Search

Start Over Subject spectroscopy Content Level Research
2191. RGB stars in LMC outer disk
ID:
ivo://CDS.VizieR/J/AJ/142/61
Title:
RGB stars in LMC outer disk
Short Name:
J/AJ/142/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
The outer disk of the Large Magellanic Cloud (LMC) is studied in order to unveil clues about its formation and evolution. Complementing our previous studies in innermost fields (3kpc<~R<~7kpc), we obtained deep color-magnitude diagrams in six fields with galactocentric distances from 5.2kpc to 9.2kpc and different azimuths. The comparison with isochrones shows that while the oldest population is approximately coeval in all fields, the age of the youngest populations increases with increasing radius. This agrees with the results obtained in the innermost fields. Low-resolution spectroscopy in the infrared CaII triplet region has been obtained for about 150 stars near the tip of the red giant branch in the same fields. Radial velocities and stellar metallicities have been obtained from these spectra. The metallicity distribution of each field has been analyzed together with those previously studied.
2192. RM AGNs accretion rates and BH masses
ID:
ivo://CDS.VizieR/J/ApJ/818/L14
Title:
RM AGNs accretion rates and BH masses
Short Name:
J/ApJ/818/L14
Date:
21 Oct 2021
Publisher:
CDS
Description:
Broad emission lines in active galactic nuclei (AGNs) mainly arise from gas photoionized by continuum radiation from an accretion disk around a central black hole. The shape of the broad-line profile, described by D_H{beta}_=FWHM/{sigma}_H{beta}_, the ratio of full width at half maximum to the dispersion of broad H{beta}, reflects the dynamics of the broad-line region (BLR) and correlates with the dimensionless accretion rate (dM/dt) or Eddington ratio (L_bot_/L_Edd_). At the same time, dM/dt and (L_bot_/L_Edd_ correlate with R_Fe_, the ratio of optical Fe ii to H{beta} line flux emission. Assembling all AGNs with reverberation mapping measurements of broad H{beta}, both from the literature and from new observations reported here, we find a strong bivariate correlation of the form log((dM/dt.L_bot_/L_Edd_)={alpha}+{beta}D_H{beta}_+{gamma}R_Fe_ where {alpha}=(2.47,0.31), {beta}=-(1.59,0.82), and {gamma}=(1.34,0.80). We refer to this as the fundamental plane of the BLR. We apply the plane to a sample of z<0.8 quasars to demonstrate the prevalence of super-Eddington accreting AGNs are quite common at low redshifts.
2193. RMS survey: molecular observations
ID:
ivo://CDS.VizieR/J/MNRAS/437/1791
Title:
RMS survey: molecular observations
Short Name:
J/MNRAS/437/1791
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the well-selected sample of ~1750 embedded, young, massive stars identified by the Red MSX Source (RMS) survey to investigate the Galactic distribution of recent massive star formation. We present molecular line observations for ~800 sources without existing radial velocities. We describe the various methods used to assign distances extracted from the literature and solve the distance ambiguities towards approximately 200 sources located within the solar circle using archival Hi data. These distances are used to calculate bolometric luminosities and estimate the survey completeness (~2x10^4^L_{sun}_). In total, we calculate the distance and luminosity of ~1650 sources, one third of which are above the survey's completeness threshold. Examination of the sample's longitude, latitude, radial velocities and mid-infrared images has identified ~120 small groups of sources, many of which are associated with well-known star formation complexes, such as G305, G333, W31, W43, W49 and W51. We compare the positional distribution of the sample with the expected locations of the spiral arms, assuming a model of the Galaxy consisting of four gaseous arms. The distribution of young massive stars in the Milky Way is spatially correlated with the spiral arms, with strong peaks in the source position and luminosity distributions at the arms' Galactocentric radii. The overall source and luminosity surface densities are both well correlated with the surface density of the molecular gas, which suggests that the massive star formation rate per unit molecular mass is approximately constant across the Galaxy. A comparison of the distribution of molecular gas and the young massive stars to that in other nearby spiral galaxies shows similar radial dependences. We estimate the total luminosity of the embedded massive star population to be ~0.76x10^8^L_{sun}_, 30 per cent of which is associated with the 10 most active star-forming complexes. We measure the scaleheight as a function of the Galactocentric distance and find that it increases only modestly from ~20-30pc between 4 and 8kpc, but much more rapidly at larger distances.
2194. RMS survey: NIR spectroscopy of massive YSOs
ID:
ivo://CDS.VizieR/J/MNRAS/430/1125
Title:
RMS survey: NIR spectroscopy of massive YSOs
Short Name:
J/MNRAS/430/1125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (~80%) of the targets are YSOs, of which 131 are massive YSOs (L_BOL_>5x10^3^L_{sun}_, M>8M_{sun}_). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7<A_V_<114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Br{gamma}, H_2_, fluorescent FeII, CO bandhead, [FeII] and HeI 2-1 1S-1P, in order of frequency of occurrence. In total, ~40% of the YSOs display either fluorescent FeII 1.6878{mu}m or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ~60% of the sources exhibit [FeII] or H_2_ emission, indicating the presence of an outflow. Three quarters of all sources have Br{gamma} in emission. A good correlation with bolometric luminosity was observed for both the Br{gamma} and H_2_ emission line strengths, covering 1<L_BOL_<3.5x10^5^L_{sun}_. This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs.
2195. ROGUE. I. SDSS galaxies with FIRST
ID:
ivo://CDS.VizieR/J/ApJS/247/53
Title:
ROGUE. I. SDSS galaxies with FIRST
Short Name:
J/ApJS/247/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the catalog of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE I), consisting of 32616 spectroscopically selected galaxies. It is the largest handmade catalog of this kind, obtained by cross-matching galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 and radio sources from both the First Images of Radio Sky at Twenty Centimetre (FIRST) survey and the NRAO Very Large Array Sky Survey, without imposing a limit on the radio flux densities. The catalog provides a visual classification of radio and optical morphologies of galaxies presenting a FIRST core within 3" of the optical position. The radio morphological classification is performed by examining the radio-optical overlays of linear sizes equal to 1Mpc at the source distance, while the 120" image snapshots from the SDSS database are used for optical classification. The results of our search are as follows: (i) single-component unresolved and elongated radio sources constitute the major group in the ROGUE I catalog (~90%), and ~8% exhibit extended morphologies; (ii) samples of 269, 730, and 115 Fanaroff-Riley (FR) type I, II, and hybrid galaxies, respectively, are presented; (iii) we report 55 newly discovered giant/possible giant, 16 double-double, 9 X-shaped, and 25 Z-shaped radio sources; (iv) on the optical front, most galaxies have elliptical morphologies (~62%) while spirals form the second major category (~17%) followed by distorted (~12%) and lenticular (~7%) morphologies; and (v) division between the FR I and the FR II sources in the radio-optical luminosity plane is blurred, in tune with recent studies.
2196. Role of starburst-AGN composites in LIRG mergers
ID:
ivo://CDS.VizieR/J/ApJ/709/884
Title:
Role of starburst-AGN composites in LIRG mergers
Short Name:
J/ApJ/709/884
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the fraction of starbursts, starburst-active galactic nucleus (AGN) composites, Seyferts, and low-ionization narrow emission-line region galaxies (LINERs) as a function of infrared luminosity (LIR) and merger progress for ~500 infrared (IR)-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare (<5%) compared with other spectral types. The lack of strong IR emission in LINERs is consistent with recent optical studies suggesting that LINERs contain AGN with lower accretion rates than in Seyfert galaxies. Most previously classified IR-luminous LINERs are classified as starburst-AGN composite galaxies in the new scheme. Starburst-AGN composites appear to "bridge" the spectral evolution from starburst to AGN in ULIRGs. The relative strength of the AGN versus starburst activity shows a significant increase at high IR luminosity. In ULIRGs (LIR>10^12^L_{sun}_), starburst-AGN composite galaxies dominate at early-intermediate stages of the merger, and AGN galaxies dominate during the final merger stages.
2197. Rotation-Activity Correlations in K-M dwarfs II.
ID:
ivo://CDS.VizieR/J/ApJ/837/96
Title:
Rotation-Activity Correlations in K-M dwarfs II.
Short Name:
J/ApJ/837/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the rotation-activity correlations (RACs) in a sample of stars from spectral type dK4 to dM4. We study RACs using chromospheric data and coronal data. We study the Ca II line surface fluxes-P/sini RACs. We fit the RACs with linear homoscedastic and heteroscedastic regression models. We find that these RACs differ substantially from one spectral sub-type to another. For dM3 and dM4 stars, we find that the RACs cannot be described by a simple model, but instead that there may exist two distinct RAC behaviors for the low-activity and the high-activity stellar sub-samples, respectively. Although these results are preliminary and will need confirmation, the data suggest that these distinct RACs may be associated with different dynamo regimes. We also study R'_HK_ as a function of the Rossby number R_0_. We find (i) for dK4 stars, R'_HK_ as a function of R_0_ agrees well with previous results for F-G-K stars and (ii) in dK6, dM2, dM3, and dM4 stars, at a given R_0_, the values of R'_HK_ lie at a factor of 3, 10, 20, and 90, respectively, below the F-G-K RAC. Our results suggest a significant decrease in the efficiency of the dynamo mechanism(s) as regards chromospheric heating before and at dM3, i.e., before and at the transition to complete convection. We also show that the ratio of coronal heating to chromospheric heating L_X_/L_HK_ increases by a factor of 100 between dK4 and dM4 stars.
2198. Rotational spectroscopy of CH_2_OH
ID:
ivo://CDS.VizieR/J/A+A/644/A123
Title:
Rotational spectroscopy of CH_2_OH
Short Name:
J/A+A/644/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
The hydroxymethyl radical (CH_2_OH) is one of the two structural isomers, together with the methoxy radical (CH_3_O), that can be produced by abstraction of a hydrogen atom from methanol (CH_3_OH). In the interstellar medium (ISM), both CH_2_OH and CH_3_O are suspected to be intermediate species in many chemical reactions, including those of formation and destruction of methanol. The determination of the CH_3_O/CH_2_OH ratio in the ISM would bring important information concerning the formation processes of these species in the gas and solid phases. Interestingly, only CH_3_O has been detected in the ISM so far, despite the recent first laboratory measurement of the CH_2_OH rotation-tunneling spectrum. This lack of detection is possibly due to the non-observation in the laboratory of the most intense rotational-tunneling transitions at low temperature. To support further searches for the hydroxymethyl radical in space, we have performed a thorough spectroscopic study of its rotation-tunneling spectrum, with particular focus on transitions involving the lowest quantum numbers of the species. We have recorded the rotation-tunneling spectrum of CH_2_OH at room temperature in the millimeter-wave domain using a frequency multiplication chain spectrometer associated to a fluorine-induced H-abstraction method. The radical was produced from methanol precursor. About 180 transitions were observed including those involving the lowest N and Ka quantum numbers, predicted intense under cold astrophysical conditions. These transitions were fitted together with available millimeter-wave lines from the literature. The systematic observation of all components of the rotational transitions yields a large improvement of the spectroscopic parameters which now allow confident searches of the hydroxymethyl radical in cold to warm environments of the ISM.
2199. Rotational spectrum and DCOOCH_3_ in Orion
ID:
ivo://CDS.VizieR/J/ApJ/714/1120
Title:
Rotational spectrum and DCOOCH_3_ in Orion
Short Name:
J/ApJ/714/1120
Date:
21 Oct 2021
Publisher:
CDS
Description:
New centimeter-wave (7-80GHz) and submillimeter-wave (580-661GHz) spectra of a deuterated species of methyl formate (DCOOCH_3_) have been measured. Transitions with a maximum value of J=64 and K=36 have been assigned and fitted together with previous measurements. The internal rotation of this compound was treated using the so-called rho axis method (RAM). A total of 1703 transitions were fitted using this method. Only 24 parameters were employed in the final fit, which has an rms deviation of 94.2kHz. The dipole moment and the nuclear quadrupole coupling constants of the deuterated species have also been obtained. This new study has permitted a tentative detection of DCOOCH_3_ in Orion with the IRAM 30m telescope based on the observation of more than 100 spectral features with low blending effects among the 400 lines expected in the observed frequency domain (for which over 300 are heavily blended with other species). These 100 transitions are above noise and confusion limited without heavy blending and cannot be assigned to any other species. Moreover, none of the strongest unblended transitions is missing. The derived source-averaged total column density for DCOOCH_3_ is 7.8x10^14^cm^-2^ and the DCOOCH_3_/HCOOCH_3_ column density ratio varies between 0.02 and 0.06 in the different cloud components of Orion. This value is consistent with the deuteration enhancement found for other species in this cloud.
2200. Rotational spectrum of CH_3_CH(NH_2_)CN
ID:
ivo://CDS.VizieR/J/A+A/538/A51
Title:
Rotational spectrum of CH_3_CH(NH_2_)CN
Short Name:
J/A+A/538/A51
Date:
21 Oct 2021
Publisher:
CDS
Description:
No chiral molecule has been detected in the interstellar medium (ISM) so far. A good candidate for an interstellar detection is 2-aminopropionitrile (CH_3_CH(NH_2_)CN), a chiral and the simplest molecule with a C_3_H_6_N_2_ formula. The first member of this series, aminoacetonitrile (H_2_NCH_2_CN), was recently detected, demonstrating that at least one aminonitrile exist in the ISM. Experimental spectra of 2-aminopropionitrile have been recorded in the microwave and sub-mm energy range (8-80GHz, 150-660GHz). An unbiased spectral survey of the 80-116GHz atmospheric window performed with the IRAM 30m telescope is used to search for this molecule in the hot core Sgr B2(N). This survey is analysed in the local thermodynamical equilibrium (LTE) approximation. The emission of 2-aminopropionitrile is modeled simultaneously with the emission of all molecules known in Sgr B2(N), which allows to properly take into account line blending and avoid mis-assignments. Only 10 groups of transitions of 2-aminopropionitrile are not severely affected by line blending in the Sgr B2(N) spectrum. Six of them could be considered as tentatively detected but the LTE predictions of the four remaining groups are not (or only marginally) consistent with the observed spectrum. Therefore, only an upper limit of 1.7*10^16^cm^-2^ can be securely derived for the column density of 2-aminopropionitrile toward Sgr B2(N).

Limit your search

more »

more »

more »

more »