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of emission-line galaxies selected solely by their emission-line fluxes using a wide-field integral field spectrograph. This work is partially motivated as a pilot survey for the upcoming Hobby-Eberly Telescope Dark Energy Experiment. We describe the observations, reductions, detections, redshift classifications, line fluxes, and counterpart information for 397 emission-line galaxies detected over 169arcmin^2^ with a 3500-5800{AA} bandpass under 5{AA} full-width-half-maximum (FWHM) spectral resolution. The survey's best sensitivity for unresolved objects under photometric conditions is between 4 and 20x10^-17^erg/s/cm^2^ depending on the wavelength, and Ly{alpha} luminosities between 3x10^42^ and 6x10^42^erg/s are detectable. This survey method complements narrowband and color-selection techniques in the search of high-redshift galaxies with its different selection properties and large volume probed. The four survey fields within the COSMOS, GOODS-N, MUNICS, and XMM-LSS areas are rich with existing, complementary data. We find 105 galaxies via their high-redshift Ly{alpha} emission at 1.9<z<3.8, and the majority of the remainder objects are low-redshift [OII]3727 emitters at z<0.56. The classification between low- and high-redshift objects depends on rest-frame equivalent width (EW), as well as other indicators, where available. Based on matches to X-ray catalogs, the active galactic nuclei fraction among the Ly{alpha} emitters is 6%. We also analyze the survey's completeness and contamination properties through simulations. We find five high-z, highly significant, resolved objects with FWHM sizes >44arcmin^2^ which appear to be extended Ly{alpha} nebulae. We also find three high-z objects with rest-frame Ly{alpha} EW above the level believed to be achievable with normal star formation, EW0>240{AA}.