- ID:
- ivo://CDS.VizieR/J/A+A/658/A4
- Title:
- LOFAR imaging of Arp299 at 150MHz
- Short Name:
- J/A+A/658/A4
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the spatially resolved emission of Arp 299 revealed by 150 MHz international baseline Low-Frequency Array (LOFAR) and 1.4, 5.0, and 8.4GHz Very Large Array (VLA) observations. Nowadays, LOFAR allows to compare its resolution with the VLA ones. These will allow us to obtain pixel-by-pixel spectral imdex maps and local radio SEDs. With this information we recover the nature of the ISM around the main structures (either clumpy or continuous), as well as magnetic fields. The 150MHz image also shows structures never seen before, pointing out that these radio-frequencies observations are a perfect tool to detect them.
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- ID:
- ivo://CDS.VizieR/J/ApJS/179/249
- Title:
- Low-luminosity embedded protostar population
- Short Name:
- J/ApJS/179/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for all embedded protostars with internal luminosities <=1.0L_{sun}_ in the full sample of nearby, low-mass star-forming regions surveyed by the Spitzer Space Telescope Legacy Project "From Molecular Cores to Planet Forming Disks" (c2d). We present a set of selection criteria used to identify candidates from the Spitzer data and examine complementary data to decide whether each candidate is truly an embedded protostar. Between 75% and 85% of cores classified as starless prior to being observed by Spitzer remain starless to our luminosity sensitivity; the remaining 15%-25% harbor low-luminosity, embedded protostars. We compile complete spectral energy distributions for all 50 objects and calculate standard evolutionary signatures (L_bol_, T_bol_, and L_bol_/L_smm_) and argue that these objects are inconsistent with the simplest picture of star formation, wherein mass accretes from the core onto the protostar at a constant rate.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A111
- Title:
- Low-mass stars in Coma Ber
- Short Name:
- J/A+A/544/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Little is known about the population of the Coma Berenices open cluster (age~500Myr) below 0.2M_{sun}_, and statistics show that there is a prominent deficit of very low-mass objects in this mass range compared to younger open clusters with ages of <250Myr. We search for very low-mass stars and substellar objects (brown dwarfs) in the Coma open cluster to derive the present-day cluster mass function below 0.2M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/604/521
- Title:
- Luminosities and masses of galaxies out to z~3
- Short Name:
- J/ApJ/604/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity-size and mass-size distributions of galaxies out to z~3 are presented. We use very deep near-infrared images of the Hubble Deep Field-South in the J_s_, H, and K_s_ bands, taken as part of FIRES at the VLT, to follow the evolution of the optical rest-frame sizes of galaxies. For a total of 168 galaxies with K_s,AB_ <=23.5, we find that the rest-frame V-band sizes r_e,V_ of luminous galaxies (<L_V_>~2x10^10^h^-2^L_{sun}_) at 2<z<3 are 3 times smaller than for equally luminous galaxies today. In contrast, the mass-size relation has evolved relatively little: the size at mass <M_*_>~2x10^10^h^-2^M_{sun}_ has changed by 20% (+/-20%) since z~2.5. Both results can be reconciled by the fact that the stellar M/L ratio is lower in the luminous high-z galaxies than in nearby ones because they have young stellar populations. The lower incidence of large galaxies at z~3 seems to reflect the rarity of galaxies with high stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/145/94
- Title:
- Luminosities of protostars from two Spitzer surveys
- Short Name:
- J/AJ/145/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate L_bol_ for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01L_{sun}_ to 69L_{sun}_, and has a mean and median of 4.3L_{sun}_ and 1.3L_{sun}_, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (L_bol_<~0.5L_{sun}_) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70{mu}m<{lambda}<850{mu}m) and have L_bol_ underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35%-40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased data set should aid such future work.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/45
- Title:
- Luminosity and redshift of galaxies from WISE/SDSS
- Short Name:
- J/ApJ/788/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 {mu}m luminosity functions (LFs) at 0.006<=z<=0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog (Cat. II/311) with Sloan Digital Sky Survey (SDSS, Cat. II/294) spectroscopic data, we selected 223982 galaxies at 12 {mu}m and 25721 galaxies at 22 {mu}m for spectroscopic classification. We then identified 16355 AGNs at 12 {mu}m and 4683 AGNs at 22 {mu}m by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z<=0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A130
- Title:
- Luminous infrared galaxies AKARI 2.5-5um data
- Short Name:
- J/A+A/617/A130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present AKARI 2.5-5um spectra of 145 local luminous infrared galaxies (LIRG; L_IR_>=10^11^L_{sun}_) in the Great Observatories All-sky LIRG Survey (GOALS). In all of the spectra, we measure the line fluxes and equivalent widths (EQWs) of the polycyclic aromatic hydrocarbon (PAH) at 3.3um and the hydrogen recombination line Br{alpha} at 4.05um, with apertures matched to the slit sizes of the Spitzer low-resolution spectrograph and with an aperture covering ~95% of the total flux in the AKARI two-dimensional (2D) spectra. The star formation rates (SFRs) derived from the Br{alpha} emission measured in the latter aperture agree well with SFRs estimated from LIR, when the dust extinction correction is adopted based on the 9.7um silicate absorption feature. Together with the Spitzer Infrared Spectrograph (IRS) 5.2-38um spectra, we are able to compare the emission of the PAH features detected at 3.3um and 6.2um. These are the two most commonly used near/mid-infrared indicators of starburst or active galactic nucleus (AGN) dominated galaxies. We find that the 3.3um and 6.2um PAH EQWs do not follow a linear correlation and at least a third of the galaxies classified as AGN-dominated sources using the 3.3um feature are classified as starbursts based on the 6.2um feature. These galaxies have a bluer continuum slope than galaxies that are indicated to be starburst-dominated by both PAH features. The bluer continuum emission suggests that their continuum is dominated by stellar emission rather than hot dust. We also find that the median Spitzer/IRS spectra of these sources are remarkably similar to the pure starburst-dominated sources indicated by high PAH EQWs in both 3.3um and 6.2um. Based on these results, we propose a revised starburst/AGN diagnostic diagram using 2-5um data: the 3.3um PAH EQW and the continuum color, F{nu}(4.3um)/F{nu}(2.8um). We use the AKARI and Spitzer spectra to examine the performance of our new starburst/AGN diagnostics and to estimate 3.3um PAH fluxes using the James Webb Space Telescope (JWST) photometric bands in the redshift range 0<z<5. Of the known PAH features and mid-infrared high ionization emission lines used as starburst/AGN indicators, only the 3.3um PAH feature is observable with JWST at z>3.5, because the rest of the features at longer wavelengths fall outside the JWST wavelength coverage.
- ID:
- ivo://CDS.VizieR/J/ApJS/154/155
- Title:
- Luminous X-ray sources Chandra fluxes
- Short Name:
- J/ApJS/154/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the luminous X-ray sources in the Lockman Hole (LH) and the extended Groth strip (EGS) detected at 24{mu}m using the Multiband Imaging Photometer (MIPS) and also with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. We assemble optical/infrared spectral energy distributions (SEDs) for 45 X-ray/24{mu}m sources in the EGS and LH. Only about one-quarter of the hard X-ray/24{mu}m sources show pure type 1 active galactic nucleus (AGN) SEDs. More than half of the X-ray/24{mu}m sources have stellar emission-dominated or obscured SEDs, similar to those of local type 2 AGN and spiral/starburst galaxies. One-third of the sources detected in hard X-rays do not have a 24{mu}m counterpart. Two such sources in the LH have SEDs resembling those of S0/elliptical galaxies. The broad variety of SEDs in the optical-to-Spitzer bands of X-ray-selected AGNs means that AGNs selected according to the behavior in the optical/infrared will have to be supplemented by other kinds of data (e.g., X-ray) to produce unbiased samples of AGNs.
- ID:
- ivo://CDS.VizieR/J/A+A/522/A65
- Title:
- Lunar occultations at the ESO VLT
- Short Name:
- J/A+A/522/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lunar occultations (LO) are a very efficient and powerful technique that achieves the best combination of high angular resolution and sensitivity possible today at near-infrared wavelengths. Given that the events are fixed in time, that the sources are occulted randomly, and that the telescope use is minimal, the technique is very well suited for service mode observations. We have established a program of routine LO observations at the VLT observatory, especially designed to take advantage of short breaks available in-between other programs. We have used the ISAAC instrument in burst mode, capable of producing continuous read-outs at millisecond rates on a suitable subwindow. Given the random nature of the source selection, our aim has been primarily the investigation of a large number of stellar sources at the highest angular resolution in order to detect new binaries. Serendipitous results such as resolved sources and detection of circumstellar components were also anticipated.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A101
- Title:
- Lunar occultations of 184 stellar sources
- Short Name:
- J/A+A/532/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lunar occultations (LO) provide a unique combination of high angular resolution and sensitivity at near-infrared wavelengths. At the ESO Very Large Telescope, it is possible to achieve about 1 milliarcsecond (mas) resolution and detect sources as faint as K~12mag. We have taken advantage of a passage of the Moon over two crowded and reddened regions in the direction of the inner part of the Galactic bulge to obtain a high number of occultation light curves over two half nights. Our goal was to detect and characterize new binary systems, and to investigate highly extincted and relatively unknown infrared sources in search of circumstellar shells and similar peculiarities. Our target list included a significant number of very late-type stars, but the majority of the sources was without spectral classification.
