- ID:
- ivo://CDS.VizieR/II/295
- Title:
- Spitzer IRAC survey of the galactic center
- Short Name:
- II/295
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained Spitzer IRAC observations of the central 2.0{deg}x1.4{deg} (~280x200pc) of the Galaxy at 3.6-8.0um. A point-source catalog of 1065565 objects is presented. The catalog includes magnitudes for the point sources at 3.6, 4.5, 5.8, and 8.0um, as well as JHKs photometry from Two Micron All Sky Survey (2MASS). The point-source catalog is confusion limited with average limits of 12.4, 12.1, 11.7, and 11.2mag for [3.6], [4.5], [5.8], and [8.0], respectively. We find that the confusion limits are spatially variable because of stellar surface density, background surface brightness level, and extinction variations across the survey region. The overall distribution of point-source density with Galactic latitude and longitude is essentially constant, but structure does appear when sources of different magnitude ranges are selected. Bright stars show a steep decreasing gradient with Galactic latitude and a slow decreasing gradient with Galactic longitude, with a peak at the position of the Galactic center. From IRAC color-magnitude and color-color diagrams, we conclude that most of the point sources in our catalog have IRAC magnitudes and colors characteristic of red giant and asymptotic giant branch (AGB) stars.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/717/1181
- Title:
- Spitzer power-law galaxies in EGS
- Short Name:
- J/ApJ/717/1181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper analyzes a sample of 489 Spitzer/Infrared Array Camera (IRAC) sources in the Extended Groth Strip (EGS), whose spectral energy distributions fit a red power law (PL) from 3.6 to 8.0um. The median redshift for sources with known redshifts is <z>=1.6. Though all or nearly all of the sample galaxies are likely to be active galactic nuclei (AGNs), only 33% were detected in the EGS X-ray survey (AEGIS-X) using 200ks Chandra observations. The detected sources are X-ray luminous with L_X_>10^43^erg/s and moderately to heavily obscured with N_H_>10^22^cm^-2^. Stacking the X-ray-undetected sample members yields a statistically significant X-ray signal, suggesting that they are on average more distant or more obscured than sources with X-ray detections. The ratio of X-ray to mid-infrared fluxes suggests that a substantial fraction of the sources undetected in X-rays are obscured at the Compton-thick level, in contrast to the X-ray-detected sources, all of which appear to be Compton thin.
- ID:
- ivo://CDS.VizieR/J/AJ/135/726
- Title:
- Spitzer SAGE observations of LMC PNe
- Short Name:
- J/AJ/135/726
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAC and MIPS images and photometry of a sample of previously known planetary nebulae (PNe) from the Surveying the Agents of a Galaxy's Evolution (SAGE) survey of the Large Magellanic Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in the survey field, 185 objects were detected in at least two of the IRAC bands, and 161 detected in the MIPS 24um images. Color-color and color-magnitude diagrams are presented using several combinations of IRAC, MIPS, and Two Micron All Sky Survey magnitudes. The location of an individual PN in the color-color diagrams is seen to depend on the relative contributions of the spectral components which include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared forbidden line emission from the ionized gas, warm dust continuum, and emission directly from the central star. The sample of LMC PNe is compared to a number of Galactic PNe and found not to significantly differ in their position in color-color space. We also explore the potential value of IR PNe luminosity functions (LFs) in the LMC. IRAC LFs appear to follow the same functional form as the well-established [OIII] LFs although there are several PNe with observed IR magnitudes brighter than the cut-offs in these LFs.
- ID:
- ivo://CDS.VizieR/J/ApJS/187/149
- Title:
- StarCAT: STIS UV echelle spectra of stars
- Short Name:
- J/ApJS/187/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- StarCAT is a catalog of high resolution ultraviolet spectra of objects classified as "stars," recorded by Space Telescope Imaging Spectrograph (STIS) during its initial seven years of operations (1997-2004). StarCAT is based on 3184 echelle observations of 545 distinct targets, with a total exposure duration of 5.2Ms. For many of the objects, broad ultraviolet coverage has been achieved by splicing echellegrams taken in two or more FUV (1150-1700{AA}) and/or NUV (1600-3100{AA}) settings. In cases of multiple pointings on conspicuously variable sources, spectra were separated into independent epochs. Otherwise, different epochs were combined to enhance the signal-to-noise ratio (S/N). A post-facto correction to the "calstis" pipeline data sets compensated for subtle wavelength distortions identified in a previous study of the STIS calibration lamps. An internal "fluxing" procedure yielded coherent spectral energy distributions (SEDs) for objects with broadly overlapping wavelength coverage. The best StarCAT material achieves 300m/s internal velocity precision; absolute accuracy at the 1km/s level; photometric accuracy of order 4%; and relative flux precision several times better (limited mainly by knowledge of SEDs of UV standard stars). While StarCAT represents a milestone in the large-scale post-processing of STIS echellegrams, a number of potential improvements in the underlying "final" pipeline are identified.
- ID:
- ivo://CDS.VizieR/J/ApJ/683/822
- Title:
- Star formation in Ophiuchus and Perseus II.
- Short Name:
- J/ApJ/683/822
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these data sets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1M_{sun}_).
- ID:
- ivo://CDS.VizieR/J/A+A/303/661
- Title:
- Star-forming galaxies in the Coma Cluster
- Short Name:
- J/A+A/303/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a field of 1deg radius centered in the Coma cluster of galaxies, UV ({lambda}=2000 A) observations with a 40-cm balloon-borne imaging telescope (FOCA) have provided a list of 442 UV sources brighter than m_UV_=18, which are identified in the Godwin (1983) catalogue. 254 are identified as galaxies, 178 as star-like objects and 10 as galaxy-star pairs, unresolved in the UV image.
- ID:
- ivo://CDS.VizieR/J/ApJ/730/88
- Title:
- Star-forming regions in NGC 6822 from UV data
- Short Name:
- J/ApJ/730/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the star formation in the low-metallicity galaxy NGC 6822 over the past few hundred million years, using GALEX far-UV (FUV, 1344-1786{AA}) and near-UV (NUV, 1771-2831{AA}) imaging, and ground-based H{alpha} imaging. From the GALEX FUV image, we define 77 star-forming (SF) regions with area >860pc^2^, and surface brightness <~26.8 mag (AB) arcsec^-2^, within 0.2{deg} (1.7kpc) of the center of the galaxy. We estimate the extinction by interstellar dust in each SF region from resolved photometry of the hot stars it contains: E(B-V) ranges from the minimum foreground value of 0.22mag up to 0.66+/-0.21mag. The integrated FUV and NUV photometry, compared with stellar population models, yields ages of the SF complexes up to a few hundred Myr, and masses from 2x10^2^M_{sun}_ to 1.5x10^6^M_{sun}_. The derived ages and masses strongly depend on the assumed type of interstellar selective extinction, which we find to vary across the galaxy. The total mass of the FUV-defined SF regions translates into an average star formation rate (SFR) of 1.4x10^-2^M_{sun}_/yr over the past 100Myr, and SFR=1.0x10^-2^M_{sun}_/yr in the most recent 10Myr. The latter is in agreement with the value that we derive from the H{alpha} luminosity, SFR=0.008M_{sun}_/yr. The SFR in the most recent epoch becomes higher if we add the SFR=0.02M_{sun}_/yr inferred from far-IR measurements, which trace star formation still embedded in dust (age <~ a few Myr).
- ID:
- ivo://CDS.VizieR/J/AJ/110/2747
- Title:
- Stars in Sculptor dwarf spheroidal galaxy
- Short Name:
- J/AJ/110/2747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using 26 plates taken over the course of more than half a century, we present proper motions and photometry for 1177 stars in the central region of the Sculptor dwarf spheroidal galaxy, down to a limiting magnitude of V~20.25 at the level of the horizontal branch. The proper-motion cleaned color-magnitude diagram retained a broad giant branch, further supporting an intrinsic spread in metallicity. We determined an absolute proper motion for Sculptor, relative to background galaxies, of mu_alpha=+0.036+/-0.022arcsec/century and mu_delta=0.043+/-0.025arcsec/century after correcting for the LSR and peculiar solar motions. Our proper-motion uncertainty is similar to or smaller than those obtained by different groups for other distant satellites of the Galaxy. When combined with Sculptor's distance and radial velocity, this measurement shows the dwarf spheroidal to have a space velocity of roughly 220+/-125km/s. Although our measurement is less than twice its uncertainty, the direction of Sculptor's motion is significant because it rules out motion along the Magellanic Stream. A 2.5 sigma error allows for motion in a direction toward the Fornax dwarf spheroidal galaxy, so Sculptor remains a possible member of the proposed Fornax-Leo-Sculptor stream.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A125
- Title:
- Stellar content of the XMM-Newton slew survey
- Short Name:
- J/A+A/614/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the stellar content of the current version of the XMM-Newton slew survey (XMMSL2). Since stars emit only a small fraction of their total luminosity in the X-ray band, the stellar XMMSL2 sources ought to have relatively bright optical counterparts. Therefore the stellar identifications were obtained by an automatic crossmatch of the XMMSL2 catalog with the first Gaia data release (Gaia DR1), 2MASS, and Tycho2 catalogs. The reliability of this procedure was verified by a comparison with the individually classified Einstein Observatory medium sensitivity survey X-ray sources and by a crossmatch with the Chandra Source Catalog. We identify 6815 of the 23252 unique XMMSL2 sources to be stellar sources, while 893 sources are flagged as unreliable. For every counterpart a matching probability is estimated based upon the distance between the XMMSL2 source and the counterpart. Given this matching probability the sample is expected to be reliable to 96.7% and complete to 96.3%. The sample contains stars of all spectral types and luminosity classes, and late-type dwarfs have the largest share. For many stellar sources the fractional contribution of the X-ray band to the total energy output is found above the saturation limit of previous studies (L_X_/L_bol_=10^-3^), because the XMMSL2 sources are more affected by flares owing to their short exposure times of typically 6s. A comparison with the second ROSAT all-sky survey (2RXS) source catalog shows that about 25% of the stellar XMMSL2 sources are previously unknown X-ray sources. The results of our identification procedure can be accessed via VizieR.
- ID:
- ivo://CDS.VizieR/J/AJ/105/980
- Title:
- Stellar content of Tr 14 and Tr 16
- Short Name:
- J/AJ/105/980
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of the region around {eta} Car is investigated using CCD photometry and spectroscopy.
