- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1026
- Title:
- Lagoon Nebula M8 T tauri accretion rates
- Short Name:
- J/MNRAS/453/1026
- Date:
- 03 Nov 2021
- Publisher:
- CDS
- Description:
- We estimate the accretion rates of 235 Classical T Tauri star (CTTS) candidates in the Lagoon Nebula using ugri H{alpha} photometry from the VST Photometric H{alpha} survey+. Our sample consists of stars displaying H{alpha} excess, the intensity of which is used to derive accretion rates. For a subset of 87 stars, the intensity of the u-band excess is also used to estimate accretion rates. We find the mean variation in accretion rates measured using H{alpha} and u-band intensities to be ~0.17dex, agreeing with previous estimates (0.04-0.4dex) but for a much larger sample. The spatial distribution of CTTS align with the location of protostars and molecular gas suggesting that they retain an imprint of the natal gas fragmentation process. Strong accretors are concentrated spatially, while weak accretors are more distributed. Our results do not support the sequential star-forming processes suggested in the literature.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/V/127A
- Title:
- MASH Catalogues of Planetary Nebulae
- Short Name:
- V/127A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Macquarie/AAO/Strasbourg H{alpha} Planetary Nebula Catalogue (MASH) contains 903 new true, likely and possible Galactic Planetary Nebulae (PNe) discovered from the AAO/UKST H{alpha} survey of the southern Galactic plane. The combination of depth, resolution, uniformity, and areal coverage of the H {alpha}survey has opened up an hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. This catalogue includes also the spectra of the PNe as FITS files (in the "sp" subdirectory), and a gallery of images created as a combination of the H{alpha} and short red images of the survey. The second part, MASH-II (table mash2.dat) consists of over 300 true, likely and possible new Galactic PNe found after re-examination of the entire AAO/UKST H{alpha} survey of the Southern Galactic Plane in digital form. Over 240 of these new candidates were confirmed as bona fide PNe on the basis of spectroscopic observations. The spectra of this supplement will be available in the future.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/51
- Title:
- Mass accretion rates of PMS stars. VI. LH95 in LMC
- Short Name:
- J/ApJ/875/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the accretion properties of low-mass stars in the LH 95 association within the Large Magellanic Cloud. Using noncontemporaneous wideband optical and narrowband H{alpha} photometry obtained with the Hubble Space Telescope, we identify 245 low-mass pre-main-sequence (PMS) candidates showing H{alpha} excess emission above the 4{sigma} level. We derive their physical parameters, including effective temperatures, luminosities, masses (M_*_), ages, accretion luminosities, and mass accretion rates (dM/dt_acc_). We identify two different stellar populations: younger than ~8Myr with median dM/dt_acc_~5.4x10^-8^M_{sun}_/yr (and M_*_~0.15-1.8M_{sun}_) and older than ~8Myr with median dM/dt_acc_~4.8x10^-9^M_{sun}_/yr (and M_*_~0.6-1.2M_{sun}_). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that dM/dt_acc_ in LH 95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation, according to which higher metallicity limits the accretion process in both rate and duration due to higher radiation pressure. The dM/dt_acc_-M_*_ relationship shows different behavior at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on dM/dt_acc_ cannot be treated independently. With the aim to identify reliable correlations between mass, age, and dM/dt_acc_, we used a multivariate linear regression fit between these parameters for our PMS candidates. The comparison between our results and those obtained in other SFRs of our Galaxy and the Magellanic Clouds confirms the importance of the metallicity for the study of the dM/dt_acc_ evolution in clusters with different environmental conditions.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/103
- Title:
- Medium-band photometry RM of 5 nearby AGNs
- Short Name:
- J/ApJ/884/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reverberation mapping (RM) is one of the most efficient ways to investigate the broad-line region around the central supermassive black holes of active galactic nuclei (AGNs). A common way of performing the RM is to perform a long term spectroscopic monitoring of AGNs, but the spectroscopic monitoring campaign of a large number of AGNs requires an extensive amount of observing time of medium to large size telescopes. As an alternative way, we present the results of photometric RM with medium-band photometry. As the widths of medium-band filters match well with the widths of AGN broad emission lines, the medium-band observation with small telescopes can be a cost-effective way to perform RM. We monitored five nearby AGNs with available spectroscopic RM results showing days to weeks scale variability. Observations were performed for ~3 months with an average of 3 days cadence using three medium-band filters on a 0.43m telescope. The time lags between the continuum and the H{alpha} emission line light curves are calculated using the JAVELIN software and the discrete correlation function. We find time lags of 1.5-15.9d for these AGNs, which are consistent with the time lags derived from previous spectroscopic RM measurements. This result demonstrates that even a 0.5m class telescope can perform RM with medium-bands. Furthermore, we show that RM for tens of thousands AGNs is possible with a dedicated 1m class telescope.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/134
- Title:
- M33 SNR candidates properties
- Short Name:
- J/ApJ/793/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Narrowband images covering strong emission lines are efficient for surveying supernova remnants (SNRs) in nearby galaxies. Using the narrowband images provided by the Local Group Galaxy Survey, we searched for SNRs in M33. Culling the objects with enhanced [S II]/H{alpha} and round morphology in the continuum-subtracted H{alpha} and [S II] images, we produced a list of 199 sources. Among them, 79 are previously unknown. Their progenitor and morphology types were classified. A majority of the sample (170 objects) are likely remnants of core-collapse supernovae (SNe), and 29 are remnants of Type Ia SNe. The cumulative size distribution of these objects is found to be similar to that of the M31 remnants derived in a similar way. We obtain a power-law slope, {alpha}=2.38+/-0.05. Thus, a majority of the sources are considered to be in the Sedov-Taylor phase, consistent with previous findings. The histogram of the emission-line ratio ([S II]/H{alpha}) of the remnants has two concentrations at [S II]/H{alpha} ~0.55 and ~0.8, as in M31. Interestingly, L_X_(and L_20 cm_) of the compact center-bright objects are correlated with their optical luminosity. The remnants with X-ray emission have brighter optical surface brightnesses and smaller diameters than those without X-ray emission.
- ID:
- ivo://CDS.VizieR/J/MNRAS/391/1279
- Title:
- Multiwavelength study of NGC 7419
- Short Name:
- J/MNRAS/391/1279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new UBVRI H{alpha} CCD photometric observations and the archival infrared and X-ray data, we have carried out a multiwavelength study of a Perseus arm young open star cluster NGC 7419. Using XMM-Newton observations, we found several X-ray sources in the cluster region but none of the Herbig Ae/Be stars is detected in X-rays.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/81
- Title:
- Multiwavelength survey of HII regions in NGC 300
- Short Name:
- J/ApJ/789/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 H II regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250pc scales using pointed CO(J=2-1) observations with the Atacama Pathfinder Experiment telescope. We detect CO in 42 of our targets, deriving molecular gas masses ranging from our sensitivity limit of ~10^5^M_{sun}_ to 7x10^5^M_{sun}_. We find a clear decline in the CO detection rate with galactocentric distance, which we attribute primarily to the decreasing radial metallicity gradient in NGC 300. We combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24{mu}m, and H{alpha} narrowband imaging to measure the star formation activity in our sample. We have developed a new direct modeling approach for computing star formation rates (SFRs) that utilizes these data and population synthesis models to derive the masses and ages of the young stellar clusters associated with each of our H II region targets. We find a characteristic gas depletion time of 230Myr at 250pc scales in NGC 300, more similar to the results obtained for Milky Way giant molecular clouds than the longer (>2Gyr) global depletion times derived for entire galaxies and kiloparsec-sized regions within them. This difference is partially due to the fact that our study accounts for only the gas and stars within the youngest star-forming regions. We also note a large scatter in the NGC 300 SFR-molecular gas mass scaling relation that is furthermore consistent with the Milky Way cloud results. This scatter likely represents real differences in giant molecular cloud physical properties such as the dense gas fraction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3855
- Title:
- New OB star candidates in Carina Arm
- Short Name:
- J/MNRAS/450/3855
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- O and early B stars are at the apex of galactic ecology, but in the Milky Way, only a minority of them may yet have been identified. We present the results of a pilot study to select and parametrize OB star candidates in the Southern Galactic plane, down to a limiting magnitude of g=20. A 2 deg^2^ field capturing the Carina Arm around the young massive star cluster, Westerlund 2, is examined. The confirmed OB stars in this cluster are used to validate our identification method, based on selection from the (u-g, g-r) diagram for the region. Our Markov Chain Monte Carlo fitting method combines VPHAS+ u, g, r, i with published J, H, K photometry in order to derive posterior probability distributions of the stellar parameters log(Teff) and distance modulus, together with the reddening parameters A_0_ and R_V_. The stellar parameters are sufficient to confirm OB status while the reddening parameters are determined to a precision of {sigma}(A_0_)~0.09 and {sigma}(R_V_)~0.08. There are 489 objects that fit well as new OB candidates, earlier than ~ B2. This total includes 74 probable massive O stars, 5 likely blue supergiants and 32 reddened subdwarfs. This increases the number of previously known and candidate OB stars in the region by nearly a factor of 10. Most of the new objects are likely to be at distances between 3 and 6 kpc. We have confirmed the results of previous studies that, at these longer distances, these sight lines require non-standard reddening laws with 3.5<R_V_<4.
- ID:
- ivo://CDS.VizieR/J/MNRAS/365/401
- Title:
- New planetary nebulae in LMC
- Short Name:
- J/MNRAS/365/401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report our initial discovery of 73 new planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) following confirmatory 2dF spectroscopy on the Anglo-Australian Telescope. Preliminary candidate sources come from a 10 per cent sub-area of our new deep, high-resolution H{alpha} map of the central 25deg^2^ of the LMC obtained with the UK Schmidt Telescope. The depth of the high-resolution map was extended to R_equiv_~22 for H{alpha} (4.5x10^-17^erg/cm^2^/s/{AA}) by a process of multi-exposure median co-addition of a dozen 2-h H{alpha} exposures. The resulting map is at least 1-mag deeper than the best wide-field narrow-band LMC images currently available. This depth, combined with our selection technique, has also led to the discovery of extended asymptotic giant branch (AGB) haloes around many new and previously known LMC PNe for the first time. Once complete, our new survey is expected to triple the LMC PN population and have significant implications for the LMC PN luminosity function, kinematics, abundance gradients, chemical evolution and, via study of the AGB haloes, the initial to final mass relation for low- to intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A45
- Title:
- NGC4330 GHASP and PUMA datacubes
- Short Name:
- J/A+A/659/A45
- Date:
- 04 Mar 2022 00:48:25
- Publisher:
- CDS
- Description:
- Using the VESTIGE survey, a deep narrow-band H{alpha} imaging survey of the Virgo cluster carried on at the CFHT with MegaCam, we have discovered a long and diffuse tail of ionised gas in the edge-on late-type galaxy NGC4330. This peculiar feature witnesses an ongoing ram pressure stripping event able to remove the gas in the outer region of the disc. Tuned hydrodynamic simulations suggest that the ram pressure stripping event is occurring almost face-on, making NGC4330 the ideal candidate to study the effects of the perturbation in the direction perpendicular to the disc plane. We present here two new independent sets of Fabry-Perot observations (R~10000) with the purpose of understanding the effects of ram pressure stripping process on the kinematics of the ionised gas. Despite their limited sensitivity to the diffuse gas emission, the data allowed us to measure the velocity and the velocity dispersion fields over the galaxy disc and in several features at the edges or outside the stellar disc formed after the ram pressure stripping event. We have constructed the position-velocity diagrams and the rotation curves of the galaxy using three different techniques. The data show, consistent with the hydrodynamic simulations, that the galaxy has an inner solid-body rotation up to ~2.4kpc, with noncircular streaming motions outwards the disc and in the several external features formed during the interaction of the galaxy with the surrounding intracluster medium. The data also indicate a decrease of the rotational velocity of the gas with increasing distance from the galaxy disc along the tails, suggesting a gradual but not linear loss of angular momentum in the stripped gas. Consistent with a ram pressure stripping scenario, the i-band image shows a boxy shape at the southwest edge of the disc, where the stellar orbits might have been perturbed by the modification of the gravitational potential well of the galaxy due to the displacement of the gas in the z-direction.
