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D. T. Frayer

Publications and source records attributed to D. T. Frayer.

87 records · Page 5Linked to original sources
arXiv2003

The Host Galaxies of Optical Bright QSOs: Molecular Gas in Z < 0.1 PG-QSOs

We present results of a CO(1-0) line survey in a complete sample of 12 low redshift (Z < 0.1), optically bright QSOs (PG QSOs with M_B < -23 mag). Six new CO detections are reported here at levels exceeding I_CO ~2 Jy km/s. Combined with three previously reported detections, we find that 9 of the 12 QSOs have abundant, dense ISMs characteristic of late type galaxies. In all 9 of the detected QSOs, the derived molecular gas masses are M(H2) > 1.0e9 M_solar, with the most massive being 1e10 M_solar ~(PG 0050+124 -- I Zw 1). In the three sources not yet detected in CO, the upper limits on the gas masses are ~ 1e9 M_solar and thus we cannot rule out abundant ISMs even in these objects. Since our sample was chosen entirely on the basis of low redshift and optical luminosity (and not selected for strong infrared emission), we conclude that the majority of luminous, low redshift QSOs have gas-rich host galaxies and therefore can not be normal elliptical galaxies.

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arXiv2001

A Molecular Gas of z<0.2 Infrared-Excess, Optical QSOs

Millimeter-wave (CO) observations of optically-selected QSOs are potentially a powerful tool for studying the properties of both the QSOs and their host galaxies. We summarize here a recent molecular gas survey of z<0.17 optical QSOs with infrared (IR) excess, L_IR (8-1000 um) / L_bbb (0.1-1.0 um) > 0.36. Eight of these QSOs have been detected to date in CO(1-0), and the derived molecular gas masses are in the range 1.7-35x10^9 M_sun. The high L_IR / L'_CO of QSOs relative to the bulk of the local (z<0.2) IR luminous galaxy merger population is indicative of significant heating of dust (L_IR) by the QSO nucleus and/or by massive stars created in the host galaxy with high efficiency (i.e., per unit molecular gas, L'_CO).

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arXiv2001

Molecular Gas in Infrared-Excess, Optically-Selected QSOs and the Connection with Infrared Luminous Galaxies

The initial results of a millimeter (CO) survey of infrared-excess, optically-selected quasars from the Palomar-Green (PG) Bright Quasar Survey (BQS) with redshifts in the range 0.04 < z < 0.17 are presented. These observations represent the first step towards establishing with a complete sample whether or not quasi-stellar objects (QSOs) reside in molecular gas-rich galaxies, as well as towards determining how the infrared and molecular gas properties of QSOs compare with those of ultraluminous infrared galaxies (ULIGs), which are a possible evolutionary precursor of QSOs. The sample consists of QSOs having absolute blue magnitudes, M_B <~ -22.0, and infrared excesses, L_IR (8-1000 um) /L_bbb (0.1-1.0 um) >0.36, where the contribution to the bolometric luminosity of infrared thermal dust emission for all PG QSOs is typically 20--40%. Six out of 10 of the QSOs observed are detected in the CO(1-0) emission line; two detections confirm previous, less sensitive detections of CO(1-0) in PG 1613+658 and PG 0838+770, and four additional QSOs are detected for the first time (PG 1119+120, PG 1351+640, PG 1415+451, and PG 1440+356). These six detections, plus two previous detections of CO in IZw1 and Mrk 1014, bring the total number of 0.04 < z < 0.17 infrared-excess PG QSOs detected in CO to date to eight, and provide possible evidence that, in addition to fueling star formation, molecular gas may also serve as a primary source of fuel for QSO activity...

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arXiv2000

CO and Near-Infrared Observations of High-Redshift Submillimeter Galaxies

I discuss our ongoing Owens Valley Millimeter Array observations and Keck near-infrared wavelength observations of the high-redshift sub-mm population of galaxies. These observations are important for our understanding of the distant universe since the sub-mm population accounts for a large fraction of the extragalactic background at mm/sub-mm wavelengths and contributes significantly to the total amount of star-formation and AGN activity at high redshift. The CO data suggest that the sub-mm galaxies are analogous to the gas-rich ultraluminous systems found in the local universe. Initial near-infrared data show that many of the sub-mm galaxies are faint-red sources which are undetected at ultraviolet/optical wavelengths. These results highlight the importance that future sensitive mm-wavelength instruments, such as the LMT and ALMA, will have on our understanding of the early evolution and formation of galaxies.

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arXiv2000

The Identification of the Submillimeter Galaxy SMM J00266+1708

We report the detection of 1.3mm continuum and near-infrared K-band (2.2-micron) emission from the submillimeter galaxy SMM J00266+1708. Although this galaxy is among the brightest sub-mm sources detected in the blank-sky surveys (L~10^{13} L[sun]), SMM J00266+1708 had no reliable optical/near-infrared counter-part. We used sensitive interferometric 1.3mm observations with the Owens Valley Millimeter Array to accurately determine the position of the sub-mm galaxy. Follow-up near-infrared imaging with the Keck I telescope uncovered a new faint red galaxy at K=22.5 mag which is spatially coincident with the 1.3mm emission. This is currently the faintest confirmed counter-part of a sub-mm galaxy. Although the redshift of SMM J00266+1708 is still unknown, its high sub-mm/radio spectral index suggests that the system is at high redshift (z>2). Approximately 50% or more of the sub-mm galaxies are faint/red galaxies similar to that of SMM J00266+1708. These ultraluminous obscured galaxies account for a significant fraction of the total amount of star-formation at high redshift despite being missed by optical/ultraviolet surveys.

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arXiv2000

Millimetre/submillimetre-wave emission line searches for high-redshift galaxies

The redshifted spectral line radiation emitted from both atomic fine-structure and molecular rotational transitions in the interstellar medium (ISM) of high-redshift galaxies can be detected in the centimetre, millimetre and submillimetre wavebands. Here we predict the counts of galaxies detectable in an array of molecular and atomic lines. This calculation requires a reasonable knowledge of both the surface density of these galaxies on the sky, and the physical conditions in their ISM. The surface density is constrained using the results of submillimetre-wave continuum surveys. Follow-up OVRO Millimeter Array observations of two of the galaxies detected in the dust continuum have provided direct measurements of CO rotational line emission at redshifts of 2.56 and 2.81. Based on these direct high-redshift observations and on models of the ISM that are constrained by observations of low-redshift ultraluminous infrared galaxies, we predict the surface density of line-emitting galaxies as a function of line flux density and observing frequency. We incorporate the sensitivities and mapping speeds of existing and future millimetre/submillimetre-wave telescopes and spectrographs, and so assess the prospects for blank-field surveys to detect this line emission from gas-rich high-redshift galaxies.

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arXiv1999

Molecular Gas in High-Redshift Submillimeter Galaxies

We present observations of the luminous population of high-redshift sub-mm galaxies taken at the OVRO Millimeter Array. Studies of sub-mm galaxies are vital to our understanding of the formation and early evolution of galaxies since this population could account for a significant fraction of the total amount of star formation and AGN activity at high redshift. We discuss the CO detections for SMM J02399-0136 at z=2.8 and SMM J14011+0252 at z=2.6. The CO data show the presence of massive molecular gas reservoirs (M(H2) few X 10^{10}-10^{11} M(sun)) and suggest that the sub-mm galaxies are similar to low-redshift, gas-rich ultraluminous infrared galaxies. These results highlight the importance that future mm/sub-mm interferometric observations will have on our understanding of the high redshift universe.

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arXiv1999

Submillimeter Imaging of the Luminous Infrared Galaxy Pair VV 114

We report on 450- and 850-micron observations of the interacting galaxy pair, VV114E+W (IC1623), taken with the SCUBA camera on the James Clerk Maxwell Telescope, and near-infrared observations taken with UFTI on the UK Infrared Telescope. The system VV114 is in an early stage of a gas-rich merger. We detect submillimeter (sub-mm) emission extended over 30 arcsec (12 kpc) and find a good correlation between the spatial distribution of the sub-mm and CO emission. Both the CO and sub-mm emission peak near the reddest region of VV114E and extend toward VV114W. The bulk of the sub-mm emission resides in the central region showing the largest CO velocity gradients, which is thought to mark the kinematic centroid of the merger remnant. We derived a total dust mass of 1.2x10^{8} M_sun, assuming a power-law distribution of dust temperatures. The sub-mm observations suggest that the majority of the dust is relatively cool (T_d ~20--25 K), and the total dust mass is about 4 times higher than that inferred from the IRAS data alone. The system will likely evolve into a compact starburst similar to Arp220.

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arXiv1999

Molecular Gas in the z=2.565 Submillimeter Galaxy SMM J14011+0252

We report the detection of CO(3-2) emission from the submillimeter-selected luminous galaxy SMM J14011+0252. The optical counterpart of the submillimeter source has been identified as a merger system with spectral characteristics consistent with a starburst at z=2.565. The CO emission confirms the optical identification of the submillimeter source and implies a molecular gas mass of 5x10^{10}h_{75}^{-2} M(sun), after correcting for a lensing amplification factor of 2.75. The large molecular gas mass and the radio emission are consistent with the starburst interpretation of the source. These results are similar to those found for SMM J02399-0136, which was the first submillimeter selected CO source found at high redshift. The CO detections of these two high-redshift submillimeter galaxies suggest the presence of massive reservoirs of molecular gas which is consistent with the inferred high rates of star-formation (1000 M(sun)/yr). These two systems appear to be associated with merger events which may evolve into present day luminous elliptical galaxies.

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arXiv1998

Molecular Gas in the z=2.8 Submillimeter Galaxy SMM 02399-0136

We report the detection of CO(3-2) emission from the submillimeter-selected hyperluminous galaxy SMM 02399-0136. This galaxy is the brightest source detected in the recent SCUBA surveys of the submillimeter sky. The optical counterpart of the submillimeter source has been identified as a narrow-line AGN/starburst galaxy at z=2.8. The CO emission is unresolved, theta < 5 arcsec, and is coincident in redshift and position with the optical counterpart. The molecular gas mass derived from the CO observations is 8x10^{10} h_{75}^{-2} M_{sun}, after correcting for a lensing amplification factor of 2.5. The large CO luminosity suggests that a significant fraction of the infrared luminosity of SMM 02399-0136 arises from star formation. The high inferred star-formation rate of 10^{3} M_{sun}/yr and the large gaseous reservoir may suggest that we are seeing the formation phase of a massive galaxy. Future CO observations of other galaxies detected in deep submillimeter surveys will test the generality of these conclusions for the bulk of the faint submillimeter population.

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arXiv1998

HCO+ in the Starburst Galaxy M82

We report observations and an analysis of the distribution of HCO+(1-0) and HCO+(4-3) emission in the central 1 kpc star forming region of M82. Comparisons are made with other star formation indicators such as the mm continuum, the distribution of radio SNR's and the molecules CO and OH. In a broad sense, the HCO+ is distributed in a way similar to the CO, although there are noticeable differences in detail, including an inward displacement of spiral arm emission relative to CO. A comparison of the position-velocity plots for CO, HCO+(1-0), HCO+(4-3), and ionized gas, with orbits expected in the presence of the nuclear bar suggest an inward transfer of gas associated with star formation toward the nucleus. The HCO+(4-3)/(1-0) line ratios are comparatively uniform in the observed region, and according to an LVG analysis, reflect mean gas densities in the range 10^4 cm^{-3} - 10^5 cm^{-3} for kinetic temperatures in the range 20K - 60K. The comparative uniformity of these conditions and the low filling factor suggest that each sampled point comprises alarge number of clouds occupying a broad range of density, and possibly temperature. We briefly examine fractal type models in the context of the HCO+ data as an alternative way to analyze molecular line emission in M82.

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arXiv1998

Molecular Gas in Mrk 109: Constraining the O2/CO Ratio in Chemically Young Galaxies

We report on observations of CO(1-0) emission from the chemically young starburst galaxy Mrk 109. These observations were part of a study to constrain the O2/CO ratio in metal-deficient galaxies, which were motivated by theoretical work that suggests the possible enhancement of the O2/CO ratio in chemically young systems. Five low metallicity (Z < 0.5 Z(solar)) IRAS galaxies at redshifts z > 0.02 (required to shift the 118.75 GHz O2 line away from the atmospheric line) were searched for CO emission. We detected the CO line in only Mrk 109. From O2 observations of Mrk 109, we achieved an upper limit for the O2 column density abundance ratio of N(O2)/N(CO) < 0.31. These results provide useful constraints for the theoretical models of chemically young galaxies. We argue that either most of the molecular gas in Mrk 109 does not reside in dark clouds (Av >~ 5), or the standard equilibrium chemistry models are inadequate for metal-poor systems. The molecular gas mass implied by the CO observations of Mrk 109 is M(H2) ~= 4 x 10^{9} M(sun), and the CO data are consistent with a central starburst induced by the interaction with a nearby companion.

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arXiv1997

OH Satellite Line Masers in the Nucleus of NGC253

We report the detection of 1720 and 1612 MHz OH ground-state satellite line maser regions in the starburst galaxy NGC253. We find ten compact maser features all of which are located along the narrow ridge of bright radio continuum emission within the central 10 square arcseconds of the nucleus. The compact OH features appear physically associated with regions of dense molecular gas, supernova remnants, and HII regions. The data for several of the features are consistent with collisional inversion from the interaction of supernova remnant shocks with molecular gas, similar to that found for Galactic supernova remnants (Frail et al. 1996). For many other features near the nucleus of NGC253, we find conjugate behavior in the 1720 and 1612 MHz lines, with one line showing stimulated emission and the other showing stimulated absorption. These results suggest the importance of infrared pumping associated with the active star formation in NGC253 and is consistent with large column densities of molecular gas (N[H_2] >~ 10^{22}cm^{-2}).

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arXiv1997

OH Satellite Line Masers and an AGN Candidate in M82

We report the detection of OH satellite line masers at 1720 MHz and 1612 MHz from the nuclear region of the starburst galaxy M82. The observations were aimed at detecting 1720 MHz maser emission from the known radio emitting SNR in the nuclear region. At 1720 MHz we detect six features above the 5-sigma limit set by noise, four in emission and two in absorption. Three of the emission features appear closely associated with known discrete continuum radio sources, and one of the absorption features is precisely coincident with the discrete continuum source 44.01+59.6. The latter source also exhibits strong 1612 MHz emission at the same velocity. No other 1612 MHz features were detected. All of the 1720 MHz emission features are consistent with masers pumped by collisions with molecular hydrogen at densities between 10^3 cm^{-3} and 10^5 cm^{-3}, and T_k between 50 K and 250 K. The absorption and emission associated with the two satellite lines in 44.01+59.6, together with other evidence, points to the possibility that this source is the AGN in M82.

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